Boat voyage to Silhet—River—Palms—Teelas—Botany—Fish weirs—Forests of
Cachar—Sandal-wood, etc.—Porpoises—Alligators—Silchar—Tigers—Rice
crops—Cookies—Munniporees—Hockey—Varnish—Dance—Nagas—Excursion to
Munnipore frontier—Elephant bogged—Bamboos—_Cardiopteris_—Climate,
etc., of Cachar—Mosquitos—Fall of
banks—Silhet—Oaks—_Stylidium_—Tree-ferns—Chattuc—Megna—Meteorology—
Palms—Noacolly—Salt-smuggling—Delta of Ganges and Megna—Westward
progress of Megna—Peat—Tide—Waves—Earthquakes—Dangerous
navigation—Moonlight scenes—Mud island—Chittagong—Mug
tribes—Views—Trees—Churs—Flagstaff hill—Coffee—Pepper—Tea,
etc.—Excursions from Chittagong—_Dipterocarpi_ or Gurjun oil
trees—Earthquake—Birds—Papaw—Bleeding of stems—Poppy and Sun
fields—Seetakoond—Bungalow and hill—Perpetual
flame—_Falconeria—Cycas_—Climate—Leave for Calcutta—Hattiah
island—Plants—Sunderbunds—Steamer—Tides—_Nipa
fruticans_—Fishing—Otters—Crocodiles—_Phœnix paludosa_—Departure from
India.
We left Churra on the 17th of November, and taking boats at Pundua,
crossed the Jheels to the Soormah, which we ascended to Silhet. Thence
we continued our voyage 120 miles up the river in canoes, to Silchar,
the capital of the district of Cachar: the boats were such as I
described at Chattuc, and though it was impossible to sit upright in
them, they were paddled with great swiftness. The river at Silhet is
200 yards broad; it is muddy, and flows with a gentle current of two to
three miles an hour, between banks six to twelve feet high. As we
glided up its stream, villages became rarer, and eminences more
frequent in the Jheels. The people are a tall, bold, athletic Mahometan
race, who live much on the water, and cultivate rice, sesamum, and
radishes, with betel-pepper in thatched enclosures as in Sikkim: maize
and sugar are rarer, bamboos abound, and four palms (_Borassus, Areca,_
cocoa-nut, and _Caryota_) are planted, but there are no date-palms.
The Teelas (or hillocks) are the haunts of wild boars, tigers, and
elephants, but not of the rhinoceros; they are 80 to 200 feet high, of
horizontally stratified gravel and sand, slates, and clay
conglomerates, with a slag-like honey-combed sandstone; they are
covered with oaks, figs, _Heretiera,_ and bamboos, and besides a
multitude of common Bengal plants, there are some which, though
generally considered mountain or cold country genera, here descend to
the level of the sea; such are _Kadsura, Rubus, Camellia,_ and _Sabia_;
_Aerides_ and _Saccolabia_ are the common orchids, and rattan-canes and
_Pandani_ render the jungles impenetrable.
A very long sedge (_Scleria_) grows by the water, and is used for
thatching: boatloads of it are collected for the Calcutta market, for
which also were destined many immense rafts of bamboo, 100 feet long.
The people fish much, using square and triangular drop-nets stretched
upon bamboos, and rude basket-work weirs, that retain the fish as the
river falls. Near the villages we saw fragments of pottery three feet
below the surface of the ground, shewing that the bank, which is higher
than the surrounding country, increases from the annual overflow.
About seventy miles up the river, the mountains on the north, which are
east of Jyntea, rise 4000 feet high in forest-clad ranges like those of
Sikkim. Swamps extend from the river to their base, and penetrate their
valleys, which are extremely malarious: these forests are frequented by
timber-cutters, who fell jarool (_Lagerstrœmia Reginæ_), a magnificent
tree with red wood, which, though soft, is durable under water, and
therefore in universal use for boat-building. The toon is also cut,
with red sandal-wood (_Adenanthera pavonina_); also Nageesa,[373]
_Mesua ferrea,_ which is highly valued for its weight, strength, and
durability: _Aquilaria agallocha,_ the eagle-wood, a tree yielding
uggur oil, is also much sought for its fragrant wood, which is carried
to Silhet and Azmerigunj, where it is broken up and distilled. Neither
teak, sissoo, sal, nor other _Dipterocarpi,_ are found in these
forests.
[373] There is much dispute amongst oriental scholars about the word
Nageesa; the Bombay philologists refer it to a species of _Garcinia,_
whilst the pundits on the Calcutta side of India consider it to be
_Mesua ferrea._ Throughout our travels in India, we were struck with
the undue reliance placed on native names of plants, and information
of all kinds; and the pertinacity with which each linguist adhered to
his own crotchet as to the application of terms to natural objects,
and their pronunciation. It is a very prevalent, but erroneous,
impression, that savage and half-civilised people have an accurate
knowledge of objects of natural history, and a uniform nomenclature
for them.
Porpoises, and both the long and the short-nosed alligator, ascend the
Soormah for 120 miles, being found beyond Silchar, which place we
reached on the 22nd, and were most hospitably received by Colonel
Lister, the political agent commanding the Silhet Light Infantry, who
was inspecting the Cookie levy, a corps of hill-natives which had
lately been enrolled.
The station is a small one, and stands about forty feet above the
river, which however rises half that height in the rains. Long low
spurs of tertiary rocks stretch from the Tipperah hills for many miles
north, through the swampy Jheels to the river; and there are also hills
on the opposite or north side, but detached from the Cookie hills, as
the lofty blue range twelve miles north of the Soormah is called. All
these mountains swarm with tigers, wild buffalos, and boars, which also
infest the long grass of the Jheels.
The elevation of the house we occupied at Silchar was 116 feet above
the sea. The bank it stood on was of clay, with soft rocks of
conglomerate, which often assume the appearance of a brown sandy slag.
During the first Birmese war, Colonel Lister was sent with a force up
to this remote corner of Bengal, when the country was an uninhabited
jungle, so full of tigers that not a day passed without one or more of
his grass or wood-cutters being carried off. Now, thousands of acres
are cultivated with rice, and during our stay we did not see a tiger.
The quantity of land brought into cultivation in this part of Bengal,
and indeed throughout the Gangetic delta, has probably been doubled
during the last twenty years, and speaks volumes for the state of the
peasant under the Indian Company’s sway, as compared with his former
condition. The Silchar rice is of admirable quality, and much is
imported to Silhet, the Jheels not producing grain enough for the
consumption of the people. Though Silchar grows enough for ten times
its population, there was actually a famine six weeks before our
arrival, the demand from Silhet being so great.
The villages of Cachar are peopled by Mahometans, Munniporees, Nagas,
and Cookies; the Cacharies themselves being a poor and peaceful jungle
tribe, confined to the mountains north of the Soormah. The
Munniporees[374] are emigrants from the kingdom of that name, which
lies beyond the British possessions, and borders on Assam and Birmah.
Low ranges of forest-clad mountains at the head of the Soormah,
separate it from Silchar, with which it is coterminous; the two chief
towns being seven marches apart. To the south-east of Silchar are
interminable jungles, peopled by the Cookies, a wild Indo-Chinese
tribe, who live in a state of constant warfare, and possess the whole
hill-country from this, southward to beyond Chittagong. Two years ago
they invaded and ravaged Cachar, carrying many of the inhabitants into
slavery, and so frightening the people, that land previously worth six
rupees a biggah, is now reduced to one and a half. Colonel Lister was
sent with a strong party to rescue the captives, and marched for many
days through their country without disturbing man or beast; penetrating
deep forests of gigantic trees and tall bamboos, never seeing the sun
above, or aught to the right and left, save an occasional clearance and
a deserted village. The incursion, however, had its effects, and the
better inclined near the frontier have since come forward, and been
enrolled as the Cookie levy.
[374] The Munnipore valley has never been explored by any naturalist,
its mountains are said to be pine-clad, and to rise 8000 feet above
the level of the sea. The Rajah is much harassed by the Birmese, and
is a dependant of the British, who are in the very frequent dilemma of
supporting on the throne a sovereign opposed by a strong faction of
his countrymen, and who has very dubious claims to his position.
During our stay at Silchar, the supposed rightful Rajah was prevailing
over the usurper; a battle had been fought on the hills on the
frontier, and two bodies floated past our bungalow, pierced with
arrows.
The Munnipore emigrants are industrious settlers for a time, but never
remain long in one place: their religion is Hindoo, and they keep up a
considerable trade with their own country, whence they import a large
breed of buffalos, ponies, silks, and cotton cloths dyed with arnotto
(_Bixa_), and universally used for turbans. They use bamboo
blowing-tubes and arrows for shooting birds, make excellent shields of
rhinoceros hide (imported from Assam), and play at hockey on horseback
like the Western Tibetans. A fine black varnish from the fruit of
_Holigarna longifolia,_ is imported from Munnipore, as is another made
from _Sesuvium Anacardium_ (marking-nut), and a remarkable black
pigment resembling that from _Melanorhœa usitatissima,_ which is white
when fresh, and requires to be kept under water.[375]
[375] This turns of a beautiful black colour when applied to a
surface, owing, according to Sir D. Brewster, to the fresh varnish
consisting of a congeries of minute organised particles, which
disperse the rays of light in all directions; the organic structure is
destroyed when the varnish dries and the rays of light are
consequently transmitted.
One fine moonlight night we went to see a Munnipore dance. A large
circular area was thatched with plantain leaves, growing on their
trunks, which were stuck in the ground; and round the enclosure was a
border neatly cut from the white leaf-sheaths of the same tree. A
double enclosure of bamboo, similarly ornamented, left an inner circle
for the performers, and an outer for the spectators: the whole was
lighted with oil lamps and Chinese paper lanterns. The musicians sat on
one side, with cymbals, tomtoms, and flutes, and sang choruses.
The performances began by a copper-coloured Cupid entering and calling
the virgins with a flute; these appeared from a green-room, to the
number of thirty or forty, of all ages and sizes. Each had her hair
dressed in a topknot, and her head covered with a veil; a scarlet
petticoat loaded with tinsel concealed her naked feet, and over this
was a short red kirtle, and an enormous white shawl was swathed round
the body from the armpits to the waist. A broad belt passed over the
right shoulder and under the left arm, to which hung gold and silver
chains, corals, etc., with tinsel and small mirrors sewed on
everywhere: the arms and hands were bare, and decorated with bangles
and rings.
Many of the women were extremely tall, great stature being common
amongst the Munniporees. They commenced with a prostration to Cupid,
around whom they danced very slowly, with the arms stretched out, and
the hands in motion; at each step the free foot was swung backwards and
forwards. Cupid then chose a partner, and standing in the middle went
through the same motions, a compliment the women acknowledged by
curtseying and whirling round, making a sort of cheese with their
petticoats, which, however, were too heavy to inflate properly.
The Nagas are another people found on this frontier, chiefly on the
hills to the north: they are a wild, copper-coloured, uncouth jungle
tribe, who have proved troublesome on the Assam frontier. Their
features are more Tartar than those of the Munniporees, especially
amongst the old men. They bury their dead under the threshold of their
cottages. The men are all but naked, and stick plumes of hornbills’
feathers in their hair, which is bound with strips of bamboo: tufts of
small feathers are passed through their ears, and worn as shoulder
lappets. A short blue cotton cloth, with a fringe of tinsel and tufts
of goat’s hair dyed red, is passed over the loins in front only: they
also wear brass armlets, and necklaces of cowries, coral, amber, ivory,
and boar’s teeth. The women draw a fringed blue cloth tightly across
the breast, and wear a checked or striped petticoat. They are less
ornamented than the men, and are pleasing looking; their hair is
straight, and cut short over the eyebrows.
The Naga dances are very different from those of the Munniporees; being
quick, and performed in excellent time to harmonious music. The figures
are regular, like quadrilles and country-dances: the men hold their
knives erect during the performance, the women extend their arms only
when turning partners, and then their hands are not given, but the
palms are held opposite. The step is a sort of polka and balancez, very
graceful and lively. A bar of music is always played first, and at the
end the spectators applaud with two short shouts. Their ear for music,
and the nature of their dance, are as Tibetan as their countenances,
and different from those of the Indo-Chinese tribes of the frontier.
We had the pleasure of meeting Lieutenant Raban at Silchar, and of
making several excursions in the neighbourhood with him; for which
Colonel Lister here, as at Churra, afforded us every facility of
elephants and men. Had we had time, it was our intention to have
visited Munnipore, but we were anxious to proceed to Chittagong. I
however made a three days’ excursion to the frontier, about thirty
miles distant, proceeding along the north bank of the Soormah. On the
way my elephant got bogged in crossing a deep muddy stream: this is
sometimes an alarming position, as should the animal become terrified,
he will seize his rider, or pad, or any other object (except his
driver), to place under his knees to prevent his sinking. In this
instance the driver in great alarm ordered me off, and I had to
flounder out through the black mud. The elephant remained fast all
night, and was released next morning by men with ropes.
The country continued a grassy level, with marshes and rice
cultivation, to the first range of hills, beyond which the river is
unnavigable; there also a forest commences, of oaks, figs, and the
common trees of east Bengal. The road hence was a good one, cut by
Sepoys across the dividing ranges, the first of which is not 500 feet
high. On the ascent bamboos abound, of the kind called Tuldah or
Dulloah, which has long very thin-walled joints; it attains no great
size, but is remarkably gregarious. On the east side of the range, the
road runs through soft shales and beds of clay, and conglomerates,
descending to a broad valley covered with gigantic scattered
timber-trees of jarool, acacia, _Diospyros, Urticeæ,_ and _Bauhiniæ,_
rearing their enormous trunks above the bamboo jungle: immense
rattan-canes wound through the forest, and in the gullies were groves
of two kinds of tree-fern, two of _Areca, Wallichia_ palm, screw-pine,
and _Dracæna._ Wild rice grew abundantly in the marshes, with tall
grasses; and _Cardiopteris_[376] covered the trees for upwards of sixty
feet, like hops, with a mass of pale-green foliage, and dry white
glistening seed-vessels. This forest differed from those of the Silhet
and Khasia mountains, especially in the abundance of bamboo jungle,
which is, I believe, the prevalent feature of the low hills in Birmah,
Ava, and Munnipore; also in the gigantic size of the rattans, 1arger
palms, and different forest trees, and in the scanty undergrowth of
herbs and bushes. I only saw, however, the skirts of the forest; the
mountains further east, which I am told rise several thousand feet in
limestone cliffs, are doubtless richer in herbaceous plants.
[376] A remarkable plant of unknown affinity; see Brown and Bennett,
“Flora Java:” it is found in the Assam valley and Chittagong.
The climate of Cachar partakes of that of the Jheels in its damp
equable character: during our stay the weather was fine, and dense fogs
formed in the morning: the mean maximum was 80°, minimum 58·4°.[377]
[377] The temperature does not rise above 90° in summer, nor sink
below 45° or 50° in January: forty-seven comparative observations with
Calcutta showed the mean temperature to be 1·8° lower at Silchar, and
the air damper, the saturation point being, at Calcutta 0·3791, at
Silchar 0·4379.
The annual rain-fall in 1850 was 111·60 inches, according to a register
kindly given me by Captain Verner. There are few mosquitos, which is
one of the most curious facts in the geographical distribution of these
capricious bloodsuckers; for the locality is surrounded by swamps, and
they swarm at Silhet, and on the river lower down. Both on the passage
up and down, we were tormented in our canoes by them for eighty or
ninety miles above Silhet, and thence onwards to Cachar we were free.
On the 30th of November, we were preparing for our return to Silhet,
and our canoes were loading, when we were surprised by a loud rushing
noise, and saw a high wave coming down the river, swamping every boat
that remained on its banks, whilst most of those that pushed out into
the stream, escaped with a violent rocking. It was caused by a slip of
the bank three quarters of a mile up the stream, of no great size, but
which propagated a high wave. This appeared to move on at about the
rate of a mile in three or four minutes, giving plenty of time for our
boatmen to push out from the land on hearing the shouts of those first
overtaken by the calamity; but they were too timid, and consequently
one of our canoes, full of papers, instruments, and clothes, was
swamped. Happily our dried collections were not embarked, and the hot
sun repaired much of the damage.
We left in the evening of the 2nd of December, and proceeded to Silhet,
where we were kindly received by Mr. Stainforth, the district judge.
Silhet, the capital of the district of the same name, is a large
Mahometan town, occupying a slightly raised part of the Jheels, where
many of the Teelas seem joined together by beds of gravel and sand. In
the rains it, is surrounded by water, and all communication with other
parts is by boats: in winter, Jynteapore and Pundua may be reached by
land, crossing creeks innumerable on the way. Mr. Stainforth’s house,
like those of most of the other Europeans, occupies the top of one of
the Teelas, 150 feet high, and is surrounded by fine spreading
oaks,[378] _Garcinia,_ and _Diospyros_ trees. The rock of which the
hill is composed, is a slag-like ochreous sandstone, covered in most
places with a shrubbery of rose-flowered _Melastoma,_ and some peculiar
plants.[379]
[378] It is not generally known that oaks are often very tropical
plants; not only abounding at low elevations in the mountains, but
descending in abundance to the level of the sea. Though unknown in
Ceylon, the Peninsula of India, tropical Africa, or South America,
they abound in the hot valleys of the Eastern Himalaya, East Bengal,
Malay Peninsula, and Indian islands; where perhaps more species grow
than in any other part of the world. Such facts as this disturb our
preconceived notions of the geographical distribution of the most
familiar tribes of plants, and throw great doubt on the conclusions
which fossil plants are supposed to indicate.
[379] _Gelonium, Adelia, Moacurra, Linostoma, Justicia, Trophis,
Connarus, Ixora, Congea, Dalhousiea, Grewia, Myrsine, Buttneria_; and
on the shady exposures a _Calamus, Briedelia,_ and various ferns.
Broad flat valleys divide the hills, and are beautifully clothed with a
bright green jungle of small palms, and many kinds of ferns. In sandy
places, blue-flowered _Burmannia, Hypoxis,_ and other pretty tropical
annuals, expand their blossoms, with an inconspicuous _Stylidium,_ a
plant belonging to a small natural family, whose limits are so confined
to New Holland, that this is almost the only kind that does not grow in
that continent. Where the ground is swampy, dwarf _Pandanus_ abounds,
with the gigantic nettle, _Urtica crenulata_ (“Mealum-ma” of Sikkim,
see p. 189).
The most interesting botanical ramble about Silhet is to the tree-fern
groves on the path to Jynteapore, following the bottoms of shallow
valleys between the Teelas, and along clear streams, up whose beds we
waded for some miles, under an arching canopy of tropical shrubs,
trees, and climbers, tall grasses, screw-pines, and _Aroideæ._ In the
narrower parts of the valleys the tree-ferns are numerous on the
slopes, rearing their slender brown trunks forty feet high, with
feathery crowns of foliage, through which the sun-beams trembled on the
broad shining foliage of the tropical herbage below.
Silhet, though hot and damp, is remarkably healthy, and does not differ
materially in temperature from Silchar, though it is more equable and
humid.[380] It derives some interest from having been first brought
into notice by the enterprise of one of the Lindsays of Balcarres, at a
time when the pioneers of commerce in India encountered great hardships
and much personal danger. Mr. Lindsay, a writer in the service of the
East India Company, established a factory at Silhet, and commenced the
lime trade with Calcutta,[381] reaping an enormous fortune himself, and
laying the foundation of that prosperity amongst the people which has
been much advanced by the exertions of the Inglis family, and has
steadily progressed under the protecting rule of the Indian government.
[380] During our stay of five days the mean maximum temperature was
74°, minimum 64·8°: that of thirty-two observations compared with
Calcutta show that Silhet is only 1·7° cooler, though Mr. Stainforth’s
house is upwards of 2° further north, and 160 feet more elevated. A
thermometer sunk two feet seven inches, stood at 73·5°. The relative
saturation-points were, Calcutta ·633, Silhet ·821.
[381] For an account of the early settlement of Silhet, see “Lives of
the Lindsays,” by Lord Lindsay.
From Silhet we took large boats to navigate the Burrampooter and Megna,
to their embouchure in the Bay of Bengal at Noacolly, a distance of 250
miles, whence we were to proceed across the head of the bay to
Chittagong, about 100 miles farther. We left on the 7th of December,
and arrived at Chattuc on the 9th, where we met our Khasia collectors
with large loads of plants, and paid them off. The river was now low,
and presented a busy scene, from the numerous trading boats being
confined to its fewer and deeper channels. Long grasses and sedges
(_Arundo, Saccharum_ and _Scleria_), were cut, and stacked along the
water’s edge, in huge brown piles, for export and thatching.
On the 13th December, we entered the broad stream of the Megna. Rice is
cultivated along the mud flats left by the annual floods, and the banks
are lower and less defined than in the Soormah, and support no long
grasses or bushes. Enormous islets of living water-grasses (_Oplismenus
stagninus_) and other plants, floated past, and birds became more
numerous, especially martins and egrets. The sun was hot, but the
weather otherwise cool and pleasant: the mean temperature was nearly
that of Calcutta, 69·7°, but the atmosphere was more humid.[382]
[382] The river-water was greenish, and a little cooler (73·8°) than
that of the Soormah (74·3°), which was brown and muddy. The barometer
on the Soormah stood 0·028 inch higher than that of Calcutta (on the
mean of thirty-eight observations), whereas on the Megna the pressure
was 0·010 higher. As Calcutta is eighteen feet above the level of the
Bay of Bengal, this shows that the Megna (which has no perceptible
current) is at the level of the sea, and that either the Soormah is
upwards of thirty feet above that level, or that the atmospheric
pressure there, and at this season, is less than at Calcutta, which,
as I have hinted at p. 259, is probably the case.
On the 14th we passed the Dacca river; below which the Megna is several
miles wide, and there is an appearance of tide, from masses of purple
_Salvinia_ (a floating plant, allied to ferns), being thrown up on the
beach like sea-weed. Still lower down, the vegetation of the
Sunderbunds commences; there is a narrow beach, and behind it a mud
bank several feet high, supporting a luxuriant green jungle of palms
(_Borassus_ and _Phœnix_), immense fig-trees, covered with _Calami,_
and tall betel-palms, clothed with the most elegant drapery of
_Arostichum scandens,_ a climbing fern with pendulous fronds.
