liable to eddies than water, and that these eddies must extend into
cylinders or vortexes of greater diameter, and that if a vertical eddy
of north-east air be of small diameter or has passed but a little way to
the south of us before its return, it will not have gained the velocity
of the earth's surface to the south of us, and will in consequence
become a south-east wind.--But if the vertical eddy be of large
diameter, or has passed much to the south of us, it will have acquired
velocity from its friction with the earth's surface to the south of us,
and will in consequence on its return become a south-west wind,
producing great cold.
NORTH-WEST WINDS.
There seem to be three sources of the north-west winds of this
hemisphere of the earth. 1. When a portion of southern air, which was
passing over us, is driven back by accumulation of new air in the polar
regions. In this case I suppose they are generally moist or rainy winds,
with the barometer under 30, and if the wind had previously been in the
south-west, it would seem to prognosticate a change to the north-east.
2. If a current of north wind is passing over us but a few miles high,
without any easterly direction; and is bent down upon us, it must
immediately possess a westerly direction, because it will now move
faster than the surface of the earth where it arrives; and thus becomes
changed from a north-east to a north-west wind. This descent of a north-
east current of air producing a north-west wind may continue some days
with clear or freezing weather, as it may be simply owing to a vertical
eddy of north-east air, as will be spoken of below. It may otherwise be
forced down by a current of south-west wind passing over it, and in this
case it will be attended with rain for a few days by the mixture of the
two airs of different degrees of heat; and will prognosticate a change
of wind from north-east to south-west if the wind was previously in the
north-east quarter.
3. On the eastern coast of North America the north-west winds bring
frost, as the north-east winds do in this country, as appears from
variety of testimony. This seems to happen from a vertical spiral eddy
made in the atmosphere between the shore and the ridge of mountains
which form the spine or back-bone of that continent. If a current of
water runs along the hypothenuse of a triangle an eddy will be made in
the included angle, which will turn round like a water-wheel as the
stream passes in contact with one edge of it. The same must happen when
a sheet of air flowing along from the north-east rises from the shore in
a straight line to the summit of the Apalachian mountains, a part of the
stream of north-east air will flow over the mountains, another part will
revert and circulate spirally between the summit of the country and the
eastern shore, continuing to move toward the south; and thus be changed
from a north-east to a north-west wind.
This vertical spiral eddy having been in contact with the cold summits
of these mountains, and descending from higher parts of the atmosphere
will lose part of its heat, and thus constitute one cause of the greater
coldness of the eastern sides of North America than of the European
shores opposite to them, which is said to be equal to twelve degrees of
north latitude, which is a wonderful fact, not otherwise easy to be
explained, since the heat of the springs at Philadelphia is said to be
50, which is greater than the medium heat of the earth in this country.
The existence of vertical eddies, or great cylinders of air rolling on
the surface of the earth, is agreeable to the observations of the
constructors of windmills; who on this idea place the area of the sails
leaning backwards, inclined to the horizon; and believe that then they
have greater power than when they are placed quite perpendicularly. The
same kind of rolling cylinders of water obtain in rivers owing to the
friction of the water against the earth at their bottoms; as is known by
bodies having been observed to float upon their surfaces quicker than
when immersed to a certain depth. These vertical eddies of air probably
exist all over the earth's surface, but particularly at the bottom or
sides of mountains; and more so probably in the course of the south-west
than of the north-east winds; because the former fall from an eminence,
as it were, on a part of the earth where there is a deficiency of the
quantity of air; as is shewn by the sinking of the barometer: whereas
the latter are pushed or squeezed forward by an addition to the
atmosphere behind them, as appears by the rising of the barometer.
TRADE-WINDS.
A column of heated air becomes lighter than before, and will therefore
ascend, by the pressure of the cold air which surrounds it, like a cork
in water, or like heated smoke in a chimney.
Now as the sun passes twice over the equator for once over either
tropic, the equator has not time to become cool; and on this account it
is in general hotter at the line than at the tropics; and therefore the
air over the line, except in some few instances hereafter to be
mentioned, continues to ascend at all seasons of the year, pressed
upwards by regions of air brought from the tropics.
This air thus brought from the tropics to the equator, would constitute
a north wind on one side of the equator, and a south wind on the other;
but as the surface of the earth at the equator moves quicker than the
surface of the earth at the tropics, it is evident that a region of air
brought from either tropic to the equator, and which had previously only
acquired the velocity of the earth's surface at the tropics, will now
move too slow for the earth's surface at the equator, and will thence
appear to move in a direction contrary to the motion of the earth. Hence
the trade-winds, though they consist of regions of air brought from the
north on one side of the line, and from the south on the other, will
appear to have the diagonal direction of north-east and south-west
winds.
Now it is commonly believed that there are superior currents of air
passing over these north-east and south-west currents in a contrary
direction, and which descending near the tropics produce vertical
whirlpools of air. An important question here again presents itself,
_What becomes of the moisture which this heated air ought to deposit, as
it cools in the upper regions of the atmosphere in its journey to the
tropics?_ It has been shewn by Dr. Priestley and Mr. Ingenhouz that the
green matter at the bottom of cisterns, and the fresh leaves of plants
immersed in water, give out considerable quantities of vital air in the
sun-shine; that is, the perspirable matter of plants (which is water
much divided in its egress from their minute pores) becomes decomposed
by the sun's light, and converted into two kinds of air, the vital and
inflammable airs. The moisture contained or dissolved in the ascending
heated air at the line must exist in great tenuity; and by being exposed
to the great light of the sun in that climate, the water may be
decomposed, and the new airs spread on the atmosphere from the line to
the poles.
1. From there being no constant deposition of rains in the usual course
of the trade-winds, it would appear that the water rising at the line is
decomposed in its ascent.
2. From the observations of M. Bougner on the mountain Pinchinca, one of
the Cordelieres immediately under the line, there appears to be no
condensible vapour above three or four miles high. Now though the
atmosphere at that height may be cold to a very considerable degree; yet
its total deprivation of condensible vapour would seem to shew, that its
water was decomposed; as there are no experiments to evince that any
degree of cold hitherto known has been able to deprive air of its
moisture; and great abundance of snow is deposited from the air that
flows to the polar regions, though it is exposed to no greater degrees
of cold in its journey thither than probably exists at four miles height
in the atmosphere at the line.
3. The hygrometer of Mr. Sauffure also pointed to dryness as he ascended
into rarer air; the single hair of which it was constructed, contracting
from deficiency of moisture. Essais sur l'Hygromet. p. 143.
