elevation equal to that of the summit of Mont Blanc in the Alps, and
descends, according to recent measurements, about 1023 feet lower toward the
northern tropic in the elevated plateaux of Mexico (in 19 degrees north
latitude), rises, according to Pentland, in the southern tropical zone (14
degrees 30' to 18 degrees south latitude), being more than 2665 feet higher
in the maritime and western branch of the Cordilleras of Chili than under
the equator near Quito on Chimborazo, Cotopaxi, and Antisana. Dr. Gilles
even asserts that much further to the south, on the declivity of the volcano
of Peuquenes (latitude 33 degrees), he found the snow-line at an elevation
of between 14,520 and 15,030 feet. The evaporation of the snow in the
extremely dry air of the summer, and under a cloudless sky, is so powerful,
that the volcano of Aconcagua, northeast of Valparaiso (latitude 32 degrees
30'), which was found in the expedition of the Beagle to be more than 1400
feet higher than Chimborazo, was on one occasion seen free from snow.•
[footnote] *Darwin, 'Journal of the Voyages of the Adventure and Beagle',
p. 297. As the volcano of Aconcagua was not at that time in a state of
eruption, we must not ascribe the remarkable phenomenon of this absence of
snow to the internal heat of the mountain (to the escape of heated air
through fissures), as is sometimes the case with Cotopaxi. Gilles, in the
'Journal of Natural Science', 1830, p. 316.
In
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an almost equal northern latitude (from 30 degrees 45' to 31 degrees), the
snow'line on the southern declivity of the Himalaya lies at an elevation of
12,982 feet, which is about the same as the height which we might have
assigned to it from a comparison with other mountain chains; on the northern
declivity, however, under the influence of the high lands of Thibet (whose
mean elevation appears to be about 11,510 feet), the snow-line is situated
at a height of 16,630 feet. This phenomenon, which has long been contested
both in Europe and in India, and whose causes I have attempted to develop in
various works, published since 1820,* possesses other grounds of interest
than
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those of a purely physical nature, since it exercises no inconsiderable
degree of influence on the mode of life of numerous tribes -- the
meteorological processes of the atmosphere being the controlling causes on
which depend the agricultural or pastoral pursuits of the inhabitants of
extensive tracts of continents.
[footnote] *See my 'Second Memoire sur les Montagnes de Inde', in the
'Annales de Chemie et de Physique', t. xiv., p. 5-55; and 'Asie Centrale',
t. iii., p. 281-327. While the most learned and experienced travelers in
India, Colebrooke, Webb, and Hodgson, Victor Jacquemont, Fobes Royle, Carl
von Hugel, and Vigne, who have all personally examined the Himalaya range,
are agreed, regarding the greater elevation of the snow-line on the
Thibeta=ian side, the accuracy of this statement is called in question by
John Gerard, by the geognoist MacClelland, the editor of the 'Calcutta
Journal', and by Captain Thomas Hutton, assistant surveyor of the Agra
Division. The appearance of my work on Central Asia gave rise to a
rediscussion of this question. A recent number (vol. iv., January, 1844) of
MacClelland and Griffith's 'Calcutta Journal of Natural History' contains,
however, a very remarkable and decisive notice of the determination of the
snow-line in the Himalaya. Mr. Batten, of the Bengal service, writes as
follows from Camp Semulka, on the Cosillah River, Kumaon: "In the July,
1843, No. 14 of your valuable Journal of Natural History, which I have only
lately had the opportunity of seeing, I read Captain Hutton's paper on the
snow of the Himalayas, and as I differed almost entirely from the
conclusions so confidently drawn by that gentleman, I thought it right, for
the interest of scientific truth, to prepare some kind of answer; as
however, on a more attentive perusal, I find that you yourself appear
implicitly to adopt Captain Hutton's views, and actually use these words,
'We have long been conscious of the error here so well ppointed out by
Captain Hutton, 'in common with every one who has visited the Himalayas,' I
feel more inclined to address you, in the first instance, and to ask whether
you will publish a short reply which I meditate; and whether your not to
Captain Hutton's paper was written after your own full and careful
examination of the subject, or merely on a general kind of acquiscence with
the fact and opinions of your able contributor, who is so well known and
esteemed as a collector of scientific data? Now I am one who have visited
the Himalaya on the western side; I have crossed the Borendo or Booria Pass
into the Buspa Valley, in Lower Kanawar, returning into the Rewaien
Mountains of Ghurwal by the Koopin Pass; I have visited the source of the
Jumna at Jumnootree; and, moving eastward, the sources of the Kalee or
Mundaknee branch of the Ganges at Kadarnath; of the Bishnoo Gunga, or
Aluknunda, at Buddrinath and Mana; of the Pindur at the foot of the Great
Peak Nundidavi; of the Dhoulee branch of the Ganges, beyond Neetee, crossing
and recrossing the pass of that name into Thibet; of the Goree or great
branch of the Sardah, or Kalee, near Oonta Dhoora, beyond Melum. I have
also, in my official capacity made the settlement of the Bhote Mehals of
this province. My residence of more than six years in the hills has thrown
me constantly in the way of European and native travelers, nor have I
neglected to acquire information from the recorded labors of others. Yet,
with all this experience, I am prepared to affirm that 'the perpetual
snow-line is at a higher elevation' on the northern slope of 'the Himalaya'
than on the southern slope.