Towards the embouchure, the banks rise ten feet high, the river expands
into a muddy sea, and a long swell rolls in, to the disquiet of our
fresh-water boatmen. Low islands of sand and mud stretch along the
horizon: which, together with the ships, distorted by extraordinary
refraction, flicker as if seen through smoke. Mud is the all prevalent
feature; and though the water is not salt, we do not observe in these
broad deltas that amount of animal life (birds, fish, alligators, and
porpoises), that teems in the narrow creeks of the western Sunderbunds.
We landed in a canal-like creek at Tuktacolly,[383] on the 17th, and
walked to Noacolly, over a flat of hard mud or dried silt, covered with
turf of _Cynodon Dactylon._ We were hospitably received by Dr. Baker, a
gentleman who has resided here for twenty-three years; and who
communicated to us much interesting information respecting the features
of the Gangetic delta.
[383] “Colly” signifies a muddy creek, such as intersect the delta.
Noacolly is a station for collecting the revenue and preventing the
manufacture of salt, which, with opium, are the only monopolies now in
the hands of the East India Company. The salt itself is imported from
Arracan, Ceylon, and even Europe, and is stored in great wooden
buildings here and elsewhere. The ground being impregnated with salt,
the illicit manufacture by evaporation is not easily checked; but
whereas the average number of cases brought to justice used to be
twenty and thirty in a week, they are now reduced to two or three. It
is remarkable, that though the soil yields such an abundance of this
mineral, the water of the Megna at Noacolly is only brackish, and it is
therefore to repeated inundations and surface evaporations that the
salt is due. Fresh water is found at a very few feet depth everywhere,
but it is not good.
When it is considered how comparatively narrow the sea-board of the
delta is, the amount of difference in the physical features of the
several parts, will appear most extraordinary. I have stated that the
difference between the northern and southern halves of the delta is so
great, that, were all depressed and their contents fossilised, the
geologist who examined each by itself, would hardly recognise the two
parts as belonging to one epoch; and the difference between the east
and west halves of the lower delta is equally remarkable.
The total breadth of the delta is 260 miles, from Chittagong to the
mouth of the Hoogly, divided longitudinally by the Megna: all to the
west of that river presents a luxuriant vegetation, while to the east
is a bare muddy expanse, with no trees or shrubs but what are planted
On the west coast the tides rise twelve or thirteen feet, on the east,
from forty to eighty. On the west, the water is salt enough for
mangroves to grow for fifty miles up the Hoogly; on the east, the sea
coast is too fresh for that plant for ten miles south of Chittagong. On
the west, fifty inches is the Cuttack fall of rain; on the east, 90 to
120 at Noacolly and Chittagong, and 200 at Arracan. The east coast is
annually visited by earthquakes, which are rare on the west; and
lastly, the majority of the great trees and shrubs carried down from
the Cuttack and Orissa forests, and deposited on the west coast of the
delta, are not only different in species, but in natural order, from
those that the Fenny and Chittagong rivers bring down from the
jungles.[384]
[384] The Cuttack forests are composed of teak, Sal, Sissoo, ebony,
_Pentaptera, Buchanania,_ and other trees of a dry soil, and that
require a dry season alternating with a wet one. These are unknown in
the Chittagong forests, which have Jarool (_Lagerstrœmia_) _Mesua,
Dipterocarpi,_ nutmegs, oaks of several kinds, and many other trees
not known in the Cuttack forests, and all typical of a perennially
humid atmosphere.
We were glad to find at Noacolly that our observations on the
progression westwards of the Burrampooter (see p. 253) were confirmed
by the fact that the Megna also is gradually moving in that direction,
leaving much dry land on the Noacolly side, and forming islands
opposite that coast; whilst it encroaches on the Sunderbunds, and is
cutting away the islands in that direction. This advance of the fresh
waters amongst the Sunderbunds is destructive to the vegetation of the
latter, which requires salt; and if the Megna continues its slow course
westwards, the obliteration of thousands of square miles of a very
peculiar flora, and the extinction of many species of plants and
animals that exist nowhere else, may ensue. In ordinary cases these
plants, etc., would take up their abode on the east coast, as they were
driven from the west; but such might not be the case in this delta; for
the sweeping tides of the east coast prevent any such vegetation
establishing itself there, and the mud which the eastern rivers carry
down, becomes a caking dry soil, unsuited to the germination of seeds.
On our arrival at Calcutta in the following February, Dr. Falconer
showed us specimens of very modern peat, dug out of the banks of the
Hoogly a few feet below the surface of the soil, in which were seeds of
the _Euryale ferox_:[385] this plant is not now known to be found
nearer than Dacca (sixty miles north-east, see p. 255), and indicates a
very different state of the surface at Calcutta at the date of its
deposition than that which exists now, and also shows that the estuary
was then much fresher.
[385] This peat Dr. Falconer also found to contain bones of birds and
fish, seeds of _Cucumis Madraspatana_ and another Cucurbitaceous
plant, leaves of _Saccharum Sara_ and _Ficus cordifolia._ Specks of
some glistening substance were scattered through the mass, apparently
incipient carbonisation of the peat.
The main land of Noacolly is gradually extending seawards, and has
advanced four miles within twenty- three years: this seems sufficiently
accounted for by the recession of the Megna. The elevation of the
surface of the land is caused by the overwhelming tides and south-west
hurricanes in May and October: these extend thirty miles north and
south of Chittagong, and carry the waters of the Megna and Fenny back
over the land, in a series of tremendous waves, that cover islands of
many hundred acres, and roll three miles on to the main land. On these
occasions, the average earthy deposit of silt, separated by micaceous
sand, is an eighth of an inch for every tide; but in October, 1848,
these tides covered Sundeep island, deposited six inches on its level
surface, and filled ditches several feet deep. These deposits become
baked by a tropical sun, and resist to a considerable degree denudation
by rain. Whether any further rise is caused by elevation from below is
doubtful; there is no direct evidence of it, though slight earthquakes
annually occur; and even when they have not been felt, the water of
tanks has been seen to oscillate for three-quarters of an hour without
intermission, from no discernible cause.[386]
[386] The natives are familiar with this phenomenon, of which Dr.
Baker remembers two instances, one in the cold season of 1834–5, the
other in that of 1830–1. The earthquakes do not affect any particular
month, nor are they accompanied by any meteorological phenomena.
Noacolly is considered a healthy spot, which is not the case with the
Sunderbund stations west of the Megna. The climate is uniformly hot,
but the thermometer never rises above 90°, nor sinks below 45°; at this
temperature hoar-frost will form on straw, and ice on water placed in
porous pans, indicating a powerful radiation.[387]
[387] The winds are north-west and north in the cold season (from
November to March), drawing round to west in the afternoons.
North-west winds and heavy hailstorms are frequent from March to May,
when violent gales set in from the southward. The rains commence in
June, with easterly and southerly winds, and the temperature from 82°
to 84°; May and October are the hottest months. The rains cease in the
end of October (on the 8th of November in 1849, and 12th of November
in 1850, the latest epoch ever remembered): there is no land or sea
breeze along any part of the coast. During our stay we found the mean
temperature for twelve observations to be precisely that of Calcutta,
but the humidity was more, and the pressure 0·040 lower.
We left Noacolly on the 19th for Chittagong; the state of the tide
obliging us to go on board in the night. The distance is only 100
miles, but the passage is considered dangerous at this time (during the
spring-tides) and we were therefore provided with a large vessel and an
experienced crew. The great object in this navigation is to keep afloat
and to make progress towards the top of the tide and during its flood,
and to ground during the ebb in creeks where the bore (tidal wave) is
not violent; for where the channels are broad and open, the height and
force of this wave rolls the largest coasting craft over and swamps
them.
Our boatmen pushed out at 3 in the morning, and brought up at 5, in a
narrow muddy creek on the island of Sidhee. The waters retired along
channels scooped several fathoms deep in black mud, leaving our vessel
aground six or seven feet below the top of the bank, and soon
afterwards there was no water to be seen; as far as the eye could
reach, all was a glistening oozy mud, except the bleak level surfaces
of the islands, on which neither shrub nor tree grew. Soon after 2 p.m.
a white line was seen on the low black horizon, which was the
tide-wave, advancing at the rate of five miles an hour, with a hollow
roar; it bore back the mud that was gradually slipping along the gentle
slope, and we were afloat an hour after: at night we grounded again,
opposite the mouth of the Fenny.
By moonlight the scene was oppressively solemn: on all sides the
gurgling waters kept up a peculiar sound that filled the air with
sullen murmurs; the moonbeams slept upon the slimy surface of the mud,
and made the dismal landscape more ghastly still. Silence followed the
ebb, broken occasionally by the wild whistle of a bird like the curlew,
of which a few wheeled through the air: till the harsh roar of the bore
was heard, to which the sailors seemed to waken by instinct. The waters
then closed in on every side, and the far end of the reflected moonbeam
was broken into flashing light, that approached and soon danced beside
the boat.
We much regretted not being able to obtain any more accurate data than
I have given, as to the height of the tide at the mouth of the Fenny;
but where the ebb sometimes retires twenty miles from high-water mark,
it is obviously impossible to plant any tide-gauge.
On the 21st we were ashore at daylight on the Chittagong coast far
north of the station, and were greeted by the sight of hills on the
horizon: we were lying fully twenty feet below high-water mark, and the
tide was out for several miles to the westward. The bank was covered
with flocks of white geese feeding on short grass, upon what appeared
to be detached islets on the surface of the mud. These islets, which
are often an acre in extent, are composed of stratified mud; they have
perpendicular sides several feet high, and convex surfaces, owing to
the tide washing away the earth from under their sides; and they were
further slipping seawards, along the gently sloping mud-beach. Few or
no shells or seaweed were to be seen, nor is it possible to imagine a
more lifeless sea than these muddy coasts present.
We were three days and nights on this short voyage, without losing
sight of mud or land. I observed the barometer whenever the boat was on
the shore, and found the mean of six readings (all reduced to the same
level) to be identical with that at Calcutta. These being all taken at
elevations lower than that of the Calcutta observatory, show either a
diminished atmospheric pressure, or that the mean level of high-water
is not the same on the east and west coasts of the Bay of Bengal: this
is quite possible, considering the widely different direction of the
tides and currents on each, and that the waters may be banked up, as it
were, in the narrow channels of the western Sunderbunds. The
temperature of the air was the same as at Calcutta, but the atmosphere
was damper. The water was always a degree warmer than the air.
We arrived at Chittagong on the 23rd of December, and became the guests
of Mr. Sconce, Judge of the district, and of Mr. Lautour; to both of
whom we were greatly indebted for their hospitality and generous
assistance in every way.
Chittagong is a large town of Mahometans and Mugs, a Birmese tribe who
inhabit many parts of the Malay peninsula, and the coast to the
northward of it. The town stands on the north shore of an extensive
delta, formed by rivers from the lofty mountains separating this
district from Birma. These mountains are fine objects on the horizon,
rising 4000 to 8000 feet; they are forest-clad, and inhabited by
turbulent races, who are coterminous with the Cookies of the Cachar and
Tipperah forests; if indeed they be not the same people. The mountains
abound with the splendid timber-trees of the Cachar forests, but like
these are said to want teak, Sal, and Sissoo; they have, besides many
others,, magnificent Gurjun trees (_Dipterocarpi_), the monarchs of the
forests of these coasts.
The natives of Chittagong are excellent shipbuilders and active
traders, and export much rice and timber to Madras and Calcutta. The
town is large and beautifully situated, interspersed with trees and
tanks; the hills resemble those of Silhet, and are covered with a
similar vegetation: on these the European houses are built. The climate
is very healthy, which is not remarkable, considering how closely it
approximates in character to that of Silhet and other places in Eastern
Bengal, but very extraordinary, if it be compared with Arracan, only
200 miles further south, which is extremely unhealthy. The prominent
difference between the physical features of Chittagong and Arracan, is
the presence of mangrove swamps at the latter place, for which the
water is too fresh at the former.
The hills about the station are not more than 150 or 200 feet high, and
are formed of stratified gravel, sand, and clay, that often becomes
nodular, and is interstratified with slag-like iron clay. Fossil wood
is found; and some of the old buildings about Chittagong contain
nummulitic limestone, probably imported from Silhet or the peninsula of
India, with which countries there is no such trade now. The views are
beautiful, of the blue mountains forty to fifty miles distant, and the
many-armed river, covered with sails, winding amongst groves of
cocoa-nuts, Areca palm, and yellow rice fields. Good European houses
surmount all the eminences, surrounded by trees of _Acacia_ and
_Cæsalpinia._ In the hollows are native huts amidst vegetation of every
hue, glossy green _Garciniæ_ and figs, broad plantains, feathery
_Cassia_ and Acacias, dark _Mesua_, red-purple _Terminalia,_ leafless
scarlet-flowered _Bombax,_ and grey _Casuarina._[388] Seaward the tide
leaves immense flats, called churs, which stretch for many miles on
either side the offing.
[388] This, which is almost exclusively an Australian genus, is not
indigenous at Chittagong: to it belongs an extra-Australian species
common in the Malay islands, and found wild as far north as Arracan.
We accompanied Mr. Sconce to a bungalow which he has built at the
telegraph station at the south head of the harbour: its situation, on a
hill 100 feet above the sea, is exposed, and at this season the
sea-breeze was invigorating, and even cold, as it blew through the
mat-walls of the bungalow.[389] To the south, undulating dunes stretch
along the coast, covered with low bushes, of which a red-flowered
_Melastoma_ is the most prevalent,[390] and is considered a species of
_Rhododendron_ by many of the residents! The flats along the beach are
several miles broad, intersected with tidal creeks, and covered with
short grass, while below high-water mark all is mud, coated with green
_Conferva._ There are no leafy seaweeds or mangroves, nor any seaside
shrub but _Dilivaria ilicifolia._ Animal life is extremely rare; and a
_Cardium_-like shell and small crab are found sparingly.
[389] The mean temperature of the two days (29th and 30th) we spent at
this bungalow was 66·5°, that of Calcutta being 67·6°; the air was
damp, and the barometer 0·144 lower at the flagstaff hill, but it fell
and rose with the Calcutta instrument.
[390] _Melastoma,_ jasmine, _Calamus, Ægle Marmelos, Adelia,
Memecylon, Ixora, Limostoma, Congea,_ climbing _Cœsalpinia,_ and many
other plants; and along their bases large trees of _Amoora, Gaurea,_
figs, _Mesua,_ and _Micromelon._
Coffee has been cultivated at Chittagong with great success; it is said
to have been introduced by Sir W. Jones, and Mr. Sconce has a small
plantation, from which his table is well supplied. Both Assam and
Chinese teas flourish, but Chinamen are wanted to cure the leaves.
Black pepper succeeds admirably, as do cinnamon, arrowroot, and ginger.
Early in January we accompanied Mr. Lautour on an excursion to the
north, following a valley separated from the coast by a range of wooded
hills, 1000 feet high. For several marches the bottom of this valley
was broad, flat, and full of villages. At Sidhee, about twenty-five
miles from Chittagong, it contracts, and spurs from the hills on either
flank project into the middle: they are 200 to 300 feet high, formed of
red clay, and covered with brushwood. At Kajee-ke-hath, the most
northern point we reached, we were quite amongst these hills, and in an
extremely picturesque country, intersected by long winding flat
valleys, that join one another: some are full of copsewood, while
others present the most beautiful park-like scenery, and a third class
expand into grassy marshes or lake-beds, with wooded islets rising out
of them. The hillsides are clothed with low jungle, above which tower
magnificent Gurjun trees (wood-oil). The whole contour of this country
is that of a low bay, whose coast is raised above the sea, and over
which a high tide once swept for ages.
The elevation of Hazari-ke-hath is not 100 feet above the level of the
sea. It is about ten miles west of the mouth of the Fenny, from which
it is separated by hills 1000 feet high; its river falls into that at
Chittagong, thirty miles south. Large myrtaceous trees (_Eugenia_) are
common, and show a tendency to the Malayan flora, which is further
demonstrated by the abundance of Gurjun (_Dipterocarpus turbinatus_).
This is the most superb tree we met with in the Indian forests: we saw
several species, but this is the only common one here; it is
conspicuous for its gigantic size, and for the straightness and
graceful form of its tall unbranched pale grey trunk, and small
symmetrical crown: many individuals were upwards of 200 feet high, and
fifteen in girth. Its leaves are broad, glossy, and beautiful; the
flowers (then falling) are not conspicuous; the wood is hard,
close-grained, and durable, and a fragrant oil exudes from the trunk,
which is extremely valuable as pitch and varnish, etc., besides being a
good medicine. The natives procure it by cutting transverse holes in
the trunk, pointing downwards, and lighting fires in them, which causes
the oil to flow.[391]
[391] The other trees of these dry forests are many oaks, _Henslowia,
Gordonia, Engelhardtia, Duabanga, Adelia, Byttneria, Bradleia,_ and
large trees of _Pongamia,_ whose seeds yield a useful oil.
[Illustration: Gurjun tree]
On the 8th of January we experienced a sharp earthquake, preceded by a
dull thumping sound; it lasted about twenty seconds, and seemed to come
up from the southward; the water of a tank by which we were seated was
smartly agitated. The same shock was felt at Mymensing and at Dacca,
110 miles north-west of this.[392]
[392] Earthquakes are extremely common, and sometimes violent, at
Chittagong, and doubtless belong to the volcanic forces of the Malayan
peninsula.
We crossed the dividing ridge of the littoral range on the 9th, and
descended to Seetakoond bungalow, on the high road from Chittagong to
Comilla. The forests at the foot of the range were very extensive, and
swarmed with large red ants that proved very irritating: they build
immense pendulous nests of dead and living leaves at the ends of the
branches of trees, and mat them with a white web. Tigers, leopards,
wild dogs, and boars, are numerous; as are snipes, pheasants, peacocks,
and jungle-fowl, the latter waking the morn with their shrill crows;
and in strange association with them, common English woodcock, is
occasionally found.
The trees are of little value, except the Gurjun, and “Kistooma,” a
species of _Bradleia,_ which was stacked extensively, being used for
building purposes. The papaw[393] is abundantly cultivated, and its
great gourd-like fruit is eaten (called “Papita” or “Chinaman”); the
flavour is that of a bad melon, and a white juice exudes from the rind.
The _Hodgsonia heteroclita_ (_Trichosanthes_ of Roxburgh), a
magnificent Cucurbitaceous climber, grows in these forests; it is the
same species as the Sikkim one (see p. 7). The long stem bleeds
copiously when cut, and like almost all woody climbers, is full of
large vessels; the juice does not, however, exude from these great
tubes, which hold air, but from the close woody fibres. A climbing
_Apocyneous_ plant grows in these forests, the milk of which flows in a
continuous stream, resembling caoutchouc (it is probably the _Urceola
elastica,_ which yields Indian-rubber).
[393] The Papaw tree is said to have the curious property of rendering
tough meat tender, when hung under its leaves, or touched with the
juice; this hastening the process of decay. With this fact, well-known
in the West Indies, I never found a person in the East acquainted.
The subject of bleeding is involved in great obscurity, and the
systematic examination of the motions in the juices of tropical
climbers by resident observers, offers a fertile field to the
naturalist. I have often remarked that if a climbing stem, in which the
circulation is vigorous, be cut across, it bleeds freely from both
ends, and most copiously from the lower, if it be turned downwards; but
that if a truncheon be severed, there will be no flow from either of
its extremities. This is the case with all the Indian watery-juiced
climbers, at whatever season they may be cut. When, however, the
circulation in the plant is feeble, neither end of a simple cut will
bleed much, but if a truncheon be taken from it, both the extremities
will.
The ascent of the hills, which are densely wooded, was along spurs, and
over knolls of clay; the rocks were sandy and slaty (dip north-east
60°. The road was good, but always through bamboo jungle, and it wound
amongst the low spurs, so that there was no defined crest or top of the
pass, which is about 800 feet high. There were no tall palms,
tree-ferns, or plantains, no _Hymenophylla_ or _Lycopodia,_ and
altogether the forest was smaller and poorer in plants than we had
expected. The only palms (except a few rattans) were two kinds of
_Wallichia._
From the summit we obtained a very extensive and singular view. At our
feet was a broad, low, grassy, alluvial plain, intersected by creeks,
bounding a black expanse of mud which (the tide being out) appeared to
stretch almost continuously to Sundeep Island, thirty miles distant;
while beyond, the blue hills of Tipperah rose on the north-west
horizon. The rocks yielded a dry poor soil, on which grew dwarf
_Phœnix_ and cycas-palm (_Cycas circinalis_ or _pectinata_).
Descending, we rode several miles along an excellent road, that runs to
Tipperah, and stopped at the bungalow of Seetakoond, twenty-five miles
north of Chittagong. The west flank of the range which we had crossed
is much steeper than the east, often precipitous, and presents the
appearance of a sea-worn cliff towards the Bay of Bengal. Near
Seetakoond (which is on the plain) a hill on the range, bearing the
same name, rises 1,136 feet high, and being damper and more luxuriantly
wooded, we were anxious to explore it, and therefore spent some days at
the bungalow. Fields of poppy and sun (_Crotalaria juncea_), formed
most beautiful crops; the latter grows from four to six feet high, and
bears masses of laburnum-like flowers, while the poppy fields resembled
a carpet of dark-green velvet, sprinkled with white stars; or, as I
have elsewhere remarked, a green lake studded with water-lilies.
[Illustration: Seetakund Hill]
The road to the top of Seetakoond leads along a most beautiful valley,
and then winds up a cliff that is in many places almost precipitous,
the ascent being partly by steps cut in the rock, of which there are
560. The mountain is very sacred, and there is a large Brahmin temple
on its flank; and near the base a perpetual flame bursts out of the
rock. This we were anxious to examine, and were extremely disappointed
to find it a small vertical hole in a slaty rock, with a lateral one
below for a draught; and that it is daily supplied by pious pilgrims
and Brahmins with such enormous quantities of ghee (liquid butter),
that it is to all intents and purposes an artificial lamp; no trace of
natural phenomena being discoverable.