From these observations it appears either that rare and cold air
requires more moisture to saturate it than dense air; or that the
moisture becomes decomposed and converted into air, as it ascends into
these cold and rare regions of the atmosphere.
4. There seems some analogy between the circumstance of air being
produced or generated in the cold parts of the atmosphere both at the
line and at the poles.
MONSOONS AND TORNADOES.
1. In the Arabian and Indian seas are winds, which blow six months one
way, and six months the other, and are called Monsoons; by the
accidental dispositions of land and sea it happens, that in some places
the air near the tropic is supposed to become warmer when the sun is
vertical over it, than at the line. The air in these places
consequently ascends pressed upon one side by the north-east regions of
air, and on the other side by the south-west regions of air. For as the
air brought from the south has previously obtained the velocity of the
earth's surface at the line, it moves faster than the earth's surface
near the tropic where it now arrives, and becomes a south-west wind,
while the air from the north becomes a north-east wind as before
explained. These two winds do not so quietly join and ascend as the
north-east and south-east winds, which meet at the line with equal
warmth and velocity and form the trade-winds; but as they meet in
contrary directions before they ascend, and cannot be supposed
accurately to balance each other, a rotatory motion will be produced as
they ascend like water falling through a hole, and an horizontal or
spiral eddy is the consequence; these eddies are more or less rapid, and
are called Tornadoes in their most violent state, raising water from the
ocean in the west or sand from the deserts of the east, in less violent
degrees they only mix together the two currents of north-east and south-
west air, and produce by this means incessant rains, as the air of the
north-east acquires some of the heat from the south-west wind, as
explained in Note XXV. This circumstance of the eddies produced by the
monsoon-winds was seen by Mr. Bruce in Abyssinia; he relates that for
many successive mornings at the commencement of the rainy monsoon, he
observed a cloud of apparently small dimensions whirling round with
great rapidity, and in few minutes the heavens became covered with dark
clouds with consequent great rains. See Note on Canto III. l. 129.
2. But it is not only at the place where the air ascends at the northern
extremity of the rainy monsoon, and where it forms tornadoes, as
observed above by Mr. Bruce, but over a great tract of country several
degrees in length in certain parts as in the Arabian sea, a perpetual
rain for several months descends, similar to what happens for weeks
together in our own climate in a less degree during the south-west
winds. Another important question presents itself here, _if the climate
to which this south-west wind arrives, it not colder than that it comes
from, why should it deposit its moisture during its whole journey? if it
be a colder climate, why does it come thither?_ The tornadoes of air
above described can extend but a little way, and it is not easy to
conceive that a superior cold current of air can mix with an inferior
one, and thus produce showers over ten degrees of country, since at
about three miles high there is perpetual frost; and what can induce
these narrow and shallow currents to flow over each other so many
hundred miles?
Though the earth at the northren extremity of this monsoon may be more
heated by certain circumstances of situation than at the line, yet it
seems probable that the intermediate country between that and the line,
may continue colder than the line (as in other parts of the earth) and
hence that the air coming from the line to supply this ascent or
destruction of air at the northern extremity of the monsoon will be
cooled all the way in its approach, and in consequence deposit its
water. It seems probable that at the northern extremity of this monsoon,
where the tornadoes or hurricanes exist, that the air not only ascends
but is in part converted into water, or otherwise diminished in
quantity, as no account is given of the existence of any superior
currents of it.
As the south-west winds are always attended with a light atmosphere, an
incipient vacancy, or a great diminution of air must have taken place to
the northward of them in all parts of the earth wherever they exist, and
a deposition of their moisture succeeds their being cooled by the
climate they arrive at, and not by a contrary current of cold air over
them, since in that case the barometer would not sink. They may thus in
our own country be termed monsoons without very regular periods.
3. Another cause of TORNADOES independent of the monsoons is ingeniously
explained by Dr. Franklin, when in the tropical countries a stratum of
inferior air becomes so heated by its contact with the warm earth, that
its expansion is increased more than is equivalent to the pressure of
the stratum of air over it; or when the superior stratum becomes more
condensed by cold than the inferior one by pressure, the upper region
will descend and the lower one ascend. In this situation if one part of
the atmosphere be hotter from some fortuitous circumstances, or, has
less pressure over it, the lower stratum will begin to ascend at this
part, and resemble water falling through a hole as mentioned above. If
the lower region of air was going forwards with considerable velocity,
it will gain an eddy by riling up this hole in the incumbent heavy air,
so that the whirlpool or tornado has not only its progressive velocity,
but its circular one also, which thus lifts up or overturns every thing
within its spiral whirl. By the weaker whirlwinds in this country the
trees are sometimes thrown down in a line of only twenty or forty yards
in breadth, making a kind of avenue through a country. In the West
Indies the sea rises like a cone in the whirl, and is met by black
clouds produced by the cold upper air and the warm lower air being
rapidly mixed; whence are produced the great and sudden rains called
water-spouts; while the upper and lower airs exchange their plus or
minus electricity in perpetual lightenings.
LAND AND SEA-BREEZES.
The sea being a transparent mass is less heated at its surface by the
sun's rays than the land, and its continual change of surface
contributes to preserve a greater uniformity in the heat of the air
which hangs over it. Hence the surface of the tropical islands is more
heated during the day than the sea that surrounds them, and cools more
in the night by its greater elevation: whence in the afternoon when the
lands of the tropical islands have been much heated by the sun, the air
over them ascends pressed upwards by the cooler air of the incircling
ocean, in the morning again the land becoming cooled more than the sea,
the air over it descends by its increased gravity, and blows over the
ocean near its shores.
CONCLUSION.
1. There are various irregular winds besides those above described,
which consist of horizontal or vertical eddies of air owing to the
inequality of the earth's surface, or the juxtaposition of the sea.
Other irregular winds have their origin from increased evaporation of
water, or its sudden devaporation and descent in showers; others from
the partial expansion and condensation of air by heat and cold; by the
accumulation or defect of electric fluid, or to the air's new production
or absorption occasioned by local causes not yet discovered. See Notes
VII. and XXV.
2. There seem to exist only two original winds: one consisting of air
brought from the north, and the other of air brought from the south. The
former of these winds has also generally an apparent direction from the
east, and the latter from the west, arising from the different
velocities of the earth's surface. All the other winds above described
are deflections or retrogressions of some parts of these currents of air
from the north or south.