"The facts mentioned by Captain Hutton appear to me only to refer to the
northern sides of all mountains in these regions, and not to affect, in any
way the reports of Captain Webb and others, on which Humboldt formed his
theory. Indeed how can any facts of one observer in one place falsify the
facts of another observer in another place? I willingly allow that the
north side of a hill retains the snow longer and deeper than the south side,
and this observation applies equally to heights in Bhote; but Humboldt's
theory is on the question of the perpetual snow-line, and Captain Hutton's
reference to Simla and Mussooree, and other mountain sites, are out of place
in this question, or else he fights against a shadow, or an objectioon of
his own creation. In no part of his paper does he quote accurately the
dictum which he wishes to oppose."
If the mean altitude of the thibetian highlands be 11,510 feet, they admit
of comparison with the lovely and fruitful plateau of Caxamarca in Peru.
But at this estimate they would still be 1300 feet lower than the plateau of
Bolivia at the Lake of Titicaca, and the causeway of the town of Potosi.
Ladak, as appears from Vigne's measurement, by determining the
boiling-point, is 9994 feet high. This is probably also the altitude of
H'Lassa (Yul-sung), a monastic city, which Chinese writers describe as the
'realm of pleasure', and which is surrounded by vineyards. Must not these
lie in deep valleys?
As the quantity of moisture in the atmosphere increases with the
temperature, this element, which is so important for the whole organic
creation, must vary with the hours of the day, the seasons of the year, and
the differences in latitude and elevation. Our knowledge of the hygrometric
relations of the Earth's surface has been very materially augmented of late
years by the general application of August's psychrometer, framed in
accordance with the views of Dalton and Daniell, for determining the
relative quantity of vapor, or the
p 333
condition of moisture of the atmosphere, by means of the difference of the
'dew point' and of the temperature of the air. Temperature, atmospheric
pressure, and the direction of the wind, are all intimately connected with
the vivifying action of atmospheric moisture. This influence is not,
however, so much a consequence of the quantity of moisture held in solution
in different zones, as of the nature and frequency of the precipitation
which moistens the ground, whether in the form of dew, mist, rain, or snow.
According to the exposition made by Dove of the law of rotation, and to the
general views of this distinguished physicist,* it would appear that, in our
northern zone, "the elastic force of the vapor is greatest with a southwest,
and least with a northeast wind. On the western side of the windrose this
elasticity diminishes, while it increases on the eastern side; on the former
side, for instance, the cold, dense, and dry current of air repels the
warmer, lighter current containing an abundance of aqueous vapor, while on
the eastern side it is the former current which is repulsed by the latter.
[footnote] *See Dove, 'Meteorologische Vergleichung von Nordamerika und
Europa', in Schumacher's 'Jahrbuch fur' 1841, s. 311; and his
'Meteorologische Untersuchungen', s. 140.