On the dry but wooded west face of the mountain, grows _Falconeria,_ a
curious Euphorbiaceous tree, with an acrid milky juice that affects the
eyes when the wood is cut. Beautiful _Cycas_ palms are also common,
with _Terminalia, Bignonia, Sterculia,_ dwarf _Phœnix_ palm, and Gurjun
trees. The east slope of the mountain is damper, and much more densely
wooded; we there found two wild species of nutmeg trees, whose wood is
full of a brown acrid oil, seven palms, tree-ferns, and many other
kinds of ferns, several kinds of oak, _Dracæna,_ and figs. The top is
1,136 feet above the sea, and commands an extensive view to all points
of the compass; but the forests, in which the ashy bark of the Gurjun
trees is conspicuous, and the beautiful valley on the west, are the
only attractive features.
The weather on the east side of the range differs at this season
remarkably from that on the west, where the vicinity of the sea keeps
the atmosphere more humid and warm, and at the same time prevents the
formation of the dense fogs that hang over the valleys to the eastward
every morning at sunrise. We found the mean temperature at the
bungalow, from January 9th till the 13th, to be 70·2°.
We embarked again at Chittagong on the 16th of January, at 10 p.m., for
Calcutta, in a very large vessel, rowed by twelve men: we made
wretchedly slow progress, for the reasons mentioned above (p. 343),
being for four days within sight of Chittagong! On the 20th we only
reached Sidhee, and thence made a stretch to Hattiah, an island which
may be said to be moving bodily to the westward, the Megna annually
cutting many acres from the east side; and the tide-wave depositing mud
on the west. The surface is flat, and raised four feet above mean
high-water level; the tide rises about 14 feet up the bank, and then
retires for miles; the total rise and fall is, however, much less here
than in the Fenny, higher up the gulf. The turf is composed of
_Cynodon_ and a _Fimbristylis_; and the earth being impregnated with
salt, supports different kinds of _Chenopodium._ Two kinds of tamarisk,
and a thorny _Cassia_ and _Exœcaria,_ are the only shrubs on the
eastern islands; on the central ones a few dwarf mangroves appear, with
the holly-leaved _Dilivaria,_ dwarf screw-pine (_Pandanus_), a shrub of
_Compositæ,_ and a curious fern, a variety of _Aristichum aureum._
Towards the northern end of Hattiah, Talipot, cocoa-nut and date-palms
appear.
On the 22nd we entered the Sunderbunds, rowing amongst narrow channels,
where the tide rises but a few feet. The banks were covered with a
luxuriant vegetation, chiefly of small trees, above which rose stately
palms. On the 25th, we were overtaken by a steamer from Assam, a novel
sight to us, and a very strange one in these creeks, which in some
places seemed hardly broad enough for it to pass through. We jumped on
board in haste, leaving our boat and luggage to follow us. She had left
Dacca two days before, and this being the dry season, the route to
Calcutta, which is but sixty miles in a straight line, involved a
détour of three hundred.
From the masts of the steamer we obtained an excellent _coup-d’œil_ of
the Sunderbunds; its swamps clothed with verdure, and intersected by
innumerable inosculating channels, with banks a foot or so high. The
amount of tide, which never exceeds ten feet, diminishes in proceeding
westwards into the heart of these swamps, and the epoch, direction, and
duration of the ebb and flow vary so much in every canal, that at
times, after stemming a powerful current, we found ourselves, without
materially changing our course, suddenly swept along with a favouring
stream. This is owing to the complex ramifications of the creeks, the
flow of whose waters is materially influenced by the most trifling
accidents of direction.
Receding from the Megna, the water became saltier, and _Nipa fruticans_
appeared, throwing up pale yellow-green tufts of feathery leaves, from
a short thick creeping stem, and bearing at the base of the leaves its
great head of nuts, of which millions were floating on the waters, and
vegetating in the mud. Marks of tigers were very frequent, and the
footprints of deer, wild boars, and enormous crocodiles: these reptiles
were extremely common, and glided down the mud banks on the approach of
the steamer, leaving between the footmarks a deep groove in the mud
made by their tail. The _Phœnix paludosa,_ a dwarf slender-stemmed
date-palm, from six to eight feet high, is the all-prevalent feature,
covering the whole landscape with a carpet of feathery fronds of the
liveliest green. The species is eminently gregarious, more so than any
other Indian palm, and presents so dense a mass of foliage, that when
seen from above, the stems are wholly hidden.[394]
[394] _Sonneratia, Heritiera littoralis,_ and _Careya,_ form small
gnarled trees on the banks, with deep shining green-leaved species of
_Carallia Rhizophora,_ and other Mangroves. Occasionally the gigantic
reed-mace (_Typha elephantina_) is seen, and tufts of tall reeds
(_Arundo_).
The water is very turbid, and only ten to twenty feet deep, which, we
were assured by the captain, was not increased during the rains: it is
loaded with vegetable matter, but the banks are always muddy, and we
never saw any peat. Dense fogs prevented our progress in the morning,
and we always anchored at dusk. We did not see a village or house in
the heart of the Sunderbunds (though such do occur), but we saw canoes,
with fishermen, who use the tame otter in fishing; and the banks were
covered with piles of firewood, stacked for the Calcutta market. As we
approached the Hoogly, the water became very salt and clear; the Nipa
fruits were still most abundant, floating out to sea, but no more of
the plant itself was seen. As the channels became broader, sand-flats
appeared, with old salt factories, and clumps of planted _Casuarina._
On the 28th of January we passed Saugor island, and entered the Hoogly,
steamed past Diamond Harbour, and landed at the Botanic Garden Ghat,
where we received a hearty welcome from Dr. Falconer. Ten days later we
bade farewell to India, reaching England on the 25th of March, 1851.
APPENDIX
A.
METEOROLOGICAL OBSERVATIONS IN BEHAR, AND IN THE VALLEYS OF THE SOANE
AND GANGES.
Most of the instruments which I employed were constructed by Mr.
Newman, and with considerable care: they were in general accurate, and
always extremely well guarded, and put up in the most portable form,
and that least likely to incur damage; they were further frequently
carefully compared by myself. These are points to which too little
attention is paid by makers and by travellers in selecting instruments
and their cases. This remark applies particularly to portable
barometers, of which I had five at various times. Although there are
obvious defects in the system of adjustment, and in the method of
obtaining the temperature of the mercury, I found that these
instruments invariably worked well, and were less liable to derangement
and fracture than any I ever used; the best proof I can give of this is
that I preserved three uninjured during nearly all my excursions, left
two in India, and brought a third home myself that had accompanied me
almost throughout my journey.
In very dry climates these and all other barometers are apt to leak,
from the contraction of the box-wood plug through which the tube passes
into the cistern. This must, in portable barometers, in very dry
weather, be kept moist with a sponge. A small iron bottle of pure
mercury to supply leakage should be supplied with every barometer, as
also a turnscrew. The vernier plate and scale should be screwed, not
soldered on the metal sheath, as if an escape occurs in the
barometer-case the solder is acted upon at once. A table of corrections
for capacity and capillarity should accompany every instrument, and
simple directions, etc., in cases of trifling derangement, and
alteration of neutral point.
The observations for temperature were taken with every precaution to
avoid radiation, and the thermometers were constantly compared with a
standard, and the errors allowed for. The maximum thermometer with a
steel index, I found to be extremely liable to derangement and very
difficult to re-adjust. Negretti’s maximum thermometer was not known to
me during my journey. The spirit minimum thermometers again, are easily
set to rights when out of order, but in every one (of six or seven)
which I took to India, by several makers, the zero point receded, the
error in some increasing annually, even to –6° in two years. This seems
due to a vaporisation of the spirit within the tube. I have seen a
thermometer of this description in India, of which the spirit seemed to
have retired wholly into the bulb, and which I was assured had never
been injured. In wet-bulb observations, distilled water or rain, or
snow water was used, but I never found the result to differ from that
obtained by any running fresh water, except such as was polluted to the
taste and eye.
The hours of observation selected were at first sunrise, 9 a.m., 3
p.m., sunset, and 9 p.m., according to the instructions issued to the
Antarctic expedition by the Royal Society. In Sikkim, however, I
generally adopted the hours appointed at the Surveyor General’s office,
Calcutta; viz., sunrise, 9h. 50m. a.m., noon, 2h. 40m. p.m., 4 p.m.,
and sunset, to which I added a 10 p.m. observation, besides many at
intermediate hours as often as possible. Of these the 9h. 50m. a.m. and
4 p.m. have been experimentally proved to be those of the maximum and
minimum of atmospheric pressure at the level of the sea in India, and I
did not find any great or marked deviation from this at any height to
which I attained, though at 15,000 or 16,000 feet the morning maximum
may occur rather earlier.
The observations for nocturnal (terrestrial) radiation were made by
freely suspending thermometers with naked bulbs, or by laying them on
white cotton, wool, or flannel; also by means of a thermometer placed
in the focus of a silvered parabolic reflector. I did not find that the
reflector possessed any decided advantage over the white cotton: the
means of a number of observations taken by each approximated closely,
but the difference between individual observations often amounted to
2°.
Observations again indicative of the radiation from grass, whether
dewed or dry, are not strictly comparable; not only does the power of
radiation vary with the species, but much more with the luxuriance and
length of the blades, with the situation, whether on a plane surface or
raised, and with the subjacent soil. Of the great effect of the soil I
had frequent instances; similar tufts of the same species of grass
radiating more powerfully on the dry sandy bed of the Soane, than on
the alluvium on its banks; the exposure being equal in both instances.
Experiments for the surface-temperature of the soil itself, are least
satisfactory of any:—adjoining localities being no less affected by the
nature, than by the state of disintegration of the surface, and by the
amount of vegetation in proximity to the instrument.
The power of the sun’s rays in India is so considerable, and protracted
through so long a period of the day, that I did not find the
temperature of springs, or of running water, even of large deep rivers,
so constant as was to be expected.
The temperature of the earth was taken by sinking a brass tube a yard
long in the soil.
A thermometer with the bulb blackened affords the only means the
traveller can generally compass, of measuring the power of the sun’s
rays. It should be screened or put in a blackened box, or laid on black
wool.
A good Photometer being still a desideratum, I had recourse to the old
wedge of coloured glass, of an uniform neutral tint, the distance
between whose extremes, or between transparency and total opacity, was
one foot. A moveable arm carrying a brass plate with a slit and a
vernier, enables the observer to read off at the vanishing point of the
sun’s limb, to one five-hundredth of an inch. I generally took the mean
of five readings as one, and the mean of five of these again I regarded
as one observation; but I place little dependence upon the results. The
causes of error are quite obvious. As far as the effects of the sun’s
light on vegetation are concerned, I am inclined to think that it is of
more importance to register the number of hours or rather of parts of
each hour, that the sun shines, and its clearness during the time. To
secure valuable results this should be done repeatedly, and the
strength of the rays by the black-bulb thermometer registered at each
hour. The few actinometer observations will be found in another part of
the Appendix.
The dew-point has been calculated from the wet-bulb, by Dr. Apjohn’s
formula, or, where the depression of the barometer is considerable, by
that as modified by Colonel Boileau.[395] The saturation-point was
obtained by dividing the tension at the dew-point by that at the
ordinary temperature, and the weight of vapour, by Daniell’s formula.
[395] Journal of Asiatic Society, No. 147 (1844), p.135.
The following summary of meteorological observations is alluded to at
vol. i., p. 15.
I.—_Table-land of Birbhoom and Behar, from Taldanga to Dunwah. Average
elevation 1,135 feet._
It is evident from these observations, that compared with Calcutta, the
dryness of the atmosphere is the most remarkable feature of this
table-land, the temperature not being high; and to this, combined with
the sterility of the soil over a great part of the surface, must be
attributed the want of a vigorous vegetation. Though so favourably
exposed to the influence of nocturnal radiation, the amount of the
latter is small. The maximum depression of a thermometer laid on grass
never exceeded 10°, and averaged 7°; whereas the average depression of
the dew-point at the same hour amounted to 25° in the morning. Of
course no dew was deposited even in the clearest star-light night.
February 1848 Hour Sunrise 9 a.m. 3 p.m. 9 p.m.
TEMPERATURE
Mean
Max.
Min.
Range 56·6
65·2
46·3
18·9 70·1
77·0
61·2
15·8 75·5
81·7
65·2
16·5 61·7
66·2
55·5
10·7 WET-BULB
Mean
Max. Depression
Min. Depression 48·2
12·5
6·0 53·7
19·3
14·3 55·3
22·5
16·7 49·3
20·5
9·0 Elasticity of Vapour ·276 ·264 ·248 ·248 DEW-POINT
Mean
Max.
Min.
Max. Depression
Min. Depression 39·5
52·0
23·3
31·7
10·4 37·9
52·7
24·5
39·2
24·3 36·0
46·8
24·3
48·4
34·9 36·1
50·0
[396]9·1
56·9
16·2 Weight of Vapour in cubic feet 3·088 2·875 2·674 2·745
SATURATION
Mean
Max.
Min. ·550
·680
·330 ·330
·450
·260 ·260
·320
·190 ·410
·590
·140 Number of observations 7 7 7 10
Extreme variations of temperature 35·4° Extreme variations of
relative humidity ·540 Extreme diff. solar and nocturnal radiation
96·5°
[396] Taken during a violent N.W. dust-storm.
SOLAR RADIATION
MORNING Hour Th. Black
Bulb Diff. Phot. 9.30 a.m.
10 a.m.
10 a.m.
9 a.m.
9 a.m.
9 a.m. 77·0
69·5
77·0
63·5
61·2
67·0 130
124
137
94
106
114 53·0
54·5
60·0
30·5
44·8
47·0 --
10·320
--
10·230
--
10·350 Mean 69·2 117·5 48·1 10·300
AFTERNOON Hour Th. Black
Bulb Diff. Phot. 3.30 p.m.
3 p.m.
3 p.m.
3.30 p.m.
3 p.m. 81·7
80·5
81·5
72·7
72·5 109
120
127
105
110 27·3
39·5
45·5
32·3
37·5 --
10·320
10·330
10·230
10·390 Mean 77·8 114·2 68·4 10·318
NOCTURNAL RADIATION
SUNRISE Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 51·1
4·0
9·0
6 48·3
2·5
3·7
3 46·6
6·2
9·0
5
NINE P.M. Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 56·4
5·3
7·5
7 53·8
4·9
5·5
6 54·4
7·2
10·0
7
On one occasion, and that at night, the dew-point was as low as 11·5°,
with a temperature of 66°, a depression rarely equalled at so low a
temperature: this phenomenon was transient, and caused by the passage
of a current of air loaded with dust, whose particles possibly absorbed
the atmospheric humidity. From a comparison of the night and morning
observations of thermometers laid on grass, the earth, and freely
exposed, it appears that the grass parts with its heat much more
rapidly than the earth, but that still the effect of radiation is
slight, lowering its temperature but 2° below that of the freely
exposed thermometer.
As compared with the climate of Calcutta, these hills present a
remarkable contrast, considering their proximity in position and
moderate elevation.
The difference of temperature between Calcutta and Birbhoom, deduced
from the sunrise, morning and afternoon observations, amounts to 4°,
which, if the mean height of the hills where crossed by the road, be
called 1,135 feet, will be equal to a fall of one degree for every 288
feet.
In the dampness of its atmosphere, Calcutta contrasts very remarkably
with these hills; the dew-point on the Hoogly averaging 51·3°, and on
these hills 38°, the corresponding saturation-points being 0·559 and
0·380.
The difference between sunrise, forenoon and afternoon dew-points at
Calcutta and on the hills, is 13·6° at each observation; but the
atmosphere at Calcutta is relatively drier in the afternoon than that
of the hills; the difference between the Calcutta sunrise and afternoon
saturation-point being 0·449, and that between the hill sunrise and
afternoon, 0·190. The march of the dew-point is thus the same in both
instances, but owing to the much higher temperature of Calcutta, and
the greatly increased tension of the vapour there, the relative
humidity varies greatly during the day.
In other words, the atmosphere of Calcutta is loaded with moisture in
the early morning of this season, and is relatively dry in the
afternoon: in the hills again, it is scarcely more humid at sunrise
than at 3 p.m. That this dryness of the hills is partly due to
elevation, appears from the disproportionately moister state of the
atmosphere below the Dunwah pass.
II.—_Abstract of the Meteorological observationsctaken in the Soane
Valley
(mean elevation 422 feet)._
The difference in mean temperature (partly owing to the sun’s more
northerly declination) amounts to 2·5° of increase in the Soane valley,
above that of the hills. The range of the thermometer from day to day
was considerably greater on the hills (though fewer observations were
there recorded): it amounted to 17·2° on the hills, and only 12·8° in
the valley. The range from the maximum to the minimum of each day
amounts to the same in both, above 20°. The extreme variations in
temperature too coincide within 1·4°.
The hygrometric state of the atmosphere of the valley differs most
decidedly from that of the hills. In the valley dew is constantly
formed, which is owing to the amount of moisture in the air, for
nocturnal radiation is more powerful on the hills. The sunrise and 9
p.m. observations in the valley, give a mean depression of the
dew-point below the air of 12·3°, and those at the upper level of
21·2°, with no dew on the hills and a copious deposit in the valley.
The corresponding state of the atmosphere as to saturation is 0·480 on
the hills and 0·626 in the valley.
The vegetation of the Soane valley is exposed to a less extreme
temperature than that of the hills; the difference between solar and
nocturnal radiation amounting here only to 80·5°, and on the hills to
96·5°. There is no material difference in the power of the sun’s rays
at the upper and lower levels, as expressed by the blackbulb
thermometer, the average rise of which above one placed in the shade,
amounted to 48° in both cases, and the maximum occurred about 11 a.m.
The decrease of the power of the sun’s rays in the afternoon is much
the most rapid in the valley, coinciding with a greater reduction of
the elasticity of vapour and of humidity in the atmosphere.
The photometer observations show a greater degree of sun’s light on the
hills than below, but there is not at either station a decided relation
between the indications of this instrument and the black-bulb
thermometer. From observations taken elsewhere, I am inclined to
attribute the excess of solar light on the hills to their elevation;
for at a far greater elevation I have met with much stronger solar
light, in a very damp atmosphere, than I ever experienced in the drier
plains of India. In a damp climate the greatest intensity may be
expected in the forenoon, when the vapour is diffused near the earth’s
surface; in the afternoon the lower strata of atmosphere are drier, but
the vapour is condensed into clouds aloft which more effectually
obstruct the sun’s rays. On the Birbhoom and Behar hills, where the
amount of vapour is so small that the afternoon is but little drier
than the forenoon, there is little difference between the solar light
at each time. In the Soane valley again, where a great deal of humidity
is removed from the earth’s surface and suspended aloft, the
obstruction of the sun’s light is very marked.
DUNWAH TO SOANE RIVER, AND UP SOANE TO TURA
February 10–19th Hour Sunrise 9 a.m. 3 p.m. 9 p.m.
TEMPERATURE
Mean
Max.
Min.
Range 57·6
62·0
53·5
8·5 74·0
81·0
63·5
17·5 77·6
87·5
71·0
16·5 64·5
68·7
60·0
8·7 WET-BULB
Mean
Max. Depression
Min. Depression 51·7
8·5
3·8 59·5
18·5
4·0 59·9
26·0
6·8 55·5
12·5
2·5 Elasticity of Vapour 0·352 0·382 0·357 0·370 DEW-POINT
Mean
Max.
Min.
Max. Depression
Min. Depression 46·1
53·6
40·6
16·9
7·0 48·5
56·7
38·0
33·5
6·8 46·4
60·0
36·0
44·2
11·0 47·5
55·6
41·0
24·1
4·4 Weight of Vapour in cubic
feet 3·930 4·066 3·658 4·014 SATURATION
Mean
Max.
Min. ·680
·787
·566 ·460
·818
·338 ·352
·703
·237 ·572
·860
·452 Number of observations 10 8 9 10
Extreme variations of temperature 34·0° Extreme variations of
relative humidity ·623 Extreme diff. solar and nocturnal radiation
80·5°
NOCTURNAL RADIATION
SUNRISE Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 53·2
4·5
8·5
9 54·0
3·7
9·0
9 51·5
6·2
7·5
8
NINE P.M. Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 59·9
4·6
11·5
10 60·7
3·8
10·5
10 56·4
8·1
13·5
10
SOLAR RADIATION
MORNING Time Th. Black
Bulb Diff. Phot. 9 a.m.
11 a.m.
10.30 a.m.
10 a.m.
10 a.m.
10.30 a.m. 70·0
81·0
71·5
72·0
80·0
78·0 125
119
126
117
122
128 55·0
38·0
54·5
45·0
42·0
50·0 10·300
10·230
10·300
10·220
--
-- Mean 75·4 122·8 47·4 10·262
AFTERNOON Time Th. Black
Bulb Diff. Phot. 4 p.m.
3 p.m.
3 p.m.
3 p.m. 76·5
80·0
76·0
87·5 90
105
102
126 13·5
25·0
26·0
38·5 --
10·210
10·170
-- Mean 80·0 105·7 25·7 10·190
NOCTURNAL RADIATION FROM PLANTS
SUNRISE NINE P.M. Air
temperature 59·5 55·0 67·5 67·0 64·3
Calotropis -- 49·5 -- -- 58·5 Difference --
5·5 -- -- 5·83
Argemone 57·0 47·0 53·0 56·0 57·0 Difference
2·5 8·0 14·0 11·0 7·3
III.—_VALLEY OF SOANE RIVER, TURA TO SULKUN
(Mean elev. 517 feet)_
February 20th to March 3rd Hour Sunrise 9 a.m. 3
p.m. 9 p.m. TEMPERATURE
Mean
Max.
Min.
Range 56·8
70·0
50·0
20·0 82·0
89·0
69·0
20·0 88·6
94·7
81·5
13·2 68·0
74·0
61·0
13·0 WET-BULB
Mean
Max. Depression
Min. Depression 52·5
10·0
1·5 61·2
24·3
12·0 62·4
30·2
14·5 56·8
15·0
6·0 Elasticity of Vapour 0·380 0·385 0·289 0·369
DEW-POINT
Mean
Max.