3. One fifteenth part of the atmosphere is occasionally destroyed, and
occasionally reproduced by unknown causes. These causes are brought into
immediate activity over a great part of the surface of the earth at
nearly the same time, but always act more powerful to the northward than
to the southward of any given place; and would hence seem to have their
principal effect in the polar circles, existing nevertheless though with
less power toward the tropics or at the line.
For when the north-east wind blows the barometer rises, sometimes from
281/2 inches to 301/2, which shews a great new generation of air in the
north; and when the south-west wind blows the barometer sinks as much,
which shews a great destruction of air in the north. But as the north-
east winds sometimes continue for five or six weeks, the newly-generated
air must be destroyed at those times in the warmer climates to the south
of us, or circulate in superior currents, which has been shewn to be
improbable from its not depositing its water. And as the south-west
winds sometimes continue for some weeks, there must be a generation of
air to the south at those times, or superior currents, which last has
been shewn to be improbable.
4. The north-east winds being generated about the poles are pushed
forwards towards the tropics or line, by the pressure from behind, and
hence they become warmer, as explained in Note VII. as well as by their
coming into contact with a warmer part of the earth which contributes to
make these winds greedily absorb moisture in their passage. On the
contrary, the south-west winds, as the atmosphere is suddenly diminished
in the polar regions, are drawn as it were into an incipient vacancy,
and become therefore expanded in their passage, and thus generate cold,
as explained in Note VII. and are thus induced to part with their
moisture, as well as by their contact with a colder part of the earth's
surface. Add to this, that the difference in the sound of the north-east
and south-west winds may depend on the former being pushed forwards by a
pressure behind, and the latter falling as it were into a partial or
incipient vacancy before; whence the former becomes more condensed, and
the latter more rarefied as it passes. There is a whistle, termed a
lark-call, which consists of a hollow cylinder of tin-plate, closed at
each end, about half an inch in diameter and a quarter of an inch high,
with opposite holes about the size of a goose-quill through the centre
of each end; if this lark-whistle be held between the lips the sound of
it is manifestly different when the breath is forceably blown through it
from within outwards, and when it is sucked from without inwards.
Perhaps this might be worthy the attention of organ-builders.
5. A stop is put to this new generation of air, when about a fifteenth
of the whole is produced, by its increasing pressure; and a similar
boundary is fixed to its absorption or destruction by the decrease of
atmospheric pressure. As water requires more heat to convert it into
vapour under a heavy atmosphere than under a light one, so in letting
off the water from muddy fish-ponds great quantities of air-bubbles are
seen to ascend from the bottom, which were previously confined there by
the pressure of the water. Similar bubbles of inflammable air are seen
to arise from lakes in many seasons of the year, when the atmosphere
suddenly becomes light.
6. The increased absorptions and evolutions of air must, like its simple
expansions, depend much on the presence or absence of heat and light,
and will hence, in respect to the times and places of its production and
destruction, be governed by the approach or retrocession of the sun, and
on the temperature, in regard to heat, of various latitudes, and parts
of the same latitude, so well explained by Mr. Kirwan.
7. Though the immediate cause of the destruction or reproduction of
great masses of air at certain times, when the wind changes from north
to south, or from south to north can not yet be ascertained; yet as
there appears greater difficulty in accounting for this change of wind
for any other known causes, we may still suspect that there exists in
the arctic and antarctic circles a BEAR or DRAGON yet unknown to
philosophers, which at times suddenly drinks up, and as suddenly at
other times vomits out one-fifteenth part of the atmosphere: and hope
that this or some future age will learn how to govern and domesticate a
monster which might be rendered of such important service to mankind.
INSTRUMENTS.
If along with the usual registers of the weather observations were made
on the winds in many parts of the earth with the three following
instruments, which might be constructed at no great expence, some useful
information might be acquired.
1. To mark the hour when the wind changes from north-east to south-west,
and the contrary. This might be managed by making a communication from
the vane of a weathercock to a clock; in such a manner, that if the vane
mould revolve quite round, a tooth on its revolving axis should stop the
clock, or put back a small bolt on the edge of a wheel revolving once in
twenty-four hours.
2. To discover whether in a year more air passed from north to south, or
the contrary. This might be effected by placing a windmill-sail of
copper about nine inches diameter in a hollow cylinder about six inches
long, open at both ends, and fixed on an eminent situation exactly north
and south. Thence only a part of the north-east and south-west currents
would affect the sail so as to turn it; and if its revolutions were
counted by an adapted machinery, as the sail would turn one way with the
north currents of air, and the contrary one with the south currents, the
advance of the counting finger either way would shew which wind had
prevailed most at the end of the year.
3. To discover the rolling cylinders of air, the vane of a weathercock
might be so suspended as to dip or rise vertically, as well as to have
its horizontal rotation.
RECAPITULATION.
NORTH-EAST WINDS consist of air flowing from the north, where it seems
to be occasionally produced; has an apparent direction from the east
owing to its not having acquired in its journey the increasing velocity
of the earth's surface; these winds are analogous to the trade-winds
between the tropics, and frequently continue in the vernal months for
four and six weeks together, with a high barometer, and fair or frosty
weather. 2. They sometimes consist of south-west air, which had passed
by us or over us, driven back by a new accumulation of air in the north,
These continue but a day or two, and are attended with rain. See Note
XXV.
SOUTH-WEST WIND consists of air flowing from the south, and seems
occasionally absorbed at its arrival to the more northern latitudes. It
has a real direction from the west owing to its not having lost in its
journey the greater velocity it had acquired from the earth's surface
from whence it came. These winds are analogous to the monsoons between
the tropics, and frequently continue for four or six weeks together,
with a low barometer and rainy weather. 2. They sometimes consist of
north-east air, which had passed by us or over us, which becomes
retrograde by a commencing deficiency of air in the north. These winds
continue but a day or two, attended with severer frost with a sinking
barometer; their cold being increased by their expansion, as they
return, into an incipient vacancy.
NORTH-WEST WINDS consist, first, of south-west winds, which have passed
over us, bent down and driven back towards the south by newly generated
northern air. They continue but a day or two, and are attended with rain
or clouds. 2. They consist of north-east winds bent down from the higher
parts of the atmosphere, and having there acquired a greater velocity
than, the earth's surface; are frosty or fair. 3. They consist of north-
east winds formed into a vertical spiral eddy, as on the eastern coasts
of North America, and bring severe frost.