The agreeable and fresh verdure which is observed in many trees in districts
within the tropics, where, for five or seven months of the yeqar, not a
cloud is seen on the vault of heaven, and where no perceptible dew or rain
falls, proves that the leaves are capable of extyracting water from the
atmosphere by a peculiar vital process of their own, which perhaps is not
alone that of producing cold by radiation. The absence of rain in the arid
plains of Cumana, Coro, and Ceara in North Brazil, forms a striking contrast
to the quanitity of rain which falls in some tropical regions, as, for
instance, in the Havana, where it would appear, from the average of six
years' observation by Ramong de la Sagra, the mean annual quantity of rain
is 109 inches, equal to four or five times that which falls at Paris or at
Geneva.*
[footnote] *The mean annual quantity of rain that fell in Paris between
1805 and 1822 was found by Arago to be 20 inches; in London, between 1812
and 1827, it was determined by Howard at 25 inches; while at Geneva the mean
of thirty-two years' observation was 30.5 inches. In Hindostan, near the
coast, the quantity of rain is from 115 to 128 inches; and in the island of
Cuba, fully 142 inches fell in the year 1821. With regard to the
distribution of the quantity of rain in Central Europe, at different periods
of the year, see the admirable researches of Gasparin, Schuow, and Bravais,
in the 'Bibliotheque Universelle', t. xxxvviii., p. 54 and 264; 'Tableau du
Climat de l'Italie', p. 76; and Martins's notes to his excellent French
translation of Kämtz's 'Vorlesungen uber Meteorologie', p. 142.
On the declivity of the Cordilleras,
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the quantity of rain, as well as the temperature, diminishes with the
increase in the elevation.*
[footnote] *According to Boussingault ('Economie Rurale', t. ii., p. 693),
the mean quantity of rain that fell at Marmato (latitude 5 degrees 27',
altitude 4675 feet, and mean temperature 69 degrees) in the years 1833 and
1834 was 64 inches, while at Santa Fe de Bogota (latitude 4 degrees 36',
altitude 8685 feet, and mean temperature 58 degrees) it only amounted to 39
1/2 inches.
My South American fellow-traveler, Caldas, found that, at Santa Fe de
Bogota, at an elevation of almost 8700 feet, it did not exceed 37 inches,
being consequently little more than on some parts of the western shore of
Europe. Boussingault occasionally observed at Quito that Saussure's
hygrometer receded to 26 degrees with a temperature of from 53.6 degrees to
55.4 degrees. Gay-Lussac saw the same hygrometer standing at 25.3 degrees
in his great aerostatic ascent in a stratum of air 7034 feet high, and with
a temperature of 39.2 degrees. The greatest dryness that has yet been
observed on the surface of the globe in the low lands is probably that which
Gustav Rose, Ehrenberg, and myself found in Northern Asia, between the
valleys of the Irtisch and the Oby. In the Steppe of Platowskaja, after
southwest winds had blown for a long time from the interior of the
Continent, with a temperature of 74.7 degrees, we found the dew point at 24
degrees. The air contained only 16/100ths of aqueous vapor.*
[footnote] *For the particulars of this observation, see my 'Asie
Centrale', t. iii., p. 85-89 and 467; and regarding the amount of vapor in
the atmosphere in the lowlands of tropical South America, consult my 'Relat.
Hist.', t. i., p. 242-248; t. ii., p. 45, 164.
The accurate observers Kämtz, Bravais, and Martins have raised doubts
during the last few years regarding the greater dryness of the mountain air,
which appeared to be proved by the hygrometric measurements made by Saussure
and myself in the higher regions of the Alps and the Cordilleras. The
strata of air at Zurich and on the Faulhorn, which can not be considered as
an elevated mountain when compared with non-European elevations, furnished
the data employed in the comparisons made by these observers.*
[footnote] *Kämtz, 'Vorlesungen uber Meteorologie', s. 117.
In the tropical region of the Paramos (near the region where snow begins to
fall, at an elevation of between 12,000 and 14,000 feet), some species of
large flowering myrtle-leaved alpine shrubs are almost constantly bathed in
moisture; but this fqact does not actually prove the existence of any great
and absolute quantity of aqueous vapor at such an elevation, merely affording
p 335
an evidence of the frequency of aqueous precipitation, in like manner as do
the frequent mists with which the lovely plateau of Bogota is covered.
Mists arise and disappear several times in the course of an hour in such
elevations as these, and with a calm state of the atmosphere. These rapid
alternations characterize the Paramos and the elevated plains of the chain
of the Andes.