Min.
Max. Depression
Min. Depression 48·3
53·1
41·1
17·3
5·4 48·7
60·2
40·3
45·2
22·0 40·8
50·9
32·3
57·2
25·1 47·4
51·8
42·6
27·1
10·2 Weight of Vapour in cubic feet 4·240 4·097 2·975 3·933
SATURATION
Mean
Max.
Min. ·754
·831
·570 ·342
·488
·226 ·211
·598
·154 ·511
·703
·415 Number of observations 12 11 11 11
Extreme variation of temperature 44·7° Extreme variation of relative
humidity ·677 Extreme diff. solar and nocturnal radiation 100°
NOCTURNAL RADIATION
SUNRISE Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 51·7
5·1
8·0
9 52·4
3·4
7·0
9 48·8
7·0
11·5
9
NINE P.M. Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 61·2
6·8
10·5
10 64·3
4·6
8·5
9 55·8
11·8
17·0
9
SOLAR RADIATION
MORNING Time Temp. Black
Bulb Diff. Phot. 11.30 a.m.
10.30 a.m.
Noon
Noon
Noon
Noon 85·5
89·0
90·0
85·0
86·0
90·0 129
132
132
130
138
138 44·5
43·0
42·0
45·0
52·0
48·0 --
--
10·140
--
--
-- Mean 87·6 133 45·8 10·140
AFTERNOON Time Temp. Black
Bulb Diff. Phot. 3 p.m.
--
--
--
-- 85·5
92·5
92·0
89·5
93·5 116
128
120
128
144 30·5
35·5
28·0
38·5
50·5 --
--
--
--
-- Mean 90·6 127 36·6 --
NOCTURNAL RADIATION FROM PLANTS
SUNRISE Air
temperature Barley Diff. Calo-
tropis Diff. Arge-
mone Diff. 61·0
57·0
57·0
58·5
57·0
50·0
50·5
56·0 56
46
52
52
52
45
43
-- 5·0
11·0
5·0
6·5
5·0
5·0
7·5
-- 56·5
48·0
--
--
--
45·5
--
-- 4·5
9·0
--
--
--
4·5
--
-- 57·0
50·0
50·0
--
--
--
--
49·0 4·0
7·0
7·0
--
--
--
--
7·0 55·9 49·4 6·4 50·0 6·0 51·5 6·2 NINE P.M. Air
temperature Barley Diff. Calo-
tropis Diff. Arge-
mone Diff. 68·5
70·0
69·0
74·0
62·5
67·5
61·0 --
--
--
--
51·5
67·5
50·0 --
--
--
--
11·0
10·0
11·0 --
65·0
57·0
59·0
--
62·5
-- --
5·0
12·0
15·0
--
5·0
-- 56·0
67·0
57·0
--
--
--
-- 12·5
3·0
12·0
--
--
--
-- 67·5 56·3 10·7 60·9 9·3 60·0 9·2
The upper course of the Soane being in some places confined, and
exposed to furious gusts from the gullies of the Kymore hills, and at
others expanding into a broad and flat valley, presents many
fluctuations of temperature. The mean temperature is much above that of
the lower parts of the same valley (below Tura), the excess amounting
to 5.4°. The nights and mornings are cooler, by 1·2°, the days hotter
by 10°. There were also 10° increase of range during the thirteen days
spent there; and the mean range from day to day was nearly as great as
it was on the hills of Bengal.
There being much exposed rock, and the valley being swept by violent
dust-storms, the atmosphere is drier, the mean saturation point being
·454, whereas in the lower part of the Soane’s course it was ·516.
A remarkable uniformity prevails in the depression of thermometers
exposed to nocturnal radiation, whether laid on the earth, grass, or
freely exposed; both the mean and maximum indication coincide very
nearly with those of the lower Soane valley and of the hills. The
temperature of tufts of green barley laid on the ground is one degree
higher than that of short grass; _Argemone_ and _Calotropis_ leaves
maintain a still warmer temperature; from the previous experiments the
_ Argemone_ appeared to be considerably the cooler, which I was
inclined to attribute to the smoother and more shining surface of its
leaf, but from these there would seem to be no sensible difference
between the radiating powers of the two plants.
IV.—_TABLE-LAND OF KYMORE HILLS
(Mean elev. 979 feet)_
February 20th to March 3rd Hour Sunrise 9 a.m. 3
p.m. 9 p.m. TEMPERATURE
Mean
Max.
Min.
Range 65·3
69·0
57·5
11·5 81·6
83·5
79·5
4·0 88·1
90·0
84·5
5·5 71·1
76·0
68·0
8·0 WET-BULB
Mean
Max. Depression
Min. Depression 57·7
8·0
6·0 65·3
19·0
14·0 63·3
26·5
21·5 60·3
13·0
8·3 Elasticity of Vapour 0·428 0·468 0·324 0·433
DEW-POINT
Mean
Max.
Min.
Max. Depression
Min. Depression 52·0
55·5
45·9
14·1
11·6 54·5
57·9
49·0
33·0
12·9 43·7
47·8
37·9
46·6
42·2 52·3
56·7
46·8
21·9
13·8 Weight of Vapour in cubic feet 4·710 5·000 3·417 4·707
SATURATION
Mean
Max.
Min. ·647
·741
·648 ·421
·479
·344 ·240
·295
·214 ·542
·643
·491 Number of observations 4 3 3 4
Extreme variation of temperature 32·5° Extreme variation of relative
humidity ·527 Extreme diff. solar and nocturnal radiation
110·5°
NOCTURNAL RADIATION
SUNRISE Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 59·5
3·5
3·5
2 56·0
1·5
1·5
1 54·7
8·2
8·5
2
NINE P.M. Exposed
thermometer On earth On grass Temperature
Mean diff. from air
Max. diff. from air
Number of observations 71·5
3·3
7·0
3 62·5
5·5
5·5
1 61·0
8·2
11·0
2
The rapid drying of the lower strata of the atmosphere during the day,
as indicated by the great decrease in the tension of the vapour from 9
a.m. to 3 p.m., is the effect of the great violence of the north-west
winds.
From the few days’ observations taken on the Kymore hills, the
temperature of their flat tops appeared 5° higher than that of the
Soane valley, which is 500 feet below their mean level. I can account
for this anomaly only on the supposition that the thick bed of
alluvium, freely exposed to the sun (not clothed with jungle), absorbs
the sun’s rays and parts with its heat slowly. This is indicated by the
increase of temperature being due to the night and morning
observations, which are 3·1° and 8·5° higher here than below, whilst
the 9 a.m. and 3 p.m. temperatures are half a degree lower.
The variations of temperature too are all much less in amount, as are
those of the state of the atmosphere as to moisture, though the climate
is rather damper.
On the subject of terrestrial radiation the paucity of the observations
precludes my dwelling. Between 9 p.m. and sunrise the following morning
I found the earth to have lost but 6·5° of heat, whereas a mean of nine
observations at the same hours in the valley below indicated a loss of
12°.
Though the mean temperature deduced from the few days I spent on this
part of the Kymore is so much above that of the upper Soane valley,
which it bounds, I do not suppose that the whole hilly range partakes
of this increase. When the alluvium does not cover the rock, as at
Rotas and many other places, especially along the southern and eastern
ridges of the ghats, the nights are considerably cooler than on the
banks of the Soane; and at Rotas itself, which rises almost
perpendicularly from the river, and is exposed to no such radiation of
heat from a heated soil as Shahgunj is, I found the temperature
considerably below that of Akbarpore on the Soane, which however is
much sheltered by an amphitheatre of rocks.
V.—_Mirzapore on the Ganges._
During the few days spent at Mirzapore, I was surprised to find the
temperature of the day cooler by nearly 4° than that of the hills
above, or of the upper part of the Soane valley, while the nights on
the other hand were decidedly warmer. The dew-point was even lower in
proportion, 7·6°, and the climate consequently drier. The following is
an abstract of the observations taken at Mr. Hamilton’s house on the
banks of the Ganges (p. 363).
It is remarkable that nocturnal radiation as registered at sunrise is
much more powerful at Mirzapore than on the more exposed Kymore
plateau; the depression of the thermometer freely exposed being 3°
greater, that laid on bare earth 6°, and that on the grass 1·4°
greater, on the banks of the Ganges.
During my passage down the Ganges the rise of the dew-point was very
steady, the maximum occurring at the lowest point on the river,
Bhaugulpore, which, as compared with Mirzapore, showed an increase of
8° in temperature, and of 30·6° in the rise of the dew-point. The
saturation-point at Mirzakore was ·331, and at the corresponding hours
at Bhaugulpore ·742.
MIRZAPORE (Mean elev. 362 feet)
March 9th to 13th, 1848 Hour Sunrise 9 a.m. 3 p.m. 9
p.m. TEMPERATURE
Mean
Max.
Min.
Range 61·1
63·0
58·0
5·0 76·1
83·0
71·0
12·0 86·0
--
--
-- 76·0
--
--
-- WET-BULB
Mean
Max. Depression
Min. Depression 48·8
51·5
47·0 58·5
56·5
51·7 61·7
24·3
-- 63·5
12·5
-- Elasticity of Vapour ·236 ·302 ·295 ·480 DEW-POINT
Mean
Max.
Min.
Max. Depression
Min. Depression 34·3
39·7
29·7
32·8
23·8 41·9
--
--
52·3
15·7 41·3
--
--
44·7
-- 55·2
--
--
20·8
-- Weight of Vapour in cubic feet 2·574 3·271 3·089 5·127
SATURATION
Mean
Max.
Min. ·405
·450
·327 ·324
·603
·176 ·264
--
-- ·511
--
-- Number of observations 3 3 1 1
Air in
shade
Sunrise Exposed
Therm. Diff. Exposed
on earth Diff. Exposed
on grass Diff. 60·0
62·5
63·0
58·0 55·0
54·5
55·5
53·0 5·0
8·0
7·5
5·0 --
56·0
50·5
54·0 --
6·5
12·5
4·0 52·0
52·5
50·5
50·0 8·0
10·0
12·5
8·0 60·9 54·6 6·4 53·5 7·7 51·3 9·6
B.
ON THE MINERAL CONSTITUENTS AND ALGÆ OF THE HOT-SPRINGS OF BEHAR, THE
HIMALAYA, AND OTHER PARTS OF INDIA, ETC., INCLUDING NOTES ON THE FUNGI
OF THE HIMALAYA.
(By Dr. R. D. Thomson and the Rev. M. J. Berkeley, M.A., F.L.S.)
The following remarks, for which I am indebted to the kindness of the
able chemist and naturalist mentioned above, will be highly valued,
both by those who are interested in the many curious physiological
questions involved in the association of the most obscure forms of
vegetable life with the remarkable phenomena of mineral springs; or in
the exquisitely beautiful microscopic structure of the lower Algæ,
which has thrown so much light upon a branch of natural history, whose
domain, like that of astronomy, lies to a great extent beyond the reach
of the unassisted eye.—J.D.H.
1. Mineral water, Soorujkoond, Behar (vol. i., p. 27), contains
chloride of sodium and sulphate of soda.
2. Mineral water, hot springs, Yeumtong, altitude 11,730 feet (see vol.
ii., p. 117). Disengages sulphuretted hydrogen when fresh.—This water
was inodorous when the bottle was opened. The saline matter in solution
was considerably less than in the Soorujkoond water, but like that
consisted of chloride of sodium and sulphate of soda. Its alkaline
character suggests the probability of its containing carbonate of soda,
but none was detected. The rocks decomposed by the waters of the spring
consist of granite impregnated with sulphate of alumina. It appears
that in this case the sulphurous waters of Yeumtong became impregnated
in the air with sulphuric acid, which decomposed the felspar,[397] and
united with its alumina. I found traces only of potash in the salt.
[397] I have, in my journal, particularly alluded to the garnets (an
aluminous mineral) being thus entirely decomposed.—J.D.H.
Sulphuretted hydrogen waters appear to give origin to sulphuric acid,
when the water impregnated with the gas reaches the surface; and I have
fine fibrous specimens of sulphate of lime accompanied with sulphur,
from the hot springs of Pugha in west Tibet, brought by Dr. T. Thomson.
3. Mineral water, Momay hot springs, (vol. ii., p. 133).—When the
bottle was uncorked, a strong smell of sulphuretted hydrogen was
perceived. The water contains about twenty-five grains per imp. gallon,
of chloride of sodium, sulphate and carbonate of soda; the reaction
being strongly alkaline when the solution was concentrated.
4. Effloresced earth from Behar (vol. i., p. 13), consists of granite
sand, mixed with sesquicarbonate of soda.
_On the Indian Algæ which occur principally in different parts of the
Himalayan Range, in the hot-springs of Soorujkoond in Bengal, Pugha in
Tibet, and Momay in Sikkim; and on the Fungi of the Himalayas._ By the
Rev. M. J. Berkeley, M.A.
It is not my intention in the present appendix to give specific
characters or even accurately determined specific names to the
different objects within its scope, which have come under
investigation, as collected by Dr. Hooker and Dr. Thomson. To do so
would require far more time than I have at present been able to devote
to the subject, for though every species has been examined
microscopically, either by myself or Mr. Broome, and working sketches
secured at the same time, the specific determination of fresh water
Algæ from Herbarium specimens is a matter which requires a very long
and accurate comparison of samples from every available locality, and
in the case of such genera as _Zygnema, Tyndaridea,_ and _Conferva,_
is, after all, not a very satisfactory process.
The object in view is merely to give some general notion of the forms
which presented themselves in the vast districts visited by the
above-mentioned botanists, comprising localities of the greatest
possible difference as regards both temperature and elevation; but more
especially in the hot-springs which occur in two distant parts of the
Himalayas and in Behar, and these again under very different degrees of
elevation and of extrinsic temperature.
The Algæ from lower localities are but few in number, and some of these
of very common forms. We have for instance from the Ganges, opposite
Bijnour, a _ Batrachospermum_ and _Conferva crispata,_ the former
purple below, with specimens of _Chantransia,_ exactly as they might
occur in the Thames. The _Conferva,_ or more properly _ Cladophora,_
which occurs also under various forms, at higher elevations, as in the
neighbourhood of Simla and Iskardo, swarms with little parasites, but
of common or uninteresting species. In the Bijnour specimens, these
consist of common forms of _Synedra, Meridion circulare,_ and a
_Cymbella,_ on others from Dacca, there are about three species of
_Synedra,_[398] a minute _Navicula_ and _Gomphonema curvatum._ Nothing,
in fact, can well be more European. One splendid Alga, however, occurs
at Fitcoree, in Behar, on the banks of nullahs, which are dry in hot
weather, forming a purple fleece of coarse woolly hairs, which are
singularly compressed, and of extreme beauty under the microscope, from
the crystalline green of the articulated string which threads the
bright red investing sheath. This curious Alga calls to mind in its
colouring _Cænocoleus Smithii,_ figured in English Botany, t. 2940, but
it has not the common sheath of that Alga, and is on a far larger
scale. One or two other allied forms, or species, occur in East Nepal,
to which I purpose giving, together with the Behar plant, the generic
name of _Erythronema._ From the Soane River, also, is an interesting
Alga, belonging to the curious genus _Thwaitesia,_ in which the
division of the endochrome in the fertile cells into four distinct
masses, sometimes entirely free, is beautifully marked. In some cases,
indeed, instead of the ordinary spores, the whole moss is broken up
into numerous bodies, as in the fertile joints of _Ulothrix,_ and
probably, as in that case, the resultant corpuscles are endowed with
active motion. In Silhet, again, is a magnificent _ Zygnema,_ allied to
_Z. nitidum,_ with large oval spores, about 1/285 part of an inch long,
and a dark golden brown colour, and containing a spiral green
endochrome.
[398] Two of these appear to be _S. Vaucheriæ_ and _S. inæqualis._
Leaving, however, the lower parts of India, I shall first take the
species which occur in Khasia, Sikkim, Eastern Nepal, and the adjoining
parts of Tibet.
In the hot valleys of the Gtreat Rungeet, at an elevation of about 2000
feet, we have the _Erythronema,_ but under a slightly different form;
at Nunklow, at about the same height; in Khasia, again, at twice that
elevation; in Eastern Nepal, at 12,000; and, finally, at Momay,
reaching up to 16,000 feet. In water, highly impregnated with oxide of
iron, at 4000 feet in Sikkim, a _Leptothrix_ occurred in great
abundance, coloured with the oxide, exactly as is the case with Algæ
which grow in iron springs in Europe. At elevations between 5000 and
7000 feet, several European forms occur, consisting of _ Ulothrix,
Zygnema, Oscillatoria, Lyngbya, Sphærozyga, Scytonema, Conferva,_ and
_Cladophora._ The species may indeed not be identical with European
species, but they are all more or less closely allied to well-known
Hydrophytes. One very interesting form, however, either belonging to
the genus _ Zygnema,_ or possibly constituting a distinct genus, occurs
in streams at 5000 feet in Sikkim, consisting of highly gelatinous
threads of the normal structure of the _Zygnema,_ but forming a
reticulated mass. The threads adhere to each other laterally,
containing only a single spiral endochrome, and the articulations are
very long. Amongst the threads are mixed those of some species of
_Tyndaridea._ There is also a curious _Hormosiphon,_ at a height of
7000 feet; forming anastomosing gelatinous masses. A fine new species
of _Lyngbya_ extends up as high as 11,000 feet. At 13,000 feet occurs
either some simple _Conferva_ or _Zygnema,_ it is doubtful which from
the condition of the specimens; and at the same elevation, in the
nearly dry bed of the stream which flows from the larger lake at Momay,
amongst flat cakes, consisting of felspathic silt from the glaciers
above, and the débris of Algæ, and abounding in Diatomaceæ, some
threads of a _Zygnema._ At 17,000 feet, an _ Oscillatoria,_ attached or
adherent to _Zannichellia_; and, finally, on the bare ground, at 18,000
feet, on the Donkia mountains, an obscure species of _Cænocoleus._ On
the surface of the glaciers at Kinchinjhow, on silt, there is a curious
_Palmella,_ apparently quite distinct from any European form.
Amongst the greater part of the Algæ, from 4000 feet to 18,000 feet,
various Diatomaceæ occur, which will be best noticed in a tabular form,
as follows; the specific name, within brackets, merely indicating the
species to which they bear most resemblance:—
Himantidium (_Soleirolii_)
Odontidium (_hiemale,_ forma minor)
Epithemia, _n. sp._
Cymbella
Navicula, _n. sp._
Tabillaria (_flocculosa_
Odontidium (_hiemale_)
Himantidium
Odontidium (_turgidulum_)
Epithemia (_ocellata_)
Fragillaria
Odontidium (_turgidulum_)
Dictyocha (_gracilis_)
Odontidium (_hiemale_) 4000 to 7000 feet
5000 to 7000 feet
7000 feet
—
—
6000 to 7000 feet
11,000 feet
16,000 feet
17,000 feet
—
18,000 feet
—
—
— Sikkim
Sikkim
Sikkim
Sikkim
Sikkim
Sikkim
Sikkim
Momay
Momay
Tibet
Momay
Momay
Momay
Kinchinjhow
We now turn to those portions of Tibet or the neighbouring regions,
explored by Dr. Thomson and Captain Strachey. The principal feature in
the Algology is the great prevalence of species of _Zygnema_ and
_Tyndaridea,_ which occur under a variety of forms, sometimes with very
thick gelatinous coats. In not a single instance, however, is there the
slightest tendency to produce fructification. _Conferva crispata_
again, as mentioned above, occurs in several localities; and in one
locality a beautiful unbranched _Conferva,_ with torulose
articulations. At Iskardo, Dr. Thomson gathered a very gelatinous
species of _Draparnaldia,_ or more properly, a _ Stygeoclonium,_ if we
may judge from a little conglomeration of cells which appeared amongst
the threads. A _Tetraspora_ in Piti, an obscure _Tolypothrix,_ and one
or two _ Oscillatoriæ,_ remarkable for their interrupted mode of
growth, complete the list of Algæ, with the exception of one, to be
mentioned presently; as also of _Diatomaceæ,_ and of the species of
_Nostoc_ and _Hormosiphon,_ which occurred in great profusion, and
under several forms, sometimes attaining a very large size (several
inches across), especially in the districts of Le and Piti, and where
the soil or waters were impregnated with saline matters. It is well
known that some species of _Nostoc_ form an article of food in China,
and one was used for that purpose in a late Arctic expedition, as
reported by Dr. Sutherland; but it does not seem that any use is made
of them in Tibet, though probably all the large species would form
tolerable articles of food, and certainly, from their chemical
composition, prove very nutritious. One species is mentioned by Dr.
Thomson as floating, without any attachment, in the shallow water of
the pools scattered over the plains, on the Parang River, separated
only by a ridge of mountains from Piti, broad and foliaceous, and
scarcely different from the common _ Nostoc,_ which occurs in all parts
of the globe. I must not, however, neglect to record a very singular
new genus, in which the young threads have the characters of
_Tyndaridea,_ but, after a time, little swellings occur on their sides,
in which a distinct endochrome is formed, extending backwards into the
parent endochrome, separated from it by a well defined membrane, and
producing, either by repeated pullulation, a compound mass like that of
_Calothrix,_ or simply giving rise to a forked thread. In the latter
case, however, there is no external swelling, but a lateral endochrome
is formed, which, as it grows, makes its way through an aperture, whose
sides are regularly inflected. I have given to this curious production
the name of _Cladozygia Thomsoni._
The whole of the above Algæ occurred at heights varying from 10,000 to
15,500 feet. As in the Southern Himalayan Algæ, the specimens were
infested with many Diatomaceæ, amongst which the most conspicuous were
various _Cymbellæ_ and _Epithemiæ._ The following is a list of the
species observed.
Cymbella (_gastroides_).
Cymbella (_gracilis_).
Cymbella (_Ehrenbergii_)
and three others.
Odontidium (_hiemale_).
Odontidium (_mesodon_).
Odontidium _n. sp._
Epithemia _n. sp._
Synedra (_arcus_).
Synedra (_tenuis_).
Synedra (_æqualis_).
Denticula (_obtusa_).