SOUTH-EAST WINDS consist, first, of north-east winds become retrograde,
continue for a day or two, frosty or fair, sinking barometer. 2. They
consist of north-east winds formed into a vertical eddy not a spiral
one, frost or fair.
NORTH WINDS consist, first, of air flowing slowly from the north, so
that they acquire the velocity of the earth's surface as they approach,
are fair or frosty, seldom occur. 2. They consist of retrograde south
winds; these continue but a day or two, are preceded by south-west
winds; and are generally succeeded by north-east winds, cloudy or rainy,
barometer rising.
SOUTH WINDS consist, first, of air flowing slowly from the south,
loosing their previous western velocity by the friction of the earth's
surface as they approach, moist, seldom occur, 2. They consist of
retrograde north winds; these continue but a day or two, are preceded by
north-east winds, and generally succeeded by south-west winds, colder,
barometer sinking.
EAST WINDS consist of air brought hastily from the north, and not
impelled farther southward, owing to a sudden beginning absorption of
air in the northern regions, very cold, barometer high, generally
succeeded by south-west wind.
WEST WINDS consist of air brought hastily from the south, and checked
from proceeding further to the north by a beginning production of air in
the northern regions, warm and moist, generally succeeded by north-east
wind. 2. They consist of air bent down from the higher regions of the
atmosphere, if this air be from the south, and brought hastily it
becomes a wind of great velocity, moving perhaps 60 miles an hour, is
warm and rainy; if it consists of northern air bent down it is of less
velocity and colder.
_Application of the preceding Theory to Some Extracts
from a Journal of the Weather._
_Dec. 1, 1790._ The barometer sunk suddenly, and the wind, which had
been some days north-east with frost, changed to south-east with an
incessant though moderate fall of snow. A part of the northern air,
which had passed by us I suppose, now became retrograde before it had
acquired the velocity of the earth's surface to the south of us, and
being attended by some of the southern air in its journey, the moisture
of the latter became condensed and frozen by its mixture mith the
former.
_Dec. 2, 3._ The wind changed to north-west and thawed the snow. A part
of the southern air, which had passed by us or over us, with the
retrograde northern air above described, was now in its turn driven
back, before it had lost the velocity of the surface of the earth to the
south of us, and consequently became a north-west wind; and not having
lost the warmth it brought from the south produced a thaw.
_Dec. 4, 5._ Wind changed to north-east with frost and a rising
barometer. The air from the north continuing to blow, after it had
driven back the southern air as above described, became a north-east
wind, having less velocity than the surface of the earth in this
climate, and produced frost from its coldness.
_Dec. 6, 7._ Wind now changed to the south-west with incessant rain and
a sinking barometer. From unknown causes I suppose the quantity of air
to be diminished in the polar regions, and the southern air cooled by
the earth's surface, which was previously frozen, deposits its moisture
for a day or two; afterwards the wind continued south-west without rain,
as the surface of the earth became warmer.
_March 18, 1785._ There has been a long frost; a few days ago the
barometer sunk to 291/2, and the frost became more severe. Because the air
being expanded by a part of the pressure being taken off became colder.
This day the mercury rose to 30, and the frost ceased, the wind
continuing as before between north and east. _March 19._ Mercury above
30, weather still milder, no frost, wind north-east. _March 20._ The
same, for the mercury rising shews that the air becomes more compressed
by the weight above, and in consequence gives out warmth.
_April 4, 5._ Frost, wind north-east, the wind changed in the middle of
the day to the north-west without rain, and has done so for three or
four days, becoming again north-east at night. For the sun now giving
greater degrees of heat, the air ascends as the sun passes the zenith,
and is supplied below by the air on the western side as well as on the
eastern side of the zenith during the hot part of the day; whence for a
few hours, on the approach of the hot part of the day, the air acquires
a westerly direction in this longitude. If the north-west wind had been
caused by a retrograde motion of some southern air, which had passed
over us, it would have been attended with rain or clouds.
_April 10._ It rained all day yesterday, the wind north-west, this
morning there was a sharp frost. The evaporation of the moisture, (which
fell yesterday) occasioned by the continuance of the wind, produced so
much cold as to freeze the dew.
_May 12._ Frequent showers with a current of colder wind preceding every
shower. The sinking of the rain or cloud pressed away the air from
beneath it in its descent, which having been for a time shaded from the
sun by the floating cloud, became cooled in some degree.
_June 20._ The barometer sunk, the wind became south-west, and the whole
heaven was instantly covered with clouds. A part of the incumbent
atmosphere having vanished, as appeared by the sinking of the barometer,
the remainder became expanded by its elasticity, and thence attracted
some of the matter of heat from the vapour intermixed with it, and thus
in a few minutes a total devaporation took place, as in exhausting the
receiver of an air-pump. See note XXV. At the place where the air is
destroyed, currents both from the north and south flow in to supply the
deficiency, (for it has been shewn that there are no other proper winds
but these two) and the mixture of these winds produces so sudden
condensation of the moisture, both by the coldness of the northern air
and the expansion of both of them, that lightning is given out, and an
incipient tornado takes place; whence thunder is said frequently to
approach against the wind.
_August 28, 1732._ Barometer was at 31, and _Dec. 30_, in the same year,
it was at 28 2-tenths. Medical Essays, Edinburgh, Vol. II. p. 7. It
appears from these journals that the mercury at Edinburgh varies
sometimes nearly three inches, or one tenth of the whole atmosphere.
From the journals kept by the Royal Society at London it appears seldom
to vary more than two inches, or one-fifteenth of the whole atmosphere.
The quantity of the variation is said still to decrease nearer the line,
and to increase in the more northern latitudes; which much confirms the
idea that there exists at certain times a great destruction or
production of air within the polar circle.
_July 2, 1732._ The westerly winds in the journal in the Medical Essays,
Vol. II. above referred to, are frequently marked with the number three
to shew their greater velocity, whereas the easterly winds seldom
approach to the number two. The greater velocity of the westerly winds
than the easterly ones is well known I believe in every climate of the
world; which may be thus explained from the theory above delivered. 1.