'The electricity of the atmosphere', whether considered in the lower or in
the upper strata of the clouds, in its silent problematical diurnal course,
or in the explosion of the lightning and thunder of the tempest, appears to
stand in a manifold relation to all phenomena of the distribution of heat,
of the pressure of the atmosphere and its disturbances, of hydrometeoric
exhibitions, and probably, also, of the magnetism of the external crust of
the earth. It exercises a powerful influence on the whole animal and
vegetable world; not merely by meteorological processes, as precipitations
of aqueous vapor, and of the acids and ammoniacal compounds to which it
gives rise, but also directly as an electric force acting on the nerves, and
promoting the circulation of the organic juices. This is not a place in
which to renew the discussion that has been started regarding the actual
source of atmospheric eletricity when the sky is clear, a phenomenon that
has alternately been ascribed to the evaporation of impure fluids
impregnated with earths and salts,* to the growth of plants,** or to some
other chemical decompositions on the surface of the earth, to the unequal
distribution of heat in the strata of the air,*** and, finally, according to
Peltier's intelligent researches,**** to the agency of a constant charge of
negative electricity in the terrestrial globe.
[footnote] *Regarding the conditions of electricity from evaporation at
high temperatures, see Peltier, in the 'Annales de Chimie', t. lxxv., p. 330.
[footnote] **Pouillet, in the 'Annales de Chimie', t. xxxv., p. 405.
[footnote] ***De la Rive, in his admirable 'Essai Historique sur
l'Electricite', p. 140.
[footnote] ****Peltier, in the 'Comptes Rendus de l'Acad. des Sciences', t.
xii., p. 307; Becquerel, 'Traite de l'Electricite et du Magnetisme', t. iv.,
p. 107.
Limiting itself to results yielded by electrometric observations, such, for
instance, as are furnished by the ingenious electro-magnetic apparatus first
proposed by Colladon, the physical description of the universe should merely
notice the incontestable increase of intensity in the general positive
electricity of the atmosphere,* accompanying an increase of altitude and and
the absence of trees, its daily variations (which, according to Clark's
experiments at Dublin,
p 336
take place at more complicated periods than those found by Saussure and
myself), and its variations in the different seasons of the year, at
different distances from the equator, and in the different relations of
continental or oceanic surface.
[footnote] *Duprez, 'Sur l'Electricite de l'Air' (Bruxelles, 1844), p.
56-61.
The electric equilibrium is less frequently disturbed where the aerial ocean
rests on a liquid base than where it impends over the land; and it is very
striking to observe how, in extensive seas, small insular groups affect the
condition of the atmosphere, and occasion the formation of storms. In fogs,
and in the commencement of falls of snow, I have seen, in a long series of
observations, the previously permanent positive electricity rapidly pass
into the negative condition, both on the plains of the colder zones, and in
the Paramos of the Cordilleras, at elevations varying from 11,000 to 15,000
feet. The alternate transition was precisly similar to that indicated by
the electrometer shortly before and during a storm.*
[footnote] *Humboldt, 'Relation Historique', t. iii., p. 318. I here only
refer to those of my experiiments in which the three-foot metallic conductor
of Saussure's electrometer was neither moved upward nor downward, nor,
according to Volta's proposal, armed with burning sponge. Those of my
readers who are well acquainted with the 'quaestiones vexatae' of
atmospheric electricity will understand the grounds for this limitation.
Respecting the formation of storms in the tropics, see my 'Rel. Hist.', t.
ii., p. 45 and 202-209.
When the vesicles of vapor have become condensed into clouds, having
definite outlines, the electric tension of the external surface will be
increased in proportion to the amount of electricity which passes over to it
from the separate vesicles of vapor.*
[footnote] *Gay-Lussac, in the 'Annales de Chimie et de Physique', t.
viii., p. 167. In consequence of the discordant views of Lame, Becquerel,
and Peltier, it is difficult to come to a conclusion regarding the cause of
the specific distribution of electricity in clouds, some of which have a
positive, and others a negative tension. The negative electricity of the
air, which near high water-falls is caused by a disintegration of the drops
of water -- a fact originally noticed by Tralles, and confirmed by myself in
various latitudes -- is very remarkable, and is sufficiently intense to
produce an appreciable effect on a delicate electrometer at a distance of
300 or 400 feet.
Slate-gray clouds are charged, according to Peltier's experiments at Paris,
with negative, and white, red, and orange-colored clouds with positive
electricity. Thunder clouds not only envelop the highest summits of the
chain of the Andes (I have myself seen the electric effect of lightning on
one of the rocky pinnacles which project upward of 15,000 feet above the
crater of the volcano of Toluca), but they have also been observed at a
vertical height of 26,650 feet over the low
p 337
lands in the temperate zone.*
[footnote] *Arago, in the 'Annuaire du Bureau des Longitudes pour' 1838, p.