Gomphonema (_abbreviatum_).
Meridion circulare.
There is very little identity between this list and that before given
from the Southern Himalayas, as is the case also with the other Algæ.
Till the species, however, have been more completely studied, a very
accurate comparison cannot be made.
In both instances the species which grow in hot springs have been
reserved in order to make their comparison more easy. I shall begin in
an inverse order, with those of the springs of Pugha in Tibet, which
attain a temperature of 174°. Two _ Confervæ_ only occur in the
specimens which have been preserved, viz., an _Oscillatoria_ allied to
that which I have called _O. interrupta,_ and a true _Conferva_
extremely delicate with very long articulations, singularly swollen at
the commissures. The _Diatomaceæ_ are:—
Odontidium (_hiemale_).
Odontidium (_mesodon_).
Odontidium _n. sp.,_ same as at Piti on _Conferva._
Denticula (_obtusa_).
Navicula.
Cymbella, three species.
Epithemia.
Scarcely any one of these except the _Navicula_ is peculiar to the
locality. A fragment apparently of some _ Closterium,_ the only one
which I have met with in the collection, accompanies one of the
specimens.
The hot springs of Momay, (temp. 110°) at 16,000 feet, produce a golden
brown _Cænocoleus_ representing a small form of _C. cirrhosus,_ and a
very delicate _ Sphærozyga,_ an _Anabaina,_ and _Tolypothrix_; and at
17,000 feet, a delicate green _Conferva_ with long even articulations.
With the latter is an _Odontidium_ allied to, or identical with _O.
turgidulum,_ and with the former a fine species of _Epithemia_
resembling in form, but not in marking, _E. Faba, E. (Zebra)_ a fine
_Navicula,_ perhaps the same with _N. major_ and _Fragilaria
(virescens)._[399] In mud from one of the Momay springs (_a_), I
detected _Epithemia (Broomeii n.s.),_ and two small _Naviculæ,_ and in
the spring (_c_) two species of _Epithemia_ somewhat like _E. Faba,_
but different from that mentioned above.
[399] Mr. Thomas Brightwell finds in a portion of the same specimen
_Epithemia alpestris, Surirella splendida, S. linearis,_ Smith,
_Pinnularia viridis,_ Smith, _Navicula (lanceolata)_ and _Himantidium
(arcus)._
The hot springs of Soorujkoond, of the vegetation of which very
numerous specimens have been preserved, are extremely poor in species.
In the springs themselves and on their banks, at temperatures varying
from 80° to 158°, at which point vegetation entirely ceases, a minute
_Leptothrix_ abounds everywhere, varying a little in the regularity of
the threads in different specimens, but scarcely presenting two
species. Between 84° and 112° there is an imperfect _Zygnema_ with very
long articulations, and where the green scum passes into brown, there
is sometimes an _Oscillatoria,_ of a very minute stellate _Scytonema,_
probably in an imperfect state. _ Epithemia ocellata_ also contributes
often to produce the tint. An _Anabaina_ occurs at a temperature of
125°, but the same species was found also in the stream from the
springs where the water had become cold, as was also the case with the
_ Zygnema._
The Diatomaceæ consisted of:—
Epithemia Broomeii, _n. s._
Epithemia thermalis, _n. sp._
Epithemia inæqualis, _n. sp._
Navicula Beharensis, _n. sp._
The vegetation in the three sets of springs was very different. As
regards the _Confervæ,_ taking the word in its older sense, the species
in the three are quite different, and even in respect of genera there
is little identity, but amongst the _Diatomaceæ_ there is no striking
difference, except in those of the Behar springs where three out of the
four did not occur elsewhere. In the Pugha and Momay springs, the
species were either identical with, or nearly allied to those found in
neighbouring localities, where the water did not exceed the ordinary
temperature. A longer examination will doubtless detect more numerous
forms, but those which appear on a first examination are sure to give a
pretty correct general notion of the vegetation. The species are
certainly less numerous than I had expected, or than might be supposed
from the vegetation of those European hot springs which have been most
investigated.
In conclusion, I shall beg to add a few words on the Fungi of the
Himalayas, so far as they have at present been investigated. As regards
these there is a marked difference, as might be anticipated from the
nature of the climates between those parts of Tibet investigated by Dr.
Thomson, and the more southern regions. The fungi found by Dr. Thomson
were but few in number, and for the most part of very ordinary forms,
differing but little from the produce of an European wood. Some,
however, grow to a very large size, as for instance, _Polyporus
fomentarius_ on poplars near Iskardo, exceeding in dimensions anything
which this species exhibits in Europe. A very fine _Æcidium_ also
infests the fir trees (_Abies Smithiana_), a figure of which has been
given in the “Gardeners’ Chronicle,” 1852, p. 627, under the name of
_Æcidium Thomsoni._ This is allied to the Hexenbesen of the German
forests, but is a finer species and quite distinct. _Polyporus
oblectans, Geaster limbatus, Geaster mammosus, Erysiphe taurica,_ a
_Boletus_ infested with _Sepedonium mycophilum, Scleroderma
verrucosum,_ an _Æcidium,_ and a _Uromyces,_ both on _Mulgedium
Tataricum,_ about half-a-dozen Agarics, one at an altitude of 16,000
feet above the Nubra river, a _Lycoperdon,_ and _ Morchella
semilibera,_ which is eaten in Kashmir, and exported when dry to the
plains of India, make up the list of fungi.
The region of Sikkim is perhaps the most productive in fleshy fungi of
any in the world, both as regards numbers and species, and Eastern
Nepal and Khasia yield also an abundant harvest. The forms are for the
most part European, though the species are scarcely ever quite
identical. The dimensions of many are truly gigantic, and many species
afford abundant food to the natives. Mixed with European forms a few
more decidedly tropical occur, and amongst those of East Nepal is a
_Lentinus_ which has the curious property of staining every thing which
touches it of a deep rhubarb yellow, and is not exceeded in
magnificence by any tropical species. The _Polypori_ are often
identical with those of Java, Ceylon, and the Philippine Isles, and the
curious _Trichocoma paradoxum_ which was first found by Junghuhn in
Java, and very recently by Dr. Harvey in Ceylon, occurs abundantly on
the decayed trunks of laurels, as it does in South Carolina. The
curious genus _Mitremyces_ also is scattered here and there, though not
under the American form, but that which occurs in Java. Though
_Hymenomycetes_ are so abundant, the _ Discomycetes_ and _Ascomycetes_
are comparatively rare, and very few species indeed of _Sphœria_ were
gathered. One curious matter is, that amongst the very extensive
collections which have been made there is scarcely a single new genus.
The species moreover in Sikkim are quite different, except in the case
of some more or less cosmopolite species from those of Eastern Nepal
and Khasia: scarcely a single _Lactarius_ or _ Cortinarius_ for
instance occurs in Sikkim, though there are several in Khasia. The
genus _Boletus_ through the whole district assumes the most magnificent
forms, which are generally very different from anything in Europe.
C.
ON THE SOILS OF SIKKIM.
There is little variety in the soil throughout Sikkim, and, as far as
vegetation is concerned, it may be divided into vegetable mould and
stiff clay—each, as they usually occur, remarkably characteristic in
composition of such soils. Bog-earth is very rare, nor did I find peat
at any elevation.
The clay is uniformly of great tenacity, and is, I believe, wholly due
to the effect of the atmosphere on crumbling gneiss and other rocks. It
makes excellent bricks, is tenacious, seldom friable, and sometimes
accumulated in beds fourteen feet thick, although more generally only
about two feet. In certain localities, beds or narrow seams of pure
felspathic clay and layers of vegetable matter occur in it, probably
wholly due to local causes. An analysis of that near Dorjiling gives
about 30 per cent. of alumina, the rest being silica, and a fraction of
oxide of iron. Lime is wholly unknown as a constituent of the soil, and
only occasionally seen as a stalactitic deposit from a few springs.
A layer of vegetable earth almost invariably covers the clay to the
depth of from three to twelve or fourteen inches. It is a very rich
black mould, held in its position on the slopes of the hills by the
dense vegetation, and accumulated on the banks of small streams to a
depth at times of three and four feet. The following is an analysis of
an average specimen of the surface-soil of Dorjiling, made for me by my
friend C. J. Muller, Esq., of that place:—
_a._—DRY EARTH
Anhydrous
Water 83·84
16·16
————
100·00
_b._—ANHYDROUS EARTH
Humic acid
Humine
Undecomposed vegetable matter
Peroxide of iron and manganese
Alumina
Siliceous matter, insoluble in dilute hydrochloric acid
Traces of soda and muriatic acid 3·89
4·61
20·98
7·05
8·95
54·52
--
————
100·00
_c._—Soluble in water, gr. 1·26 per cent., consisting of soda, muriatic
acid, organic matter, and silica.
The soil from which this example was taken was twelve inches deep; it
abounded to the eye in vegetable matter, and was siliceous to the
touch. There were no traces of phosphates or of animal matter, and
doubtful traces of lime and potash. The subsoil of clay gave only 5·7
per cent. of water, and 5·55 of organic matter. The above analysis was
conducted during the rainy month of September, and the sample is an
average one of the surface-soil at 6000 to 10,000 feet. There is, I
think, little difference anywhere in the soils at this elevation,
except where the rock is remarkably micaceous, or where veins of
felspathic granite, by their decomposition, give rise to small beds of
kaolin.
D.
(Vol. i., p. 37)
AN AURORA SEEN FROM BAROON ON THE EAST BANK
OF THE SOANE RIVER.
Lat. 24° 52′ N.; Long. 84° 22′ E.; Alt. 345 feet.
The following appearances are as noted in my journal at the time. They
so entirely resembled auroral beams, that I had no hesitation in
pronouncing them at the time to be such. This opinion has, however,
been dissented from by some meteorologists, who consider that certain
facts connected with the geographical distribution of auroras (if I may
use the term), are opposed to it. I am well aware of the force of these
arguments, which I shall not attempt to controvert; but for the
information of those who may be interested in the matter, I may remark,
that I am very familiar with the Aurora borealis in the northern
temperate zone, and during the Antarctic expedition was in the habit of
recording in the log-book the appearance presented by the Aurora
australis. The late Mr. Williams, Mr. Haddon, and Mr. Theobald, who
were also witnesses of the appearances on this occasion, considered it
a brilliant display of the aurora.
_Feb. 14th,_ 9 p.m.—Bax. Corr. 29·751; temp. 62°; D.P. 41·0°; calm, sky
clear; moon three-quarters full, and bright.
Observed about thirty lancet beams rising in the north-west from a low
luminous arch, whose extremes bore W. 20° S., and N. 50° E.; altitude
of upper limb of arch 20°, of the lower 8°. The beams crossed the
zenith, and converged towards S. 15° E. The extremity of the largest
was forked, and extended to 25° above the horizon in the S.E. by S.
quarter. The extremity of the centre one bore S. 50° E., and was 45°
above the horizon. The western beams approached nearest the southern
horizon. All the beams moved and flashed slowly, occasionally splitting
and forking, fading and brightening; they were brightly defined, though
the milky way and zodiacal light could not be discerned, and the stars
and planets, though clearly discernible, were very pale.
At 10 p.m., the luminous appearance was more diffused; upper limb of
the arch less defined; no beams crossed the zenith; but occasionally
beams appeared there and faded away.
Between 10 and 11, the beams continued to move and replace one another,
as usual in auroras, but disappeared from the south-east quarter, and
became broader in the northern hemisphere; the longest beams were near
the north and north-east horizon.
At half-past 10, a dark belt, 4° broad, appeared in the luminous arch,
bearing from N. 55° W. to N. 10° W.; its upper limb was 10° above the
horizon: it then gradually dilated, and thus appeared to break up the
arch. This appeared to be the commencement of the dispersion of the
phenomenon.
At 10.50 p.m. the dark band had increased so much in breadth that the
arch was broken up in the north-west, and no beams appeared there.
Eighteen linear beams rose from the eastern part of the arch, and bore
from north to N. 20° E.
Towards 11 p.m., the dark band appeared to have replaced the luminous
arch; the beams were all but gone, a few fragments appearing in the
N.E. A southerly wind sprang up, and a diffused light extended along
the horizon.
At midnight, I saw two faint beams to the north-east, and two well
defined parallel ones in the south-west.
E.
PHYSICAL GEOGRAPHY OF THE SIKKIM HIMALAYA, EAST NEPAL,
AND ADJACENT PROVINCES OF TIBET.
Sikkim is included in a section of the Himalaya, about sixty miles
broad from east to west, where it is bounded respectively by the
mountain states of Bhotan and Nepal. Its southern limits are easily
defined, for the mountains rise abruptly from the plains of Bengal, as
spurs of 6000 to 10,000 feet high, densely clothed with forest to their
summits. The northern and north-eastern frontier of Sikkim is beyond
the region of much rain, and is not a natural, but a political line,
drawn between that country and Tibet. Sikkim lies nearly due north of
Calcutta, and only four hundred miles from the Bay of Bengal; its
latitude being 26° 40′ to 28° N., and longitude 88° to 89° E.
The main features of Sikkim are Kinchinjunga, the loftiest hitherto
measured mountain, which lies to its north-west, and rises 28,178 feet
above the level of the sea; and the Teesta river, which flows
throughout the length of the country, and has a course of upwards of
ninety miles in a straight line. Almost all the sources of the Teesta
are included in Sikkim; and except some comparatively insignificant
streams draining the outermost ranges, there are no rivers in this
country but itself and its feeders, which occupy the largest of the
Himalayan valleys between the Tambur in East Nepal, and the Machoo in
Western Bhotan.
An immense spur, sixty miles long, stretches south from Kinchin to the
plains of India; it is called Singalelah, and separates Sikkim from
East Nepal; the waters from its west flank flow into the Tambur, and
those from the east into the Great Rungeet, a feeder of the Teesta.
Between these two latter rivers is a second spur from Kinchinjunga,
terminating in Tendong.
The eastern boundary of Sikkim, separating it from Bhotan, is formed
for the greater part by the Chola range, which stretches south from the
immense mountain of Donkia, 23,176 feet high, situated fifty miles
E.N.E. of Kinchinjunga: where the frontier approaches the plains of
India, the boundary line follows the course of the Teesta, and of the
Rinkpo, one of its feeders, flowing from the Chola range. This range is
much more lofty than that of Singalelah, and the drainage from its
eastern flank is into the Machoo river, the upper part of whose course
is in Tibet, and the lower in Bhotan.
The Donkia mountain, though 4000 feet lower than Kinchin, is the
culminant point of a much more extensive and elevated mountain mass. It
throws off an immense spur from its north-west face, which runs west,
and then south-west, to Kinchin, forming the watershed of all the
remote sources of the Teesta. This spur has a mean elevation of 18,000
to 19,000 feet, and several of its peaks (of which Chomiomo is one)
rise much higher. The northern boundary of Sikkim is not drawn along
this, but runs due west from Donkia, following a shorter, but
stupendous spur, called Kinchinjhow; whence it crosses the Teesta to
Chomiomo, and is continued onwards to Kinchinjunga.
Though the great spur connecting Donkia with Kinchin is in Tibet, and
bounds the waters that flow directly south into the Teesta, it is far
from the true Himalayan axis, for the rivers that rise on its northern
slope do not run into the valley of the Tsampu, or Tibetan
Burrampooter, but into the Arun of Nepal, which rises to the north of
Donkia, and flows south-west for many miles in Tibet, before entering
Nepal and flowing south to the Ganges.
Sikkim, thus circumscribed, consists of a mass of mountainous spurs,
forest-clad up to 12,000 feet; there are no flat valleys or plains in
the whole country, no lakes or precipices of any consequence below that
elevation, and few or no bare slopes, though the latter are uniformly
steep. The aspect of Sikkim can only be understood by a reference to
its climate and vegetation, and I shall therefore take these together,
and endeavour, by connecting these phenomena, to give an intelligible
view of the main features of the whole country.[400]
[400] This I did with reference especially to the cultivation of
Rhododendrons, in a paper which the Horticultural Society of London
did me the honour of printing. Quarterly Journ. of Hort. Soc., vol.
vii., p. 82.
The greater part of the country between Sikkim and the sea is a dead
level, occupied by the delta of the Ganges and Burrampooter, above
which the slope is so gradual to the base of the mountains, that the
surface of the plain from which the Himalayas immediately rise is only
300 feet above the sea. The most obvious effect of this position is,
that the prevailing southerly wind reaches the first range of hills,
loaded with vapour. The same current, when deflected easterly to
Bhotan, or westerly to Nepal and the north-west Himalaya, is
intercepted and drained of much moisture, by the Khasia and Garrow
mountains (south of Assam and the Burrampooter) in the former case, and
the Rajmahal hills (south of the Ganges) in the latter. Sikkim is hence
the dampest region of the whole Himalaya.
Viewed from a distance on the plains of India, Sikkim presents the
appearance—common to all mountainous countries—of consecutive parallel
ridges, running east and west: these are all wooded, and backed by a
beautiful range of snowy peaks, with occasional breaks in the foremost
ranges, through which the rivers debouch. Any view of the Himalaya,
especially at a sufficient distance for the remote snowy peaks to be
seen overtopping the outer ridges, is, however, rare, from the constant
deposition of vapours over the forest-clad ranges during the greater
part of the year, and the haziness of the dry atmosphere of the plains
in the winter months. At the end of the rains, when the south-east
monsoon has ceased to blow with constancy, views are obtained,
sometimes from a distance of nearly two hundred miles. From the plains,
the highest peaks subtend so small an angle, that they appear like
white specks very low on the horizon, tipping the black lower and outer
wooded ranges, which always rise out of a belt of haze, and from the
density, probably, of the lower strata of atmosphere, are never seen to
rest on the visible horizon. The remarkable lowness on the horizon of
the whole stupendous mass is always a disappointing feature to the new
comer, who expects to see dazzling peaks towering in the air.
Approaching nearer, the snowy mountains sink behind the wooded ones,
long before the latter have assumed gigantic proportions; and when they
do so, they appear a sombre, lurid grey-green mass of vegetation, with
no brightness or variation of colour. There is no break in this forest
caused by rock, precipices, or cultivation; some spurs project nearer,
and some valleys appear to retire further into the heart of the
foremost great chain that shuts out all the country beyond.
From Dorjiling the appearance of parallel ridges is found to be
deceptive, and due to the inosculating spurs of long tortuous ranges
that ran north and south throughout the whole length of Sikkim,
dividing deep wooded valleys, which form the beds of large rivers. The
snowy peaks here look like a long east and west range of mountains, at
an average distance of thirty or forty miles. Advancing into the
country, this appearance proves equally deceptive, and the snowy range
is resolved into isolated peaks, situated on the meridional ridges;
their snow-clad spurs, projecting east and west, cross one another, and
being uniformly white, appear to connect the peaks into one grand
unbroken range. The rivers, instead of having their origin in the snowy
mountains, rise far beyond them; many of their sources are upwards of
one hundred miles in a straight line from the plains, in a very curious
country, loftier by far in mean elevation than the meridional ridges
which run south from it, yet comparatively bare of snow. This rearward
part of the mountain region is Tibet, where all the Sikkim, Nepal, and
Bhotan rivers rise as small streams, increasing in size as they receive
the drainage from the snowed parts of the ridges that bound them in
their courses. Their banks, between 8000 and 14,000 feet, are generally
clothed with rhododendrons, sometimes to the almost total exclusion of
other woody vegetation, especially near the snowy mountains—a cool
temperature and great humidity being the most favourable conditions for
the luxuriant growth of this genus.
The source of this humidity is the southerly or sea wind which blows
steadily from May till October in Sikkim, and prevails throughout the
rest of the year, if not as the monsoon properly so called, as a
current from the moist atmosphere above the Gangetic delta. This rushes
north to the rarefied regions of Sikkim, up the great valleys, and does
not appear materially disturbed by the north-west wind, which blows
during the afternoons of the winter months over the plains, and along
the flanks of the outer range, and is a dry surface current, due to the
diurnal heating of the soil. When it is considered that this wind,
after passing lofty mountains on the outer range, has to traverse
eighty or one hundred miles of alps before it has watered all the
forest region, it will be evident that its moisture must be expended
before it reaches Tibet.
Let the figures in the accompanying woodcut, the one on the true scale,
the other with the heights exaggerated, represent two of these long
meridional ridges, from the watershed to the plains of India, following
in this instance the course of the Teesta river, from its source at
19,000 feet to where it debouches from the Himalaya at 300. The lower
rugged outline represents one meridional ridge, with all its most
prominent peaks (whether exactly or not on the line of section); the
upper represents the parallel ridge of Singalelah (D.E.P.), of greater
mean elevation, further west, introduced to show the maximum elevation
of the Sikkim mountains, Kinchinjunga (28,178 feet), being represented
on it. A deep valley is interposed between these two ridges, with a
feeder of the Teesta in it (the Great Rungeet), which runs south from
Kinchin, and turning west enters the Teesta at R. The position of the
bed of the Teesta river is indicated by a dotted line from its source
at T to the plains at S; of Dorjiling, on the north flank of the outer
range, by _d_; of the first point where perpetual snow is met with, by
P; and of the first indications of a Tibetan climate, by C.
A warm current of Air, loaded with vapour, will deposit the bulk of its
moisture on the ridge of Sinchul, which rises above Dorjiling (_d_),
and is 8,500 feet high. Passing on, little will be precipitated on _e_
whose elevation is the same as that of Sinchul; but much at _f_ (11,000
feet), where the current, being further cooled, has less capacity for
holding vapour, and is further exhausted. When it ascends to P (15,000
feet) it is sufficiently cooled to deposit snow in the winter and
spring months, more of which falling than can be melted during the
summer, it becomes perennial. At the top of ginchin very little falls,
and it is doubtful if the southerly current ever reaches that
prodigiously elevated isolated summit. The amount of surface above
20,000 feet is, however, too limited and broken into isolated peaks to
drain the already nearly, exhausted current, whose condensed vapours
roll along in fog beyond the parallel of Kinchin, are dissipated during
the day over the arid mountains of Tibet, and deposited at night on the
cooled surface of the earth.
Section of the Sikkim Himalaya along the course of the Teesta River.