When the air is still, the higher parts of the atmosphere move quicker
than those parts which touch the earth, because they are at a greater
distance from the axis of motion. 2. The part of the atmosphere where
the north or south wind comes from is higher than the part of it where
it comes to, hence the more elevated parts of the atmosphere continue to
descend towards the earth as either of those winds approach. 3. When
southern air is brought to us it possesses a westerly direction also,
owing to the velocity it had previously acquired from the earth's
surface; and if it consists of air from the higher parts of the
atmosphere descending nearer the earth, this westerly velocity becomes
increased. But when northern air is brought to us, it possesses an
apparent easterly direction also, owing to the velocity which it had
previously acquired from the earth's surface being less than that of the
earth's surface in this latitude; now if the north-east wind consists of
air descending from higher parts of the atmosphere, this deficiency of
velocity will be less, in consequence of the same cause, viz. The higher
parts of the atmosphere descending, as the wind approaches, increases
the real velocity of the western winds, and decreases the apparent
velocity of the eastern ones.
_October 22._ Wind changed from south-east to south-west. There is a
popular prognostication that if the wind changes from the north towards
the south passing through the east, it is more likely to continue in the
south, than if it passes through the west, which may be thus accounted
for. If the north-east wind changes to a north-west wind, it shews
either that a part of the northern air descends upon us in a spiral
eddy, or that a superior current of southern air is driven back; but if
a north-east wind be changed into a south-east wind it shews that the
northern air is become retrograde, and that in a day or two, as soon as
that part of it has passed, which has not gained the velocity of the
earth's surface in this latitude, it will become a south wind for a few
hours, and then a south-west wind.
The writer of this imperfect sketch of anemology wishes it may incite
some person of greater leizure and ability to attend to this subject,
and by comparing the various meteorological journals and observations
already published, to construct a more accurate and methodical treatise
on this interesting branch of philosophy.
NOTE XXXIV.--VEGETABLE PERSPIRATION.
_And wed the enamoured Oxygene to Light._
CANTO IV. l. 34.
When points or hairs are put into spring-water, as in the experiments of
Sir B. Thompson, (Philos. Trans. Vol. LXXVII.) and exposed to the light
of the sun, much air, which loosely adhered to the water, rises in
bubbles, as explained in note on Fucus, Vol. II. A still greater
quantity of air, and of a purer kind, is emitted by Dr. Priestley's
green matter, and by vegetable leaves growing in water in the sun-shine,
according to Mr. Ingenhouze's experiments; both which I suspect to be
owing to a decomposition of the water perspired by the plant, for the
edge of a capillary tube of great tenuity may be considered as a circle
of points, and as the oxygene, or principle of vital air, may be
expanded into a gas by the sun's light; the hydrogene or inflammable air
may be detained in the pores of the vegetable.
Hence plants growing in the shade are white, and become green by being
exposed to the sun's light; for their natural colour being blue, the
addition of hydrogene adds yellow to this blue, and _tans_ them green. I
suppose a similar circumstance takes place in animal bodies; their
perspirable matter as it escapes in the sun-shine becomes decomposed by
the edges of their pores as in vegetables, though in less quantity, as
their perspiration is less, and by the hydrogene being retained the skin
becomes _tanned_ yellow. In proof of this it must be observed that both
vegetable and animal substances become bleached white by the sun-beams
when they are dead, as cabbage-stalks, bones, ivory, tallow, bees-wax,
linen and cotton cloth; and hence I suppose the copper-coloured natives
of sunny countries might become etiolated or blanched by being kept from
their infancy in the dark, or removed for a few generations to more
northerly climates.
It is probable that on a sunny morning much pure air becomes separated
from the dew by means of the points of vegetables on which it adheres,
and much inflammable air imbibed by the vegetable, or combined with it;
and by the sun's light thus decomposing water the effects of it in
bleaching linen seems to depend (as described in Note X.): the water is
decomposed by the light at the ends or points of the cotton or thread,
and the vital air unites with the phlogistic or colouring matters of the
cloth, and produces a new acid, which is either itself colourless or
washes out, at the same time the inflammable part of the water escapes.
Hence there seems a reason why cotton bleaches so much sooner than
linen, viz. because its fibres are three or four times shorter, and
therefore protrude so many more points, which seem to facilitate the
liberation of the vital air from the inflammable part of the water.
Bee's wax becomes bleached by exposure to the sun and dews in a similar
manner as metals become calcined or rusty, viz. by the water on their
surface being decomposed; and hence the inflammable material which
caused the colour becomes united with vital air forming a new acid, and
is washed away.
Oil close stopped in a phial not full, and exposed long to the sun's
light, becomes bleached, as I suppose, by the decomposition of the water
it contains; the inflammable air rising above the surface, and the vital
air uniting with the colouring matter of the oil. For it is remarkable,
that by shutting up a phial of bleached oil in a dark drawer, it in a
little time becomes coloured again.
The following experiment shews the power of light in separating vital
air from another basis, viz. from azote. Mr. Scheel inverted a glass
vessel filled with colourless nitrous acid into another glass containing
the same acid, and on exposing them to the sun's light, the inverted
glass became partly filled with pure air, and the acid at the same time
became coloured. Scheel in Crell's Annal. 1786. But if the vessel of
colourless nitrous acid be quite full and stopped, so that no space is
left for the air produced to expand itself into, no change of colour
takes place. Priestley's Exp. VI. p. 344. See Keir's very excellent
Chemical Dictionary, p. 99. new edition.
A sun-flower three feet and half high according to the experiment of Dr.
Hales, perspired two pints in one day (Vegetable Statics.) which is many
times as much in proportion to its surface, as is perspired from the
surface and lungs of animal bodies; it follows that the vital air
liberated from the surfaces of plants by the sunshine must much exceed
the quantity of it absorbed by their respiration, and that hence they
improve the air in which they live during the light part of the day, and
thus blanched vegetables will sooner become _tanned into green_ by the
sun's light, than etiolated animal bodies will become _tanned yellow_ by
the same means.
It is hence evident, that the curious discovery of Dr. Priestley, that
his green vegetable matter and other aquatic plants gave out vital air
when the sun shone upon them, and the leaves of other plants did the
same when immersed in water, as observed by Mr. Ingenhouze, refer to the
perspiration of vegetables not to their respiration. Because Dr.
Priestley observed the pure air to come from both sides of the leaves
and even from the stalks of a water-flag, whereas one side of the leaf
only serves the office of lungs, and certainly not the stalks. Exper. on
Air, Vol. III. And thus in respect to the circumstance in which plants
and animals seemed the furtherest removed from each other, I mean in
their supposed mode of respiration, by which one was believed to purify
the air which the other had injured, they seem to differ only in degree,
and the analogy between them remains unbroken.