246.
Sometimes, however, the stratum of cloud from which the thunder proceeds
sinks to a distance of 5000, or, indeed, only 3000 feet above the plain.
According to Arago's investigations -- the most comprehensive that we
possess on this difficult branch of meteorology -- the evolution of light
(lightning) is of three kinds -- zigzag, and sharply defined at the edges;
in sheets of light, illuminating a whole cloud, which seems to open and
refeal the light within it; and in the form of fire-balls.*
[footnote] *Arago, op. cit., p. 249-266. (See also, p. 268-279.)
The duration of the two first kinds scarcely continues the thousandth part
of a second; but the globular lightning moves much more slowly remaining
visible for several seconds. Occasionally (as is proved by the recent
observations, which have confirmed the description given by Nicholson and
Beccaria of this phenomenon), isolated clouds, standing high above the
horizon, continue uninterruptedly for some time to emit a luminous radiance
from their interior and from their margins, although there is no thunder to
be heard, and no indication of a storm; in some cases even hail-stones,
drops of rain, and flakes of snow have been seen to fall in a luminous
condition, when the phenomenon was not preceded by thunder. In the
geographical distribution of storms, the Peruvian coast, which is not
visited by thunder or lightning, presents the most striking contrast to the
rest of the tropical zone, in which, at certain seasons of the year,
thunder-storms occur almost daily, about four or five hours after the sun
has reached the meridian. According to the abundant evidence collected by
Arago* from the testiimony of navigators (Scoresby, Parry, Ross, and
Franklin), there can be no doubt that, in general, electric explosions are
extremely rare in high northern regions (between 70 degrees and 75 degrees
latitude).
[footnote] *Arago, op. cit., p. 388-391. The learned academician Von Baer,
who has done so much for the meteorology of Northern Asia, has not taken
into consideration the extreme rarity of storms in Iceland and Greenland; he
has only remarked ('Bulletin de l'Academie de St. Petersbourg', 1839, Mai)
that in Nova Zembla and Spitzbergen it is sometimes heard to thunder.
'The meteorological portion' of the descriptive history of nature which we
are now concluding shows that the processes of the absorption of light, the
liberation of heat, and the variations in the elastic and electric tension,
and in the hygrometric condition of the vast aerial ocean, are all so
intimately connected together, that each individual meteorological process
is modified by the action of all the others. The complicated
p 338
nature of these disturbing causes (which involuntarily remind us of those
which the near and especially the smallest cosmical bodies, the satellites,
comets, and shooting stars, are subjected to in their course) increases the
difficulty of giving a full explanation of these involved meteorological
phenomena, and likewise limits, or wholly precludes, the possibility of that
predetermination of atmospheric changes which would be so important for
horticulture, agriculture, and navigation, no less than for the comfort and
enjoyment of life. Those who place the value of meteorology in this
problematic species of prediction rather than in the knowledge of the
phenomena themselves, are firmly convinced that this branch of science, on
account of which so many expeditions to distant mountainous regions have
been undertaken, has not made any very considerable progress for centuries
past. The confidence which they refuse to the physicist they yield to
changes of the moon, and to certain days marked in the calendar by the
superstition of a by-gone age.
"Great local deviations from the distribution of the mean temperature are of
rare occurrence, the variations being in general uniformly distributed over
extensive tracts of land. the deviation, after attaining its maximum at a
certain point, gradually decreases to its limits; when these are passed,
however, decided deviations are observed in the 'opposite direction'.
Similar relations of weather extend more frequently from south to north than
from west to east. At the close of the year 1829 (when I had just completed
my Siberian journey), the maximum of cold was at Berlin, while North America
enjoyed an unusually high temperature. It is an entirely arbitrary
assumption to believe that a hot summer succeeds a severe winter, and that a
cool summer is preceded by a mild winter." Opposite relations of weather in
contiguous countries, or in two corn-growing continents, give rise to a
beneficient equalization in the prices of the products of the vine, and of
agricultural and horticultural cultivation. It has been justy remarked,
that it is the barometer alone which indicates to us the changes that occur
in the pressure of the air throughout all the aerial strata from the place
of observation to the extremest confines of the atmosphere, while* the
thermometer and psychrometer only acquaint us with all the variations
occurring in the local heat and moisture of the lower strata of
p 339
air in contact with the ground.