Other phenomena of no less importance than the distribution of vapour,
and more or less depending on it, are the duration and amount of solar
and terrestrial radiation. Towards D the sun is rarely seen during the
rainy season, as well from the constant presence of nimbi aloft, as
from fog on the surface of the ground. An absence of both light and
heat is the result south of the parallel of Kinchin; and at C low fogs
prevail at the same season, but do not intercept either the same amount
of light or heat; whilst at T there is much sunshine and bright light.
During the night, again, there is no terrestrial radiation between S
and P; the rain either continues to pour—in some months with increased
violence—or the saturated atmosphere is condensed into a thick white
mist, which hangs over the redundant vegetation. A bright starlight
night is almost unknown in the summer months at 6000 to 10,000 feet,
but is frequent in December and January, and at intervals between
October and May, when, however, vegetation is little affected by the
cold of nocturnal radiation. In the regions north of Kinchin, starlight
nights are more frequent, and the cold produced by radiation, at 14,000
feet, is often severe towards the end of the rains in September. Still
the amount of clear weather during the night is small; the fog clears
off for an hour or two at sunset as the wind falls, but the returning
cold north current again chills the air soon afterwards, and rolling
masses of vapour are hence flying overhead, or sweeping the surface of
the earth, throughout the summer nights. In the Tibetan regions, on the
other hand, bright nights and even sharp frosts prevail throughout the
warmest months.
Referring again to the cut, it must be borne in mind that neither of
the two meridional ridges runs in a straight line, but that they wind
or zigzag as all mountain ranges do; that spurs from each ridge are
given off from either flank alternately, and that the origin of a spur
on one side answers to the source of a river (_i.e.,_ the head of a
valley) on the other. These rivers are feeders of the main stream, the
Teesta, and run at more or less of an angle to the latter. The spurs
from the east flank of one ridge cross, at their ends, those from the
west flank of another; and thus transverse valleys are formed,
presenting many modifications of climate with regard to exposure,
temperature, and humidity.
The roads from the plains of India to the watershed in Tibet always
cross these lateral spurs. The main ridge is too winding and rugged,
and too lofty for habitation throughout the greater part of its length,
while the river-channel is always very winding, unhealthy for the
greater part of the year below 4000 feet, and often narrow, gorge-like,
and rocky. The villages are always placed above the unhealthy regions,
on the lateral spurs, which the traveller repeatedly crosses throughout
every day’s march; for these spurs give off lesser ones, and these
again others of a third degree, whence the country is cut up into as
many spurs, ridges, and ranges, as there are rills, streams, and rivers
amongst the mountains.
Though the direction of the main atmospheric current is to the north,
it is in reality seldom felt to be so, except the observer be on the
very exposed mountain tops, or watch the motions of the upper strata of
atmosphere. Lower currents of air rush up both the main and lateral
valleys, throughout the day; and from the sinuosities in the beds of
the rivers, and the generally transverse directions of their feeders,
the current often becomes an east or west one. In the branch valleys
draining to the north the wind still ascends; it is, in short, an
ascending warm, moist current, whatever course be pursued by the
valleys it follows.
The sides of each valley are hence equally supplied with moisture,
though local circumstances render the soil on one or the other flank
more or less humid and favourable to a luxuriant vegetation: such
differences are a drier soil on the north side, with a too free
exposure to the sun at low elevations, where its rays, however
transient, rapidly dry the ground, and where the rains, though very
heavy, are of shorter duration, and where, owing to the capacity of the
heated air for retaining moisture, day fogs are comparatively rare. In
the northern parts of Sikkim, again, some of the lateral valleys are so
placed that the moist wind strikes the side facing the south, and keeps
it very humid, whilst the returning cold current from the neighbouring
Tibetan mountains impinges against the side facing the north, which is
hence more bare of vegetation. An infinite number of local
peculiarities will suggest themselves to any one conversant with
physical geography, as causing unequal local distribution of light,
heat, and moisture in the different valleys of so irregular a country;
namely, the amount of slope, and its power of retaining moisture and
soil; the composition and hardness of the rocks; their dip and strike;
the protection of some valleys by lofty snowed ridges; and the free
southern exposures of others at great elevations.
The position and elevation of the perpetual snow[401] vary with those
of the individual ranges, and their exposure to the south wind. The
expression that the perpetual snow lies lower and deeper on the
southern slopes of the Himalayan mountains than on the northern,
conveys a false impression. It is better to say that the snow lies
deeper and lower on the southern faces of the individual mountains and
spurs that form the snowy Himalaya. The axis itself of the chain is
generally far north of the position of the spurs that catch all the
snow, and has comparatively very little snow on it, most of what there
is lying upon north exposures.
[401] It appears to me, as I have asserted in the pages of my Journal,
that the limit of perpetual snow is laid down too low in all mountain
regions, and that accumulations in hollows, and the descent of glacial
ice, mask the phenomenon more effectually than is generally allowed.
In this work I define the limit, as is customary, in general terms
only, as being that where the accumulations are very great, and whence
they are continuous upwards, on gentle slopes. All perpetual snow,
however, becomes ice, and, as such, obeys the laws of glacial motion,
moving as a viscous fluid; whence it follows that the lower edge of a
snow-bed placed on a slope is, in one sense, the termination of a
glacier, and indicates a position below that where all the snow that
falls melts. I am well aware that it is impossible to define the limit
required with any approach to accuracy. Steep and broken surfaces,
with favourable exposures to the sun or moist winds, are bare much
above places where snow lies throughout the year; but the occurrence
of a gentle slope, free of snow, and covered with plants, cannot but
indicate a point below that of perpetual snow. Such is the case with
the “Jardin” on the Mer de Glace, whose elevation is 9,500 feet,
whereas that of perpetual snow is considered by Professor J. Forbes,
our best authority, to be 8,500 feet. Though limited in area, girdled
by glaciers, presenting a very gentle slope to the east, and screened
by surrounding mountains from a considerable proportion of the sun’s
rays, the Jardin is clear, for fully three months of the year, of all
but sporadic falls of snow, that never lie long; and so are similar
spots placed higher on the neighbouring slopes; which facts are quite
at variance with the supposition that the perpetual snow-line is below
that point in the Mont Blanc Alps. On the Monte Rosa Alps, again, Dr.
Thomson and I gathered plants in flower, above 12,000 feet on the
steep face of the Weiss-thor Pass, and at 10,938 feet on the top of
St. Theodule; but in the former case the rocks are too steep for any
snow to lie, they are exposed to the south-east, and overhang a gorge
8000 feet deep, up which no doubt warm currents ascend; while at St.
Theodule the plants were growing on a slope which, though gentle, is
black and stony, and exposed to warm ascending currents, as on the
Weiss-thor; and I do not consider either of these as evidences of the
limit of perpetual snow being higher than their position.
A reference to the woodcut will show that the same circumstances which
affect the distribution of moisture and vegetation, determine the
position, amount, and duration of the snow. The principal fall will
occur, as before shown, where the meridional range first attains a
sufficiently great elevation, and the air becomes consequently cooled
below 32°; this is at a little above 14,000 feet, sporadic falls
occurring even in summer at that elevation: these, however, melt
immediately, and the copious winter falls also are dissipated before
June. As the depth of rain-fall diminishes in advancing north to the
higher parts of the meridional ranges, so does that of the snow-fall.
The permanence of the snow, again, depends on—1. The depth of the
accumulation; 2. The mean temperature of the spot; 3. The melting power
of the sun’s rays; 4. The prevalence and strength of evaporating winds.
Now at 14,000 feet, though the accumulation is immense, the amount
melted by the sun’s rays is trifling, and there are no evaporating
winds; but the mean temperature is so high, and the corroding powers of
the rain (which falls abundantly throughout summer) and of the warm and
humid ascending currents are so great, that the snow is not perennial.
At 15,500 feet, again, it becomes perennial, and its permanence at this
low elevation (at P) is much favoured by the accumulation and detention
of fogs over the rank vegetation which prevails from S nearly to P; and
by the lofty mountains beyond it, which shield it from the returning
dry currents from the north. In proceeding north all the circumstances
that tend to the dispersion of the snow increase, whilst the fall
diminishes. At P the deposition is enormous and the snow-line
low—16,000 feet; whilst at T little falls, and the limit of perpetual
snow is 19,000 and 20,000 feet. Hence the anomaly, that the snow-line
ascends in advancing north to the coldest Himalayan regions. The
position of the greatest peaks and of the greatest mass of perpetual
snow being generally assumed as indicating a ridge and watershed,
travellers, arguing from single mountains alone, on the meridional
ridges, have at one time supported and at another denied the assertion,
that the snow lies longer and deeper on the north than on the south
slope of the Himalayan ridge.
The great accumulation of snow at 15,000 feet, in the parallel of P,
exercises a decided influence on the vegetation. The alpine
rhododendrons hardly reach 14,000 feet in the broad valleys and
round-headed spurs of the mountains of the Tunkra and Chola passes;
whilst the same species ascend to 16,000, and one to 17,000 feet, at T.
Beyond the latter point, again, the great aridity of the climate
prevents their growth, and in Tibet there are generally none even as
low as 12,000 and 14,000 feet. Glaciers, again, descend to 15,000 feet
in the tortuous gorges which immediately debouch from the snows of
Kinchinjunga, but no plants grow on the débris they carry down, nor is
there any sward of grass or herbage at their base, the atmosphere
immediately around being chilled by enormous accumulations of snow, and
the summer sun rarely warming the soil. At T, again, the glaciers do
not descend below 16,000 feet, but a greensward of vegetation creeps up
to their bases, dwarf rhododendrons cover the moraines, and herbs grow
on the patches of earth carried down by the latter, which are thawed by
the more frequent sunshine, and by the radiation of heat from the
unsnowed flanks of the valleys down which these ice-streams pour.
Looking eastward or westward on the map of India, we perceive that the
phenomenon of perpetual snow is regulated by the same laws. From the
longitude of Upper Assam in 95° E to that of Kashmir in 75° E, the
lowest limit of perpetual snow is 15,500 to 16,000 feet, and a shrubby
vegetation affects the most humid localities near it, at 12,000 to
14,000 feet. Receding from the plains of India and penetrating the
mountains, the climate becomes drier, the snowline rises, and
vegetation diminishes, whether the elevation of the land increases or
decreases; plants reaching 17,000 and 18,000 feet, and the snow-line,
20,000 feet. To mention extreme cases; the snow-level of Sikkim in 27°
30 minutes is at 16,000 feet, whereas in latitude 35° 30 minutes Dr.
Thomson found the snow line 20,000 feet on the mountains near the
Karakoram Pass, and vegetation up to 18,500 feet—features I found to be
common also to Sikkim in latitude 28°.
The Himalaya, north of Nepal, and thence eastward to the bend of the
Yaru-Tsampu (or Tibetan Burrampooter) has for its geographical limits
the plains of India to the south, and the bed of the Yaru to the north.
All between these limits is a mountain mass, to which Tibet (though so
often erroneously called a plain)[402] forms no exception. The waters
from the north side of this chain flow into the Tsampu, and those from
the south side into the Burrampooter of Assam, and the Ganges. The
line, however tortuous, dividing the heads of these waters, is the
watershed, and the only guide we have to the axis of the Himalaya. This
has never been crossed by Europeans, except by Captain Turner’s embassy
in 1798, and Captain Bogle’s in 1779, both of which reached the Yaru
river. In the account published by Captain Turner, the summit of the
watershed is not rigorously defined, and the boundary, of Tibet and
Bhotan is sometimes erroneously taken for it; the boundary being at
that point a southern spur of Chumulari.[403] Eastwards from the
sources of the Tsampu, the watershed of the Himalaya seems to follow a
very winding course, and to be everywhere to the north of the snowy
peaks seen from the plains of India. It is by a line through these
snowy peaks that the axis of the Himalaya is represented in all our
maps; because they _ seem_ from the plains to be situated on an east
and west ridge, instead of being placed on subsidiary meridional
ridges, as explained above. It is also across or along the subsidiary
ridges that the boundary line between the Tibetan provinces and those
of Nepal, Sikkim, and Bhotan, is usually drawn; because the enormous
accumulations of snow form a more efficient natural barrier than the
greater height of the less snowed central part of the chain beyond
them.
[402] The only true account of the general features of eastern Tibet
is to be found in MM. Huc and Gabet’s travels. Their description
agrees with Dr. Thomson’s account of western Tibet, and with my
experience of the parts to the north of Sikkim, and the information I
everywhere obtained. The so-called _plains_ are the flat floors of the
valleys, and the terraces on the margins of the rivers, which all flow
between stupendous mountains. The term “maidan,” so often applied to
Tibet by the natives, implies, not a plain like that of India, but
simply an open, dry, treeless country, in contrast to the densely
wooded wet regions of the snowy Himalaya, south of Tibet.
[403] Between Donkia and Chumulari lies a portion of Tibet (including
the upper part of the course of the Machoo river) bounded on the east
by Bhotan, and on the west by Sikkim (see chapter xxii). Turner, when
crossing the Simonang Pass, descended westwards into the valley of the
Machoo, and was still on the Indian watershed.
Though, however, our maps draw the axis through the snowy peaks, they
also make the rivers to rise beyond the latter, on the northern slopes
as it were, and to flow southwards through gaps in the axis. Such a
feature is only reconcilable with the hypothesis of the chain being
double, as the Cordillera of Peru and Chili is said to be,
geographically, and which in a geological sense it no doubt is: but to
the Cordillera the Himalaya offers no parallel. The results of Dr.
Thomson’s study of the north-west Himalaya and Tibet, and my own of the
north-east extreme of Sikkim and Tibet, first gave me an insight into
the true structure of this chain. Donkia mountain is the culminant
point of an immensely elevated mass of mountains, of greater mean
height than a similarly extensive area around Kinchin junga. It
comprises Chumulari, and many other mountains much above 20,000 feet,
though none equalling Kinchinjunga, Junnoo, and Kubra. The great lakes
of Ramchoo and Cholamoo are placed on it; and the rivers rising on it
flow in various directions; the Painomchoo north-west into the Yaru;
the Arun west to Nepal; the Teesta south-west through Sikkim; the
Machoo south, and the Pachoo south-east, through Bhotan. All these
rivers have their sources far beyond the great snowed mountains, the
Arun most conspicuously of all, flowing completely at the back or north
of Kinchinjunga. Those that flow southwards, break through no chain,
nor do they meet any contraction as they pass the snowy parts of the
mountains which bound the valleys in which they flow, but are bound by
uniform ranges of lofty mountains, which become more snowy as they
approach the plains of India. These valleys, however, gradually
contract as they descend, being less open in Sikkim and Nepal than in
Tibet, though there bounded by rugged mountains, which from being so
bare of snow and of vegetation, do not give the same impression of
height as the isolated sharper peaks which rise out of a dense forest,
and on which the snow limit is 4000 or 5000 feet lower.
The fact of the bottom of the river valleys being flatter towards the
watershed, is connected with that of their fall being less rapid at
that part of their course; this is the consequence of the great extent
in breadth of the most elevated portion of the chain. If we select the
Teesta as an example, and measure its fall at three points of its
course, we shall find the results very different. From its principal
source at Lake Cholamoo, it descends from 17,000 to 15,000 feet, with a
fall of 60 feet to the mile; from 15,000 to 12,000 feet, the fall is
140 feet to the mile; in the third part of its course it descends from
12,000 to 5000 feet, with a fall of 160 feet to the mile; and in the
lower part the descent is from 5000 feet to the plains of India at 300
feet, giving a fall of 50 feet to the mile. There is, however, no
marked limit to these divisions; its valley. gradually contracts, and
its course gradually becomes more rapid. It is worthy of notice that
the fall is at its maximum through that part of its valley of which the
flanks are the most loaded with snow; where the old moraines are very
conspicuous, and where the present accumulations from landslips, etc.,
are the most extensive.[404]
[404] It is not my intention to discuss here the geological bearings
of this curious question; but I may state that as the humidity of the
climate of the middle region of the river-course tends to increase the
fall in a given space, so I believe the dryness of the climate of the
loftier country has the opposite effect, by preserving those
accumulations which have raised the floors of the valleys and rendered
them level.
With reference to Kinchinjunga, these facts are of importance, as
showing that mere elevation is in physical geography of secondary
importance. That lofty mountain rises from a spur of the great range of
Donkia, and is quite removed from the watershed or axis of the
Himalaya, the rivers which drain its northern and southern flanks alike
flowing to the Ganges. Were the Himalaya to be depressed 18,000 feet,
Kubra, Junnoo, Pundim, etc., would form a small cluster of rocky
islands 1000 to 7000 feet high, grouped near Kinchinjunga, itself a
cape 10,000 feet high, which would be connected by a low, marrow neck,
with an extensive and mountainous tract of land to its north-east; the
latter being represented by Donkia. To the north of Kinchin a deep bay
or inlet would occupy the present valley of the Arun, and would be
bounded on the north by the axis of the Himalaya, which would form a
continuous tract of land beyond it. Since writing the above, I have
seen Professor J. Forbes’s beautiful work on the glaciers of Norway: it
fully justifies a comparison of the Himalaya to Norway, which has long
been a familiar subject of theoretical enquiry with Dr. Thomson and
myself. The deep narrow valleys of Sikkim admirably represent the
Norwegian fiords; the lofty, rugged, snowy mountains, those more or
less submerged islands of the Norwegian coast; the broad rearward
watershed, or axis of the chain, with its lakes, is the same in both,
and the Yaru-tsampu occupies the relative position of the Baltic.
Along the whole chain of the Himalaya east of Kumaon there are, I have
no doubt, a succession of such lofty masses as Donkia, giving off
stupendous spurs such as that on which Kinchin forms so conspicuous a
feature. In support of this view we find every river rising far beyond
the snowy peaks, which are separated by continuously unsnowed ranges
placed between the great white masses that these spurs present to the
observer from the south.[405] From the Khasia mountains (south-east of
Sikkim) many of these groups or spurs were seen by Dr. Thomson and
myself, at various distances (80 to 210 miles); and these groups were
between the courses of the great rivers the Soobansiri, Monass, and
Pachoo, all east of Sikkim. Other masses seen from the Gangetic valley
probably thus mark the relative positions of the Arun, Cosi, Gunduk,
and Gogra rivers.
[405] At vol. i. p. 185, I have particularly called attention to the
fact, that west of Kinchinjunga there is no continuation of a snowy
Himalaya, as it is commonly called. So between Donkia and Chumulari
there is no perpetual snow, and the valley of the Machoo is very
broad, open, and comparatively flat.
Another mass like that of Chumulari and Donkia, is that around the
Mansarowar lakes, so ably surveyed by the brothers Captains R. and H.
Strachey, which is evidently the centre of the Himalaya. From it the
Gogra, Sutlej, Indus, and Yaru rivers all flow to the Indian side of
Asia; and from it spring four chains, two of which are better known
than the others. These are:—1. The eastern Himalaya, whose axis runs
north of Nepal, Sikkim, and Bhotan, to the bend of the Yaru, the valley
of which it divides from the plains of India. 2. The north-west
Himalaya, which separates the valley of the Indus from the plains of
India. Behind these, and probably parallel to them, lie two other
chains. 3. The Kouenlun or Karakoram chain, dividing the Indus from the
Yarkand river. 4. The chain north of the Yaru, of which nothing is
known. All the waters from the two first of these chains, flow into the
Indian Ocean, as do those from the south faces of the third and fourth;
those from the north side of the Kouenlun, and of the chain north of
the Yaru, flow into the great valley of Lake Lhop, which may once have
been continuous with the Amoor river.[406]
[406] The Chinese assert that Lake Lhop once drained into the
Hoang-ho; the statement is curious, and capable of confirmation when
central Asia shall have been explored.
For this view of the physical geography of the western Himalaya and
central Asia, I am indebted to Dr. Thomson. It is more consonant with
nature, and with what we know of the geography of the country and of
the nature of mountain chains, than that of the illustrious Humboldt,
who divides central Asia by four parallel chains, united by two
meridional ones; one at each extremity of the mountain district. It
follows in continuation and conclusion of our view that the mountain
mass of Pamir or Bolor, between the sources of the Oxus and those of
the Yarkand river, may be regarded as a centre from which spring the
three greatest mountain systems of Asia. These are:—1. A great chain,
which runs in a north-easterly direction as far as Behring’s Straits,
separating all the rivers of Siberia from those which flow into the
Pacific Ocean. 2. The Hindoo Koosh, continued through Persia, and
Armenia into Taurus. And, 3. The Muztagh or Karakorum, which probably
extends due east into China, south of the Hoang-ho, but which is broken
up north of Mansarowar into the chains which have been already
enumerated.
F.
ON THE CLIMATE OF SIKKIM.
The meteorology of Sikkim, as of every part of the Himalayan range, is
a subject of growing interest and importance; as it becomes yearly more
necessary for the Government to afford increased facilities for a
residence in the mountains to Europeans in search of health, or of a
salubrious climate for their families, or for themselves on retirement
from the exhausting service of the plains. I was therefore surprised to
find no further register of the weather at Dorjiling, than an
insufficient one of the rain-fall, kept by the medical officer in
charge of the station; who, in this, as in all similar cases,[407] has
neither the time nor the opportunity to give even the minimum of
required attention to the subject of meteorology. This defect has been
in a measure remedied by Dr. Chapman, who kept a twelve-months’
register in 1837, with instruments carefully compared with Calcutta
standards by the late James Prinsep, Esq., one of the most accomplished
men in literature and science that India ever saw.
[407] The government of India has gone to an immense expense, and
entailed a heavy duty upon its stationary medical officers, in
supplying them with sometimes admirable, but more often very
inaccurate, meteorological instruments, and requiring that daily
registers be made, and transmitted to Calcutta. In no case have I
found it to be in the officer’s power to carry out this object; he has
never time, seldom the necessary knowledge and experience, and far too
often no inclination. The majority of the observations are in most
cases left to personal native or other servants, and the laborious
results I have examined are too frequently worthless.