Plants are said by many writers to grow much faster in the night than in
the day; as is particularly observable in seedlings at their rising out
of the ground. This probably is a consequence of their sleep rather than
of the absence of light; and in this I suppose they also resemble animal
bodies.
NOTE XXXV.--VEGETABLE PLACENTATION.
_While in bright veins the silvery sap ascends.
CANTO IV. l. 419.
As buds are the viviparous offspring of vegetables, it becomes necessary
that they should be furnished with placental vessels for their
nourishment, till they acquire lungs or leaves for the purpose of
elaborating the common juices of the earth into nutriment. These vessels
exist in bulbs and in seeds, and supply the young plant with a sweet
juice till it acquires leaves, as is seen in converting barley into
malt, and appears from the sweet taste of onions and potatoes, when they
begin to grow.
The placental vessels belonging to the buds of trees are placed about
the roots of most, as the vine; so many roots are furnished with sweet
or mealy matter as fern-root, bryony, carrot, turnip, potatoe, or in the
alburnum or sap-wood as in those trees which produce manna, which is
deposited about the month of August, or in the joints of sugar cane, and
grasses; early in the spring the absorbent mouths of these vessels drink
up moisture from the earth, with a saccharine matter lodged for that
purpose during the preceding autumn, and push this nutritive fluid up
the vessels of the alburnum to every individual bud, as is evinced by
the experiments of Dr. Hales, and of Mr. Walker in the Edinburgh
Philosophical Transact. The former observed that the sap from the stump
of a vine, which he had cut off in the beginning of April, arose twenty-
one feet high in tubes affixed to it for that purpose, but in a few
weeks it ceased to bleed at all, and Dr. Walker marked the progress of
the ascending sap, and found likewise that as soon as the leaves became
expanded the sap ceased to rise; the ascending juice of some trees is so
copious and so sweet during the sap-season that it is used to make wine,
as the birch, betula, and sycamore, acer pseudo-platinus, and
particularly the palm.
During this ascent of the sap-juice each individual leaf-bud expands its
new leaves, and shoots down new roots, covering by their intertexture
the old bark with a new one; and as soon as these new roots (or bark)
are capable of absorbing sufficient juices from the earth for the
support of each bud, and the new leaves are capable of performing their
office of exposing these juices to the influence of the air; the
placental vessels cease to act, coalesce, and are transformed from sap-
wood, or alburnum, into inert wood; serving only for the support of the
new tree, which grows over them.
Thus from the pith of the new bud of the horse-chesnut five vessels pass
out through the circle of the placental vessels above described, and
carry with them a minuter circle of those vessels; these five bundles of
vessels unite after their exit, and form the footstalk or petiole of the
new five-fingered leaf, to be spoken of hereafter. This structure is
well seen by cutting off a leaf of the horse-chesnut (Aesculus
Hippocastanum) in September before it falls, as the buds of this tree
are so large that the flower may be seen in them with the naked eye.
After a time, perhaps about midsummer, another bundle of vessels passes
from the pith through the alburnum or sap-vessels in the bosom of each
leaf, and unites by the new bark with the leaf, which becomes either a
flower-bud or a leaf-bud to be expanded in the ensuing spring, for which
purpose an apparatus of placental vessels are produced with proper
nutriment during the progress of the summer and autumn, and thus the
vegetable becomes annually increased, ten thousand buds often existing
on one tree, according to the estimate of Linneus. Phil. Bot.
The vascular connection of vegetable buds with the leaves in whose
bosoms they are formed is confirmed by the following experiment, (Oct.
20, 1781.) On the extremity of a young bud of the Mimosa (sensitive
plant) a small drop of acid of vitriol was put by means of a pen, and,
after a few seconds, the leaf in whose axilla it dwelt closed and opened
no more, though the drop of vitriolic acid was so small as apparently
only to injure the summit of the bud. Does not this seem to shew that
the leaf and its bud have connecting vessels though they arise at
different times and from different parts of the medulla or pith? And, as
it exists previously to it, that the leaf is the parent of the bud?
This placentation of vegetable buds is clearly evinced from the
sweetness of the rising sap, and from its ceasing to rise as soon as the
leaves are expanded, and thus compleats the analogy between buds and
bulbs. Nor need we wonder at the length of the umbilical cords of buds
since that must correspond with their situation on the tree, in the same
manner as their lymphatics and arteries are proportionally elongated.
It does not appear probable that any umbilical artery attends these
placental absorbents, since, as there seems to be no system of veins in
vegetables to bring back the blood from the extremities of their
arteries, (except their pulmonary veins,) there could not be any
vegetable fluids to be returned to their placenta, which in vegetables
seems to be simply an organ for nutrition, whereas the placenta of the
animal foetus seems likewise to serve as a respiratory organ like the
gills of fishes.
NOTE XXXVI--VEGETABLE CIRCULATION.
_And refluent blood in milky eddies bends._
CANTO IV. l. 420.
The individuality of vegetable buds was spoken of before, and is
confirmed by the method of raising all kinds of trees by Mr. Barnes.
(Method of propagating Fruit Trees. 1759. Lond. Baldwin.) He cut a
branch into as many pieces as there were buds or leaves upon it, and
wiping the two wounded ends dry he quickly applied to each a cement,
previously warmed a little, which consisted principally of pitch, and
planted them in the earth. The use of this cement I suppose to consist
in its preventing the bud from bleeding to death, though the author
ascribes it to its antisceptic quality.
These buds of plants, which are thus each an individual vegetable, in
many circumstances resemble individual animals, but as animal bodies are
detached from the earth, and move from place to place in search of food,
and take that food at considerable intervals of time, and prepare it for
their nourishiment within their own bodies after it is taken, it is
evident they must require many organs and powers which are not necessary
to a stationary bud. As vegetables are immoveably fixed to the soil from
whence they draw their nourishment ready prepared, and this uniformly
not at returning intervals, it follows that in examining their anatome
we are not to look for muscles of locomotion, as arms and legs; nor for
organs to receive and prepare their nourishment, as a stomach and
bowels; nor for a reservoir for it after it is prepared, as a general
system of veins, which in locomotive animals contains and returns the
superfluous blood which is left after the various organs of secretion
have been supplied, by which contrivance they are enabled to live a long
time without new supplies of food.