The annual means of temperature, rain-fall, etc., vary greatly in the
Himalaya; and apparently slight local causes produce such great
differences of temperature and humidity, that one year’s observations
taken at one spot, however full and accurate they may be, are
insufficient: this is remarkably the case in Sikkim, where the rainfall
is great, and where the difference between those of two consecutive
years is often greater than the whole annual London fall. My own
meteorological observations necessarily form but a broken series, but
they were made with the best instruments, and with a view to obtaining
results that should be comparable _inter se,_ and with those of
Calcutta; when away from Dorjiling too, in the interior of Sikkim, I
had the advantage of Mr. Muller’s services in taking observations at
hours agreed upon previous to my leaving, and these were of the
greatest importance, both for calculating elevations, and for
ascertaining the differences of temperature, humidity, diurnal
atmospheric tide, and rain-fall; all of which vary with the elevation,
and the distance from the plains of India.
Mr. Hodgson’s house proved a most favourable spot for an observatory,
being placed on the top of the Dorjiling spur, with its broad verandah
facing the north, in which I protected the instruments from
radiation[408] and wind. Broad grass-plots and a gravel walk surrounded
the house, and large trees were scattered about; on three sides the
ground sloped away, while to the north the spur gently rose behind.
[408] This is a most important point, generally wholly neglected in
India, where I have usually seen the thermometer hung in good shade,
but exposed to reflected heat from walls, gravel walks, or dry earth.
I am accustomed from experience to view all extreme temperatures with
great suspicion, on this and other accounts. It is very seldom that
the temperature of the free shaded air rises much above 100°, except
during hot winds, when the lower stratum only of atmosphere (often
loaded with hot particles of sand), sweeps over the surface of a soil
scorched by the direct rays of the sun.
Throughout the greater part of the year the prevailing wind is from the
south-east, and comes laden with moisture from the Bay of Bengal: it
rises at sunrise, and its vapours are early condensed on the forests of
Sinchul; billowy clouds rapidly succeed small patches of vapour, which
rolling over to the north side of the mountain, are carried north-west,
over a broad intervening valley, to Dorjiling. There they bank on the
east side of the spur, and this being partially clear of wood, the
accumulation is slow, and always first upon the clumps of trees. Very
generally by 9 a.m., the whole eastern sky, from the top of Dorjiling
ridge, is enveloped in a dense fog, while the whole western exposure
enjoys sunshine for an hour or two later. At 7 or 8 a.m., very small
patches are seen to collect on Tonglo, which gradually dilate and
coalesce, but do not shroud the mountain for some hours, generally not
before 11 a.m. or noon. Before that time, however, masses of mist have
been rolling over Dorjiling ridge to the westward, and gradually
filling up the valleys, so that by noon, or 1 p.m., every object is in
cloud. Towards sunset it falls calm, when the mist rises, first from
Sinchul, or if a south-east wind sets in, from Tonglo first.
The temperature is more uniform at Mr. Hodgson’s bungalow, which is on
the top of the Dorjiling ridge, than on either of its flanks; this is
very much because a good deal of wood is left upon it, whose cool
foliage attracts and condenses the mists. Its mean temperature is lower
by nearly 2·5° than that of Mr. Muller’s and Dr. Campbell’s houses,
both situated on the slopes, 400 feet below. This I ascertained by
numerous comparative observations of the temperature of the air, and by
burying thermometers in the earth: it is chiefly to be accounted for by
the more frequent sunshine at the lower stations, the power of the sun
often raising the thermometer in shade to 80°, at Mr. Muller’s; whereas
during the summer I spent at Mr. Hodgson’s it never rose much above
70°, attaining that height very seldom and for a very short period
only. The nights, again, are uniformly and equally cloudy at both
stations, so that there is no corresponding cold of nocturnal radiation
to reduce the temperature.
The mean decrease of temperature due to elevation, I have stated
(Appendix I.) to be about 1° for every 300 feet of ascent; according to
which law Mr. Hodgson’s should not be more than 1·5° colder than Mr.
Muller’s. These facts prove how difficult it is to choose
unexceptionable sites for meteorological observatories in mountainous
countries; discrepancies of so great an amount being due to local
causes, which, as in this case, are perhaps transient; for should the
top of the spur be wholly cleared of timber, its temperature would be
materially raised; at the expense, probably, of a deficiency of water
at certain seasons. Great inequalities of temperature are also produced
by ascending currents of heated air from the Great Rungeet valley,
which affect certain parts of the station only; and these raise the
thermometer 10° (even when the sun is clouded) above what it indicates
at other places of equal elevation.
The mean temperature of Dorjiling (elev. 7,430 feet) is very nearly
50°, or 2° higher than that of London, and 26° below that of Calcutta
(78°,[409] or 78·5° in the latest published tables[410]); which,
allowing 1° of diminution of temperature for every degree of latitude
leaves 1° due to every 300 feet of ascent above Calcutta to the height
of Dorjiling, agreeably to my own observations. This diminution is not
the same for greater heights, as I shall have occasion to show in a
separate chapter of this Appendix, on the decrement of heat with
elevation.
[409] Prinsep, in As. Soc. Journ., Jan. 1832, p. 30.
[410] Daniell’s Met. Essays, vol. ii. p. 341.
A remarkable uniformity of temperature prevails throughout the year at
Dorjiling, there being only 22° difference between the mean
temperatures of the hottest and coldest months; whilst in London, with
a lower mean temperature, the equivalent difference is 27°. At 11,000
feet this difference is equal to that of London. In more elevated
regions, it is still greater, the climate becoming excessive at 15,000
feet, where the difference amounts to 30° at least.[411] The
accompanying table is the result of an attempt to approximate to the
mean temperatures and ranges of the thermometer at various elevations.
[411] This is contrary to the conclusions of all meteorologists who
have studied the climate of the Alps, and is entirely due to the local
disturbances which I have so often dwelt upon, and principally to the
unequal distribution of moisture in the loftier rearward regions, and
the aridity of Tibet. Professor James Forbes states (Ed. Phil. Trans.,
v. xiv. p. 489):—1. That the decrement of temperature with altitude is
most rapid in summer: this (as I shall hereafter show) is not the case
in the Himalaya, chiefly because the warm south moist wind then
prevails. 2. That the annual range of temperature diminishes with the
elevation: this, too, is not the case in Sikkim, because of the barer
surface and more cloudless skies of the rearward loftier regions. 3.
That the diurnal range of temperature diminishes with the height: that
this is not the cane follows from the same cause. 4. That radiation is
least in winter: this is negatived by the influence of the summer
rains.
Altitude Mean
Shade Mean
Warmest
Month Mean
Coldest
Month Mean Daily
Range of
Temperature Rain-fall
in
inches 11,000 feet
15,000 feet
19,000 feet 40·9
29·8
19·8 50·0
40·0
32·0 24·0
11·0
0·0 20·0
27·0
35·0 40·0
20·0
10·0 1°=320 feet
1°=350 feet
1°=400 feet
Supposing the same formula to apply (which I exceedingly doubt) to
heights above 19,000 feet, 2° would be the mean annual temperature of
the summit of Kinchinjunga, altitude 28,178 feet, the loftiest known
spot on the globe: this is a degree or two higher than the temperature
of the poles of greatest cold on the earth’s surface, and about the
temperature of Spitzbergen and Melville island.
The upper limit of phenogamic vegetation coincides with a mean
temperature of 30° on the south flank of Kinchinjunga, and of 22° in
Tibet; in both cases annuals and perennial-rooted herbaceous plants are
to be found at elevations corresponding to these mean temperatures, and
often at higher elevations in sheltered localities. I have assumed the
decrease of temperature for a corresponding amount of elevation to be
gradually less in ascending (1°=320 feet at 6000 to 10,000 feet, 1°=400
feet at 14,000 to 18,000 feet). My observations appear to prove this,
but I do not regard them as conclusive; supposing them to be so, I
attribute it to a combination of various causes, especially to the
increased elevation and yet unsnowed condition of the mass of land
elevated above 16,000 feet, and consequent radiation of heat; also to
the greater amount of sunshine there; and to the less dense mists which
obstruct the sun’s rays at all elevations. In corroboration of this I
may mention that the decrease of temperature with elevation is much
less in summer than in winter, 1° of Fahr. being equivalent to only 250
feet in January between 7000 and 13,000 feet, and to upwards of 400
feet in July. Again, at Dorjiling (7,430 feet) the temperature hardly
ever rises above 70° in the summer months, yet it often rises even
higher in Tibet at 12,000 to 14,000 feet. On the other hand, the
winters, and the winter nights especially, are disproportionately cold
at great heights, the thermometer falling upwards of 40° below the
Dorjiling temperature at an elevation only 6000 feet higher.
The diurnal distribution of temperature is equally and similarly
affected by the presence of vapour at different altitudes. The lower
and outer ranges of 6000 to 10,000 feet, first receive the diurnal
charge of vapour-loaded southerly winds; those beyond them get more of
the sun’s rays, and the rearward ones more still. Though the summer
days of the northern localities are warmer than their elevation would
indicate, the nights are not proportionally cold; for the light mist of
14,000 feet, which replaces the dense fog of 7000 feet, effectually
obstructs nocturnal radiation, though it is less an obstacle to solar
radiation. Clear nights, be it observed, are as rare at Momay (15,300
feet) as at Dorjiling, the nights if windy being rainy; or, if calm,
cold currents descend from the mountains, condensing the moist vapours
of the valleys, whose narrow floors are at sunrise bathed in mist at
all elevations in Sikkim. The rise and dispersion of these dense mists,
and their collection and recondensation on the mountains in the
morning, is one of the most magnificent phenomena of the Himalaya, when
viewed from a proper elevation; it commences as soon as the sun appears
on the horizon.
The mean daily range of the thermometer at 7000 feet is 13° in cleared
spots, but considerably less in wooded, and certainly one-third less in
the forest itself. At Calcutta, which has almost an insular climate, it
amounts to 17°; at Delhi, which has a continental one, to 24·6°; and in
London to 17·5°. At 11,000 feet it amounts to about 20°, and at 15,000
feet to 27°. These values vary widely in the different months, being
much less in the summer or rainy months. The following is probably a
fair approximation:—
At 7,000 feet it amounts to 8–9° in Aug. and Sept., and 17° in Dec.
At 11,000 feet it amounts to 12° in Aug. and Sept., and 30° in Dec.
At 15,000 feet it amounts to 15° in Aug. and Sept., and 40° in Dec.
At London it amounts to 20° in Aug. and Sept., and 10° in Dec.
The distribution of temperature throughout the day and year varies less
at Dorjiling than in most mountainous countries, owing to the
prevailing moisture, the effect of which is analogous to that of a
circumambient ocean to an island: the difference being, that in the
case of the island the bulk of water maintains an uniform temperature;
in that of Dorjiling the quantity of vapour acts directly by
interfering with terrestrial and solar-radiation, and indirectly by
nurturing a luxuriant vegetation. The result in the latter case is a
climate remarkable for its equability, and similar in many features to
that of New Zealand, South-west Chili, Fuegia, and the damp west coasts
of Scotland and Ireland, and other countries exposed to moist sea
winds.
The mean temperature of the year at Dorjiling, as taken by maxima and
minima thermometers[412] by Dr. Chapman, is nearly the same as that of
March and October: January, the coldest month, is more than 13·4°
colder than the mean of the year; but the hottest month is only 8·3°
warmer than the same mean: at Calcutta the months vary less from the
mean; at Delhi more; and in London the distribution is wholly
different; there being no rains to modify the summer heat, July is 13°
hotter, and January 14° colder than the mean of the year.
[412] The mean of several of the months, thus deduced, often varies a
good deal from the truth, owing to the unequal diurnal distribution of
heat; a very few minutes’ sunshine raises the temperature l0° or 15°
above the mean of the day; which excessive heat (usually transient)
the maximum thermometer registers, and consequently gives too high a
mean.
This distribution of the seasons has a most important effect upon
vegetation, to which sufficient attention has not been paid by
cultivators of alpine Indian plants; in the first place, though English
winters are cold enough for such, the summers are too hot and dry; and,
in the second place, the great accession of temperature, causing the
buds to burst in spring, occurs in the Himalaya in March, when the
temperature at 7000 feet rises 8° above that of February, raising the
radiating thermometer always above the freezing point, whence the young
leaves are never injured by night frost: in England the corresponding
rise is only 3°, and there is no such accession of temperature till
May, which is 8° warmer than April; hence, the young foliage of many
Himalayan plants is cut off by night frosts in English gardens early in
the season, of which _Abies Webbiana_ is a conspicuous example.
The greatest heat of the day occurs at Dorjiling about noon, owing to
the prevalent cloud, especially during the rainy months, when the sun
shines only in the mornings, if at all, and the clouds accumulate as
the day advances. According to hourly observations of my own, it
occurred in July at noon, in August at 1 p.m., and in September (the
most rainy month) there was only four-tenths of a degree difference
between the means of noon, 1 p.m., and 2 p.m., but I must refer to the
abstracts at the end of this chapter for evidence of this, and of the
wonderful uniformity of temperature during the rainy months. In the
drier season again, after September, the greatest heat occurs between 2
and 3 p.m.; in Calcutta the hottest hour is about 2.45 p.m., throughout
the year; and in England also about 3 p.m.
The hour whose temperature coincides with the mean of the day
necessarily varies with the distribution of cloud and sunshine; it is
usually about 7 a.m. and 7 p.m.; whereas in Calcutta the same
coincidence occurs at a little before 10 a.m., and in England at about
8 a.m.
Next to the temperature of the air, observations on that of the earth
are perhaps of the greatest value; both from their application to
horticulture, and from the approximation they afford to the mean
temperature of the week or month in which they are taken. These form
the subject of a separate chapter.
Nocturnal and solar radiation, the one causing the formation of dew and
hoar-frost when the air in the shade is above freezing, end killing
plants by the rapid abstraction of heat from all their surfaces which
are exposed to the clear sky, and the other scorching the skin and
tender plants during the day, are now familiar phenomena, and
particularly engaged my attention during my whole Indian journey. Two
phenomena particularly obstruct radiation in Sikkim—the clouds and fog
from the end of May till October, and the haze from February till May.
Two months alone are usually clear; one before and one after the rains,
when the air, though still humid, is transparent. The haze has never
been fully explained, though a well-known phenomenon. On the plains of
India, at the foot of the hills, it begins generally in the forenoon of
the cold season, with the rise of the west wind; and, in February
especially, obscures the sun’s disc by noon; frequently it lasts
throughout the twenty-four hours, and is usually accompanied by great
dryness of the atmosphere. It gradually diminishes in ascending, and
have never experienced it at 10,000 feet; at 7000, however, it very
often, in April, obscures the snowy ranges 30 miles off, which are
bright and defined at sunrise, and either pale away, or become of a
lurid yellow-red, according to the density of this haze, till they
disappear at 10 a.m. I believe it always accompanies a south-west wind
(which is a deflected current of the north-west) and dry atmosphere in
Sikkim.
The observations for solar radiation were taken with a black-bulb
thermometer, and also with actinometers, but the value of the data
afforded by the latter not being fixed or comparative, I shall give the
results in a separate section. (See Appendix K.) From a multitude of
desultory observations, I conclude that at 7,400 feet, 125·7°, or +67°
above the temperature of the air, is the average maximum effect of the
sun’s rays on a black-bulb thermometer[413] throughout the year,
amounting rarely to +70° and +80° in the summer months, but more
frequently in the winter or spring. These results, though greatly above
what are obtained at Calcutta, are not much, if at all, above what may
be observed on the plains of India. This effect is much increased with
the elevation. At 10,000 feet in December, at 9 a.m., I saw the mercury
mount to 132° with a difl: of +94°, whilst the temperature of shaded
snow hard by was 22°; at 13,100 feet, in January, at 9 a.m., it has
stood at 98°, diff. +68·2°; and at 10 a.m., at 114°, diff. +81·4°,
whilst the radiating thermometer on the snow had fallen at sunrise to
0·7°. In December, at 13,500 feet, I have seen it 110°, diff. +84°; at
11 a.m., 11,500 feet; 122°, diff: +82°. This is but a small selection
from many instances of the extraordinary power of solar radiation in
the coldest months, at great elevations.
[413] From the mean of very many observations, I find that 10° is the
average difference at the level of the sea, in India, between two
similar thermometers, with spherical bulbs (half-inch diam.), the one
of black, and the other of plain glass, and both being equally exposed
to the sun’s rays.
Nocturnal and terrestrial radiation are even more difficult phenomena
for the traveller to estimate than solar radiation, the danger of
exposing instruments at night being always great in wild countries. I
most frequently used a thermometer graduated on the glass, and placed
in the focus of a parabolic reflector, and a similar one laid upon
white cotton,[414] and found no material difference in the mean of many
observations of each, though often 1° to 2° in individual ones.
Avoiding radiation from surrounding objects is very difficult,
especially in wooded countries. I have also tried the radiating power
of grass and the earth; the temperature of the latter is generally
less, and that of the former greater, than the thermometer exposed on
cotton or in the reflector, but much depends on the surface of the
herbage and soil.
[414] Snow radiates the most powerfully of any substance I have tried;
in one instance, at 13,000 feet, in January, the thermometer on snow
fell to 0·2°, which was 10·8° below the temperature at the time, the
grass showing 6·7°; and on another occasion to 1·2°, when the air at
the time (before sunrise) was 21·2°; the difference therefore being
20°. I have frequently made this observation, and always with a
similar result; it may account for the great injury plants sustain
from a thin covering of ice on their foliage, even when the
temperature is but little below the freezing-point.
The power of terrestrial, like that of solar radiation, increases with
the elevation, but not in an equal proportion. At 7,400 feet, the mean
of all my observations shows a temperature of 35·4°. During the rains,
3° to 4° is the mean maximum, but the nights being almost invariably
cloudy, it is scarcely on one night out of six that there is any
radiation. From October to December the amount is greater=10° to 12,
and from January till May greater still, being as much as 15°. During
the winter months the effect of radiation is often felt throughout the
clear days, dew forming abundantly at 4000 to 8000 feet in the shaded
bottoms of narrow valleys, into which the sun does not penetrate till
10 a.m., and from which it disappears at 3 p.m. I have seen the
thermometer in the reflector fall 12° at 10 a.m. in a shaded valley.
This often produces an anomalous effect, causing the temperature in the
shade to fall after sunrise; for the mists which condense in the bottom
of the valleys after midnight disperse after sunrise, but long before
reached by the sun, and powerful radiation ensues, lowering the
surrounding temperature: a fall of 1° to 2° after sunrise of air in the
shade is hence common in valleys in November and December.[415] The
excessive radiation of the winter months often gives rise to a curious
phenomenon; it causes the formation of copious dew on the blanket of
the traveller’s bed, which radiates heat to the tent roof, and this
inside either an open or a closed tent. I have experienced this at
various elevations, from 6000 to 16,000 feet. Whether the minimum
temperature be as high as 50°, or but little above zero, the effect is
the same, except that hoar-frost or ice forms in the latter case.
Another remarkable effect of nocturnal radiation is the curl of the
alpine rhododendron leaves in November, which is probably due to the
freezing and consequent expansion of the water in the upper strata of
cells exposed to the sky. The first curl is generally repaired by the
ensuing day’s sun, but after two or three nights the leaves become
permanently curled, and remain so till they fall in the following
spring.
[415] Such is the explanation which I have offered of this phenomenon
in the Hort. Soc. Journal. On thinking over the matter since, I have
speculated upon the probability of this fall of temperature being due
to the absorption of heat that must become latent on the dispersion of
the dense masses of white fog that choke the valleys at sunrise.
I have said that the nocturnal radiation in the English spring months
is the great obstacle to the cultivation of many Himalayan plants; but
it is not therefore to be inferred that there is no similar amount of
radiation in the Himalaya; for, on the contrary, in April its amount is
much greater than in England, frequently equalling 13° of difference;
and I have seen 16° at 7,500 feet; but the minimum temperature at the
time is 51°, and the absolute amount of cold therefore immaterial. The
mean minimum of London is 38°, and, when lowered 5·5° by radiation, the
consequent cold is very considerable. Mr. Daniell, in his admirable
essay on the climate of London, mentions 17° as the maximum effect of
nocturnal radiation ever observed by him. I have registered 16° in
April at Dorjiling; nearly as much at 6000 feet in February; twice 13°,
and once 14·2° in September at 15,500 feet; and 10° in October at
16,800 feet; nearly 13° in January at 7000 feet; 14·5° in February at
that elevation, and, on several occasions, 14·7° at 10,000 feet in
November.
The annual rain-fall at Dorjiling averages 120 inches (or 10 feet), but
varies from 100 to 130 in different years; this is fully three times
the amount of the average English fall,[416] and yet not one-fourth of
what is experienced on the Khasia hills in Eastern Bengal, where fifty
feet of rain falls. The greater proportion descends between June and
September, as much as thirty inches sometimes falling in one month.
From November to February inclusive, the months are comparatively dry;
March and October are characterised by violent storms at the equinoxes,
with thunder, destructive lightning, and hail.
[416] The general ideas on the subject of the English rain-fall are so
very vague, that I may be pardoned for reminding my readers that in
1852, the year of extraordinary rain, the amounts varied from 28·5
inches in Essex, to 50 inches at Cirencester, and 67·5 (average of
five years) at Plympton St. Mary’s, and 102·5 at Holme, on the Dart.
The rain-gauge takes no account of the enormous deposition from mists
and fogs: these keep the atmosphere in a state of moisture, the amount
of which I have estimated at 0·88 as the saturation-point at Dorjiling,
0·83 being that of London. In July, the dampest month, the
saturation-point is 0·97; and in December, owing to the dryness of the
air on the neighbouring plains of India, whence dry blasts pass over
Sikkim, the mean saturation-point of the month sometimes falls as low
as 0·69.
The dew-point is on the average of the year 49·3°, or 3° below the mean
temperature of the air. In the dampest month (July) the mean dew-point
is only eight-tenths of a degree below the temperature, whilst in
December it sinks 10° below it. In London the dew-point is on the
average 5·6° below the temperature; none of the English months are so
wet as those of Sikkim, but none are so dry as the Sikkim December
sometimes is.
_On the weight of the atmosphere in Sikkim; and its effects on the
human frame._
Of all the phenomena of climate, the weight of the atmosphere is the
most remarkable for its elusion of direct observation, when unaided by
instruments. At the level of the sea, a man of ordinary bulk and
stature is pressed upon by a superincumbent weight of 30,000 pounds or
13·5 tons. An inch fall or rise in the barometer shows that this load
is lightened or increased, sometimes in a few hours, by nearly 1,000
pounds; and no notice is taken of it, except by the meteorologist, or
by the speculative physician, seeking the subtle causes of epidemic and
endemic complaints. At Dorjiling (7,400 feet), this load is reduced to
less than 2,500 pounds, with no appreciable result whatever on the
frame, however suddenly it be transported to that elevation. And the
observation of my own habits convinced me that I took the same amount
of meat, drink, sleep, exercise and work, not only without
inconvenience, but without the slightest perception of my altered
circumstances. On ascending to 14,000 feet, owing to the diminished
supply of oxygen, exercise brings on vertigo and headache; ascending
higher still, lassitude and tension across the forehead ensue, with
retching, and a sense of weight dragging down the stomach, probably due
to dilatation of the air contained in that organ. Such are the all but
invariable effects of high elevations; varying with most persons
according to the suddenness and steepness of the ascent, the amount and
duration of exertion, and the length of time previously passed at great
heights. After having lived for some weeks at 15,300 feet, I have
thence ascended several times to 18,500, and once above 19,000 feet,
without any sensations but lassitude and quickness of pulse;[417] but
in these instances it required great caution to avoid painful symptoms.
Residing at 15,300 feet, however, my functions were wholly undisturbed;
nor could I detect any quickness of pulse or of respiration when the
body was at rest, below 17,000 feet. At that elevation, after resting a
party of eight men for an hour, the average of their and my pulses was
above 100°, both before and after eating; in one case it was 120°, in
none below 80°.
[417] I have in a note to vol. ii. p. 160, stated that I never
experienced in my own person, nor saw in others, bleeding at the ears,
nose, lips, or eyelids.
Not only is the frame of a transient visitor unaffected (when at rest)
by the pressure being reduced from 30,000 to 13,000 pounds, but the
Tibetan, born and constantly residing at upwards of 14,000 feet,
differs in no respect that can be attributed to diminished pressure,
from the native of the level of the sea. The averaged duration of life,
and the amount of food and exercise is the same; eighty years are
rarely reached by either. The Tibetan too, however inured to cold and
great elevations, still suffers when he crosses passes 18,000 or 19,000
feet high, and apparently neither more nor less than I did.
Liebig remarks (in his “Animal Chemistry”) that in an equal number of
respirations,[418] we consume a larger amount of oxygen at the level of
the sea than on a mountain; and it can be shown that under ordinary
circumstances at Dorjiling, 20·14 per cent. less is inhaled than on the
plains of India. Yet the chest cannot expand so as to inspire more at
once, nor is the respiration appreciably quickened; by either of which
means nature would be enabled to make up the deficiency. It is true
that it is difficult to count one’s own respirations, but the average
is considered in a healthy man to be eighteen in a minute; in my own
case it is sixteen, an acceleration of which by three or four could not
have been overlooked, in the repeated trials I made at Dorjiling, and
still less the eight additional inhalations required at 15,000 feet to
make up for the deficiency of oxygen in the air of that elevation.
[418] For the following note I am indebted to my friend, C. Muller,
Esq., of Patna.—
According to Sir H. Davy, a man consumes 45,504 cubic inches of
oxygen in twenty-four hours, necessitating the inspiration of
147,520 cubic inches of atmospheric air.—At pressure 23 inches, and
temp. 60° this volume of atmospheric air (dry) would weigh
35,138·75 grains.—At pressure 30 in., temp. 80°, it would weigh
43,997·63 gr.
The amount of oxygen in atmospheric air is 23·32 per cent. by
weight. The oxygen, then, in 147,520 cubic inches of dry air, at
pressure 23 in., temp. 80°, weighs 8,194·35 gr.; and at pressure 30
in., temp. 80°, it weighs 10,260·25 gr.
Hence the absolute quantity of oxygen in a given volume of
atmospheric air, when the pressure is 23 in., and the temp. 60°, is
20·14 per cent. less than when the pressure is 30 in. and the temp.
80°.
When the air at pressure 23 in:, temp. 60°, is saturated with
moisture, the proportion of dry air and aqueous vapour in 100 cubic
inches is as follows:—
Dry air 97·173
Vapour 2·827
At pressure 30 in., temp. 80°, the proportions are:—
Dry air 96·133
Vapour 3·867
The effect of aqueous vapour in the air on the amount of oxygen
available for consumption, is very trifling; and it must not be
forgotten that aqueous vapour supplies oxygen to the system as well
as atmospheric air.
It has long been surmised that an alpine vegetation may owe some of its
peculiarities to the diminished atmospheric pressure; and that the
latter being a condition which the gardener cannot supply, he can never
successfully cultivate such plants in general. I know of no foundation
for this hypothesis; many plants, natives of the level of the sea in
other parts of the world, and some even of the hot plains of Bengal,
ascend to 12,000 and even 15,000 feet on the Himalaya, unaffected by
the diminished pressure. Any number of species from low countries may
be cultivated, and some have been for ages, at 10,000 to 14,000 feet
without change. It is the same with the lower animals; innumerable
instances may with ease be adduced of pressure alone inducing no
appreciable change, whilst there is absence of proof to the contrary.
The phenomena that accompany diminished pressure are the real obstacles
to the cultivation of alpine plants, of which cold and the excessive
climate are perhaps the most formidable. Plants that grow in localities
marked by sudden extremes of heat and cold, are always very variable in
stature, habit, and foliage. In a state of nature we say the plants
“accommodate themselves” to these changes, and so they do within
certain limits; but for one that survives of all the seeds that
germinate in these inhospitable localities, thousands die. In our
gardens we can neither imitate the conditions of an alpine climate, nor
offer others suited to the plants of such climates.
The mean height of the barometer at Mr. Hodgson’s was 23·010, but
varied 0·161 between July, when it was lowest, and October, when it was
highest; following the monthly rise and fall of Calcutta as to period,
but not as to amount (or amplitude); for the mercury at Calcutta stands
in July upwards of half an inch (0·555 Prinsep) lower than it does in
December.
The diurnal tide of atmosphere is as constant as to the time of its ebb
and flow at Dorjiling as at Calcutta; and a number of very careful
observations (made with special reference to this object) between the
level of the plains of India, and 17,000 feet, would indicate that
there is no very material deviation from this at any elevation in
Sikkim. These times are very nearly 9.50 a.m. and about 10 p.m. for the
maxima, the 9.50 a.m. very constantly, and the 10 p.m. with more
uncertainty; and 4 a.m. and 4 p.m. for the minima, the afternoon ebb
being most true to its time, except during the rains.
At 9.50 a.m. the barometer is at its highest, and falls till 4 p.m.,
when it stands on the average of the year 0·074 of an inch lower;
during the same period the Calcutta fall is upwards of one-tenth of an
inch (0·121 Prinsep).
It has been proved that at considerable elevations in Europe, the hours
of periodic ebb and flow differ materially from those which prevail at
the level of the sea; but this is certainly not the case in the Sikkim
Himalaya.
The amplitude decreases in amount from 0·100 at the foot of the hills,
to 0·074 at 7000 feet; and the mean of 132 selected unexceptionable
observations, taken at nine stations between 8000 and 15,500 feet, at
9.50 a.m. and 4 p.m., gives an average fall of 0·056 of an inch; a
result which is confirmed by interpolation from numerous horary
observations at these and many other elevations, where I could observe
at the critical hours.
That the Calcutta amplitude is not exceptionally great, is shewn by the
register kept at different places in the Gangetic valley and plains of
India, between Saharunpore and the Bay of Bengal. I have seen
apparently trustworthy records of seven[419] such, and find that in all
it amounts to between 0·084 and 0·120 inch, the mean of the whole being
0·101 of an inch.
[419] Calcutta, Berampore, Benares, Nagpore, Moozufferpore, Delhi, and
Saharunpore.
The amplitude is greatest (0·088) in the spring months (March, April,
and May), both at Dorjiling and Calcutta: it is least at both in June
and July, (0·027 at Dorjiling), and rises again in autumn (to ·082 in
September).
The horary oscillations also are as remarkably uniform at all
elevations, as the period of ebb and flow: the mercury falls slowly
from 9.50 a.m. (when it is at its highest) till noon, then rapidly till
3 p.m., and slowly again till 4 p.m.; after which there is little
change until sunset; it rises rapidly between 7 and 9 p.m., and a
little more till 10 p.m.; thence till 4 a.m. the fall is
inconsiderable, and the great rise occurs between 7 and 9 a.m.
It is well known that these fluctuations of the barometer are due to
the expansion and contraction by heat and moisture of the column of
atmosphere that presses on the mercury, in the cistern of the
instrument: were the air dry, the effect would be a single rise and
fall;[420] the barometer would stand highest at the hottest of the
twenty-four hours, and lowest at the coldest; and such is the case in
arid continental regions which are perennially dry. That such would
also be the case at Calcutta and throughout the Himalaya of Sikkim, is
theoretically self-evident, and proved by my horary observations taken
during the rainy months of 1848. An inspection of these at the end of
this section (where a column contains the pressure of dry air) shows
but one maximum of pressure, which occurs at the coldest time of the
twenty-four hours (early in the morning), and one minimum in the
afternoon. In the table of mean temperatures of the months, also
appended to this section, will also be found a column allowing the
pressure of dry air, whence it will be seen that there is but one
maximum of the pressure of dry air, occurring at the coldest season in
December, and one minimum, in July. The effect of the vapour is the
same on the annual as upon the diurnal march of the pressure, producing
a double maximum and minimum in the year in one case, and in the
twenty-four hours in the other.
[420] This law, for which we are indebted to Professor Dove, has been
clearly explained by Colonel Sabine in the appendix to his translation
of Humboldt’s “Cosmos,” vol. i. p. 457.
I append a meteorological register of the separate months, but at the
same time must remind the reader that it does not pretend to strict
accuracy. It is founded upon observations made at Dorjiling by Dr.
Chapman in the year 1837, for pressure temperature and wet-bulb only;
the other data and some modifications of the above are supplied from
observations of my own. Those for terrestrial and nocturnal radiation
are accurate as far as they go, that is to say, they are absolute
temperatures taken by myself, which may, I believe, be recorded in any
year, but much higher are no doubt often to be obtained. The dew-points
and saturations are generally calculated from the mean of two day
observations (10 a.m. and 4 p.m.) of the wet-bulb thermometer, together
with the minimum, or are taken from observations of Daniell’s
hygrometer; and as I find the mean of the temperature of 10 a.m., 4
p.m., and the minimum, to coincide within a few tenths with the mean
temperature of the whole day, I assume that the mean of the wet-bulb
observations of the same hours will give a near approach to that of the
twenty-four hours. The climate of Dorjiling station has been in some
degree altered by extensive clearances of forest, which render it more
variable, more exposed to night frosts and strong sun-heat, and to
drought, the drying up of small streams being one direct consequence.
My own observations were taken at Mr. Hodgson’s house, elevated 7,430
feet, the position of which I have indicated at the commencement of
this section, where the differences of climate due to local causes are
sufficiently indicated to show that in no two spots could similar
meteorological results be obtained. At Mr. Hodgson’s, for instance, the
uniformity of temperature and humidity is infinitely more remarkable
than at Dr. Chapman’s, possibly from my guarding more effectually
against radiation, and from the greater forests about Mr. Hodgson’s
house. I have not, however, ventured to interfere with the temperature
columns on this account.
DORJILING METEOROLOGICAL REGISTER.
Jan. Feb. Mar. Apr. May June Pressure of
Atmosphere[421]
Range of Pressure
Mean Shade
Maximum Shade
Maximum Sun
Greatest Difference
Mean Maximum Shade
Minimum Shade
Minimum Radiation
Greatest Difference
Mean Minimum Shade
Mean Daily Range of Temps
Sunk Thermometer
Mean Dew-point
Mean Dryness
Force of Vapour
Pressure of Dry Air
Mean Saturation
Rain in inches 23·307
·072
40·0
56·0
119·0
72·0
47·2
29·0
16·0
12·7
32·8
14·4
46·0
34·3
5·1
·216
23·091
·84
1·72 23·305
·061
42·1
57·0
124·0
78·0
50·0
25·5
23·0
15·3
34·2
15·8
48·0
37·2
3·9
·239
23·066
·87
0·92 23·307
·083
50·7
66·5
120·0
60·0
58·4
37·0
27·8
8·7
43·1
15·3
50·0
45·8
5·8
·323
23·084
·82
1·12 23·280
·085
55·9
68·5
125·0
66·0
63·7
38·0
33·0
16·0
48·1
15·6
58·0
49·8
6·6
·371
22·909
·80
2·52 23·259
·088
57·6
69·0
125·0
65·0
65·3
38·0
40·0
10·0
50·0
15·3
61·0
54·4
2·7
·434
22·825
·91
9·25 23·207
·067
61·2
71·0
126·2
62·2
66·7
51·5
47·0
4·8
55·8
10·9
62·0
59·5
2·0
·515
22·692
·93
26·96
July Aug. Sept. Oct. Nov. Dec. Mean Pressure of
Atmosphere[421]
Range of Pressure
Mean Shade
Maximum Shade
Maximum Sun
Greatest Difference
Mean Maximum Shade
Minimum Shade
Minimum Radiation
Greatest Difference
Mean Minimum Shade
Mean Daily Range of Temps
Sunk Thermometer
Mean Dew-point
Mean Dryness
Force of Vapour
Pressure of Dry Air
Mean Saturation
Rain in inches 23·203
·062
61·4
69·5
130·0
62·0
65·5
56·0
52·0
3·5
57·3
8·2
62·2
60·7
0·8
·535
22·668
·97
25·34 23·230
·070
61·7
70·0
133·0
62·0
66·1
54·5
50·0
3·5
57·4
8·7
62·0
60·4
1·1
·530
22·700
·96
29·45 23·300
·082
59·9
70·0
142·0
70·0
64·7
51·5
47·5
10·0
55·2
9·5
61·0
58·5
1·4
·498
22·802
·95
15·76 23·372
·075
58·0
68·0
133·0
65·0
66·5
43·5
32·0
12·0
49·5
17·0
60·0
52·5
4·2
·407
22·865
·86
8·66 23·330
·078
50·0
63·0
123·0
68·0
56·5
38·0
30·0
12·0
43·5
13·0
55·0
46·5
3·2
·331
22·999
·90
0·11 23·365
·062
43·0
56·0
108·0
77·2
51·6
32·5
26·0
10·0
34·9
16·7
49·0
31·8
10·6
·198
23·165
·69
0·45 22·289
·074
53·5
65·4
125·7
67·3
60·2
41·3
35·4
9·9
46·8
13·4
56·2
49·4
4·0
·383
22·906
·88
Sum
122·26
[421]
These are taken from Dr. Chapman’s Table; and present a greater annual
range (=0·169) than my observations in 1848–9, taken at Mr. Hodgson’s
which is higher than Dr. Chapman’s; or than Mr. Muller’s, which is a
little lower, and very near it.
_Horary Observations at Jillapahar, Dorjiling, Alt. 7,430 feet._
JULY, 1848
No. of
Obser-
vations Hour Baro-
meter
corrected Temp.
Air Dew
Point Diff. Tension
of
Vapour Weight
of
Vapour Humi-
dity Pressure
of
Dry Air 7
23
27
22
20
26
12
11
25
23
13
10
6
6
22
6
6
19 1 a.m.
8
9
10
11
Noon
1 p.m.
2
3
4
5
6
7
8
9
10
11
Midnight 22·877
·882
·884
+·899
·899
·884
·876
·866
·852
·846
–·840
·845
·853
·867
·878
·885
+·887
·887 59·6
62·1
62·6
63·5
64·1
65·0
64·1
64·4
64·8
64·1
64·7
63·7
62·7
61·0
60·7
60·5
60·2
59·8 58·9
60·6
61·3
61·7
62·3
63·1
61·7
61·0
62·6
61·7
64·0
61·5
61·1
59·5
59·4
59·5
59·2
59·1 0·7
1·5
1·3
1·8
1·8
1·9
2·4
3·4
2·2
2·4
0·7
2·2
1·6
1·5
1·3
1·0
1·0
0·7 ·504
·534
·546
·554
·565
·580
·566
·541
·571
·554
·597
·549
·542
·515
·512
·514
·508
·507 5·65
6·03
6·10
6·12
6·27
6·44
6·13
6·00
6·32
6·13
6·62
6·12
6·03
5·74
5·72
5·75
5·70
5·68 ·988
·950
·960
·945
·945
·940
·923
·892
·930
·924
·978
·928
·948
·952
·960
·968
·965
·975 22·373
·348
·338
·345
·334
·304
·310
·325
·281
·292
–·243
·296
·311
·352
·366
·371
·379
+·382
AUGUST
No. of
Obser-
vations Hour Baro-
meter
corrected Temp.
Air Dew
Point Diff. Tension
of
Vapour Weight
of
Vapour Humi-
dity Pressure
of
Dry Air 15
26
28
28
24
23
21
21
21
19
19
19
19
19
19
19
19
19 1 a.m.
8
9
10
11
Noon
1 p.m.
2
3
4
5
6
7
8
9
10
11
Midnight 22·909
·904
·915
+·917
·915
·905
·898
·884
·873
·855
–·853
·863
·865
·878
·890
+·893
·892
·889 59·8
62·1
63·1
64·3
64·7
64·7
65·3
65·0
64·8
63·9
63·2
62·3
61·6
61·1
60·7
60·3
60·1
60·0 59·5
61·5
61·9
62·7
63·1
63·4
63·3
63·4
63·1
62·4
61·7
60·8
60·4
60·2
60·0
59·7
59·7
59·4 0·3
0·6
1·2
1·6
1·6
1·3
2·0
1·6
1·7
1·5
1·5
1·5
1·2
0·9
0·7
0·6
0·4
0·6 ·514
·549
·558
·572
·580
·586
·584
·586
·579
·568
·554
·538
·531
·527
·523
·518
·517
·513 5·70
6·13
6·20
6·35
6·42
6·50
6·48
6·50
6·43
6·30
6·15
6·00
5·92
5·88
5·85
5·78
5·79
5·73 ·992
·980
·962
·950
·948
·958
·940
·950
·943
·952
·952
·952
·962
·970
·976
·980
·988
·980 +22·395
·355
·357
·345
·335
·319
·314
·298
·294
–·287
·299
·325
·334
·351
·367
·375
·375
·376
SEPTEMBER
No. of
Obser-
vations Hour Baro-
meter
corrected Temp.
Air Dew
Point Diff. Tension
of
Vapour Weight
of
Vapour Humi-
dity Pressure
of
Dry Air 28
29
28
24
23
23
23
23
23
19
19
20
21
22
24
24
23 8 a.m.
9
10
11
Noon
1 p.m.
2
3
4
5
6
7
8
9
10
11
Midnight 23·000
·013
+·018
·009
22·995
·980
·962
·947
–·944
·944
·948
·958
·975
·986
+·991
·989
·994 59·2
60·1
60·8
61·6
62·4
62·7
62·8
62·3
61·8
60·3
59·4
58·7
58·2
57·8
57·4
57·0
56·7 58·1
58·5
59·5
60·0
60·5
60·5
60·4
60·0
59·9
58·6
58·4
57·4
57·0
56·6
56·4
55·9
55·4 1·1
1·6
1·3
1·6
1·9
2·2
2·4
2·3
1·9
1·7
1·0
1·3
1·2
1·2
1·0
1·1
1·3 ·492
·497
·514
·523
·533
·532
·531
·522
·521
·498
·496
·479
·473
·467
·463
·456
·449 5·50
5·57
5·77
5·83
5·93
5·92
5·90
5·83
5·82
5·58
5·58
5·60
5·33
5·25
5·23
5·15
5·07 ·968
·945
·958
·950
·942
·942
·925
·924
·940
·940
·968
·960
·962
·960
·968
·962
·927 22·508
·526
·504
·506
·462
·448
·431
·425
–·423
·446
·452
·479
·502
·519
·528
·533
+·545
OCTOBER (22 days)
No. of
Obser-
vations Hour Baro-
meter
corrected Temp.
Air Dew
Point Diff. Tension
of
Vapour Weight
of
Vapour Humi-
dity Pressure
of
Dry Air 11
19
20
20
19
13
15
13
13
14
16
13
6
7
3
7
14
18
14 6-6.30
7 a.m.
8
9
10
11
Noon
1 p.m.
2
3
4
5
6
7
8
9
10
11
Midnight 23·066
·072
·086
·099
+·100
·079
·072
·055
·033
·027
·024
–·022
·033
·045
·038
·061
+·072
·067
·068 54·4
54·3
55·2
56·3
57·1
57·6
57·9
58·0
57·7
57·9
57·9
56·6
55·9
55·4
53·7
55·1
54·6
54·5
54·1 52·7
52·3
53·7
54·4
55·5
55·6
56·1
56·4
56·6
56·2
56·1
54·8
54·4
53·8
53·3
54·1
53·0
53·0
52·8 1·7
2·0
1·5
1·9
1·6
2·0
1·8
1·6
1·1
1·7
1·8
1·8
1·5
1·6
0·4
1·0
1·6
1·5
1·3 ·409
·403
·423
·434
·450
·451
·459
·463
·466
·460
·458
·439
·433
·424
·417
·429
·413
·413
·411 4·65
4·58
4·78
4·90
5·07
5·08
5·15
5·17
5·25
5·16
5·15
4·98
4·90
4·80
4·75
4·83
4·82
4·82
4·65 ·943
·025
·950
·935
·942
·935
·940
·950
·962
·940
·940
·948
·950
·950
·990
·965
·949
·950
·962 22·657
+·669
·663
·665
·650
·728
·613
·592
·567
·567
·–·566
·583
·600
·621
·621
·632
·659
·654
·657
G.
ON THE RELATIVE HUMIDITY, AND ABSOLUTE AMOUNT OF VAPOUR CONTAINED IN
THE ATMOSPHERE AT DIFFERENT ELEVATIONS IN THE SIKKIM HIMALAYA.