The parts which we may expert to find in the anatome of vegetables
correspondent to those in the animal economy are, 1. A system of
absorbent vessels to imbibe the moisture of the earth similar to the
lacteal vessels, as in the roots of plants; and another system of
absorbents similar to the lymphatics of animal bodies, opening its
mouths on the internal cells and external surfaces of vegetables; and a
third system of absorbent vessels correspondent with those of the
placentation of the animal foetus. 2. A pulmonary system correspondent
to the lungs or gills of quadrupeds and fish, by which the fluid
absorbed by the lacteals and lymphatics may be exposed to the influence
of the air, this is done by the green leaves of plants, those in the air
resembling lungs, and those in the water resembling gills; and by the
petals of flowers. 3. Arterial systems to convey the fluid thus
elaborated to the various glands of the vegetable for the purposes of
its growth, nutrition, and various secretions. 4. The various glands
which separate from the vegetable blood the honey, wax, gum, resin,
starch, sugar, essential oil, &c. 5. The organs adapted for their
propagation or reproduction. 6. Muscles to perform several motions of
their parts.
I. The existence of that branch of the absorbent vessels of vegetables
which resembles the lacteals of animal bodies, and imbibes their
nutriment from the moist earth, is evinced by their growth so long as
moisture is applied to their roots, and their quickly withering when it
is withdrawn.
Besides these absorbents in the roots of plants there are others which
open their mouths on the external surfaces of the bark and leaves, and
on the internal surfaces of all the cells, and between the bark and the
alburnum or sap-wood; the existence of these is shewn, because a leaf
plucked off and laid with its under side on water will not wither so
soon as if left in the dry air,--the same if the bark alone of a branch
which is separated from a tree be kept moist with water,--and lastly, by
moistening the alburnum or sap-wood alone of a branch detached from a
tree it will not so soon wither as if left in the dry air. By the
following experiment these vessels were agreeably visible by a common
magnifying glass, I placed in the summer of 1781 the footstalks of some
large fig-leaves about an inch deep in a decoction of madder, (rubia
tinctorum,) and others in a decoction of logwood, (haematoxylum
campechense,) along with some sprigs cut off from a plant of picris,
these plants were chosen because their blood is white, after some hours,
and on the next day, on taking out either of these and cutting off from
its bottom about a quarter of an inch of the stalk an internal circle of
red points appeared, which were the ends of absorbent vessels coloured
red with the decoction, while an external ring of arteries was seen to
bleed out hastily a milky juice, and at once evinced both the absorbent
and arterial system. These absorbent vessels have been called by Grew,
and Malphigi, and some other philosophers, bronchi, and erroneously
supposed to be air-vessels. It is probable that these vessels, when cut
through, may effuse their fluids, and receive air, their sides being too
stiff to collapse; since dry wood emits air-bubles in the exhausted
receiver in the same manner as moist wood.
The structure of these vegetable absorbents consists of a spiral line,
and not of a vessel interrupted with valves like the animal lymphatics,
since on breaking almost any tender leaf and drawing out some of the
fibres which adhere longest this spiral structure becomes visible even
to the naked eye, and distinctly so by the use of a common lens. See
Grew, Plate 51.
In such a structure it is easy to conceive how a vermicular or
peristaltic motion of the vessel beginning at the lowest part of it,
each spiral ring successively contracting itself till it fills up the
tube, must forcibly push forwards its contents, as from the roots of
vines in the bleeding season; and if this vermicular motion should begin
at the upper end of the vessel it is as easy to see how it must carry
its contained fluid in a contrary direction. The retrograde motion of
the vegetable absorbent vessels is shewn by cutting a forked branch from
a tree, and immersing a part of one of the forks in water, which will
for many days prevent the other from withering; or it is shewn by
planting a willow branch with the wrong end upwards. This structure in
some degree obtains in the esophagus or throat of cows, who by similar
means convey their food first downwards and afterward upwards by a
retrograde motion of the annular muscles or cartilages for the purpose
of a second mastication of it.
II. The fluids thus drank up by the vegetable absorbent vessels from the
earth, or from the atmosphere, or from their own cells and interfaces,
are carried to the foot-stalk of every leaf, where the absorbents
belonging to each leaf unite into branches, forming so many pulmonary
arteries, and are thence dispersed to the extremities of the leaf, as
may be seen in cutting away slice after slice the footstalk of a horse-
chesnut in September before the leaf falls. There is then a compleat
circulation in the leaf; a pulmonary vein receiving the blood from the
extremities of each artery on the upper side of the leaf, and joining
again in the footstalk of the leaf these veins produce so many arteries,
or aortas, which disperse the new blood over the new bark, elongating
its vessels, or producing its secretions; but as a reservoir of blood
could not be wanted by a vegetable bud which takes in its nutriment at
all times, I imagine there is no venous system, no veins properly so
called, which receive the blood which was to spare, and return it into
the pulmonary or arterial system.
The want of a system of veins was countenanced by the following
experiment; I cut off several stems of tall spurge, (Euphorbia
helioscopia) in autumn, about the centre of the plant, and observed
tenfold the quantity of milky juice ooze from the upper than from the
lower extremity, which could hardly have happened if there had been a
venous system of vessels to return the blood from the roots to the
leaves.
Thus the vegetable circulation, complete in the lungs, but probably in
the other part of the system deficient in respect to a system of
returning veins, is carried forwards without a heart, like the
circulation through the livers of animals where the blood brought from
the intestines and mesentery by one vein is dispersed through the liver
by the vena portarum, which assumes the office of an artery. See Note
XXXVII.
At the same time so minute are the vessels in the intertexture of the
barks of plants, which belong to each individual bud, that a general
circulation may possibly exist, though we have not yet been able to
discover the venous part of it.
There is however another part of the circulation of vegetable juices
visible to the naked eye, and that is in the corol or petals of flowers,
in which a part of the blood of the plant is exposed to the influence of
the air and light in the same manner as in the foliage, as will be
mentioned more at large in Notes XXXVII and XXXIX.
These circulations of their respective fluids seem to be carried on in
the vessels of plants precisely as in animal bodies by their
irritability to the stimulus of their adapted fluids, and not by any
mechanical or chemical attraction, for their absorbent vessels propel
the juice upwards, which they drink up from the earth, with great
violence; I suppose with much greater than is exerted by the lacteals of
animals, probably owing to the greater minuteness of these vessels in
vegetables and the greater rigidity of their coats. Dr. Hales in the
spring season cut off a vine near the ground, and by fixing tubes on the
remaining stump of it, found the sap to rise twenty-one feet in the tube
by the propulsive power of these absorbents of the roots of it. Veget.
Stat. p. 102. Such a power can not be produced by capillary attraction,
as that could only raise a fluid nearly to the upper edge of the
attracting cylinder, but not enable it to flow over that edge, and much
less to rise 21 feet above it. What then can this power be owing to?
Doubtless to the living activity of the absorbent vessels, and to their
increased vivacity from the influence of the warmth of the spring
succeeding the winter's cold, and their thence greater susceptibility to
irritation from the juices which they absorb, resembling in all
circumstances the action of the living vessels of animals.
NOTE XXXVII--VEGETABLE RESPIRATION.
_While spread in air the leaves respiring play._
CANTO IV. l. 421.
I. There have been various opinions concerning the use of the leaves of
plants in the vegetable oeconomy. Some have contended that they are
perspiratory organs; this does not seem probable from an experiment of
Dr. Hales, Veg. Stat. p. 30. He found by cutting off branches of trees
with apples on them, and taking off the leaves, that an apple exhaled
about as much as two leaves, the surfaces of which were nearly equal to
the apple; whence it would appear that apples have as good a claim to be
termed perspiratory organs as leaves. Others have believed them
excretory organs of excrementious juices; but as the vapour exhaled from
vegetables has no taste, this idea is no more probable than the other;
add to this that in moist weather, they do not appear to perspire or
exhale at all.
The internal surface of the lungs or air-vessels in men, are said to be
equal to the external surface of the whole body, or about fifteen square
feet; on this surface the blood is exposed to the influence of the
respired air through the medium however of a thin pellicle; by this
exposure to the air it has its colour changed from deep red to bright
scarlet, and acquires something so necessary to the existence of life,
that we can live scarcely a minute without this wonderful process.
The analogy between the leaves of plants and the lungs or gills of
animals seems to embrace so many circumstances, that we can scarcely
withhold our assent to their performing similar offices.
I. The great surface of the leaves compared to that of the trunk and
branches of trees is such, that it would seem to be an organ well
adapted for the purpose of exposing the vegetable juices to the
influence of the air; this however we shall see afterwards is probably
performed only by their upper surfaces, yet even in this case the
surface of the leaves in general bear a greater proportion to the
surface of the tree, than the lungs of animals to their external
surfaces.
2. In the lungs of animal, the blood after having been exposed to the
air in the extremities of pulmonary artery, is changed in colour from
deep red to bright scarlet, and certainly in some of its essential
properties; it is then collected by the pulmonary vein and returned to
the heart. To shew a similarity of circumstance in the leaves of plants
the following experiment was made, June 24, 1781: A stalk with leaves
and seed-vessels of large spurge (Euphorbia helioscopia) had been
several days placed in a decoction of madder (Rubia tinctorum) so that
the lower part of the stem, and two of the undermost leaves were
immersed in it. After having washed the immersed leaves in clear water,
I could readily discern the colour of the madder passing along the
middle rib of each leaf. This red artery was beautifully visible both on
the under and upper surface of the leaf; but on the upper side many red
branches were seen going from it to the extremities of the leaf, which
on the other side were not visible except by looking through it against
the light. On this under side a system of branching vessels carrying a
pale milky fluid were seen coming from the extremities of the leaf, and
covering the whole underside of it, and joining into two large veins,
one on each side of the red artery in the middle rib of the leaf, and
along with it descending to the footstalk or petiole. On slitting one of
these leaves with scissars, and having a common magnifying lens ready,
the milky blood was seen oozing out of the returning veins on each side
of the red artery in the middle rib, but none of the red fluid from the
artery.
All these appearances were more easily seen in a leaf of Picris treated
in the same manner; for in this milky plant the stems and middle rib of
the leaves are sometimes naturally coloured reddish, and hence the
colour of the madder seemed to pass further into the ramifications of
their leaf-arteries, and was there beautifully visible with the
returning branches of milky veins on each side.
3. From these experiments the upper surface of the leaf appeared to be
the immediate organ of respiration, because the coloured fluid was
carried to the extremities of the leaf by vessels most conspicuous on
the upper surface, and there changed into a milky fluid, which is the
blood of the plant, and then returned by concomitant veins on the under
surface, which were seen to ooze when divided with scissars, and which
in Picris, particularly render the under surface of the leaves greatly
whiter than the upper one.
4. As the upper surface of leaves constitutes the organ of respiration,
on which the sap is exposed in the terminations of arteries beneath a
thin pellicle to the action of the atmosphere, these surfaces in many
plants strongly repel moisture, as cabbage-leaves, whence the particles
of rain lying over their surfaces without touching them, as observed by
Mr. Melville (Essays Literary and Philosop. Edinburgh) have the
appearance of globules of quicksilver. And hence leaves laid with the
upper surfaces on water, wither as soon as in the dry air, but continue
green many days, if placed with the under surfaces on water, as appears
in the experiments of Mons. Bonnet (Usage des Fevilles.) Hence some
aquatic plants, as the Water-lily (Nymphoea) have the lower sides of
their leaves floating on the water, while the upper surfaces remain dry
in the air.
5. As those insects, which have many spiracula, or breathing apertures,
as wasps and flies, are immediately suffocated by pouring oil upon
them, I carefully covered with oil the surfaces of several leaves of
Phlomis, of Portugal Laurel, and Balsams, and though it would not
regularly adhere, I found them all die in a day or two.
Of aquatic leaves, see Note on Trapa and on Fucus, in Vol. II. to which
must be added that many leaves are furnished with muscles about their
footstalks, to turn their upper surfaces to the air or light, as Mimosa
and Hedysarum gyrans. From all these analogies I think there can be no
doubt but that leaves of trees are their lungs, giving out a phlogistic
material to the atmosphere, and absorbing oxygene or vital air.
6. The great use of light to vegetation would appear from this theory to
be by disengaging vital air from the water which they perspire, and
thence to facilitate its union with their blood exposed beneath the thin
surface of their leaves; since when pure air is thus applied, it is
probable, that it can be more readily absorbed. Hence in the curious
experiments of Dr. Priestley and Mr. Ingenhouze, some plants purified
air less than others, that is, they perspired less in the sunshine; and
Mr. Scheele found that by putting peas into water, which about half-
covered them, that they converted the vital air into fixed air, or
carbonic acid gas, in the same manner as in animal respiration. See Note
XXXIV.
7. The circulation in the lungs or leaves of plants is very similar to
that of fish. In fish the blood after having passed through their gills
does not return to the heart as from the lungs of air-breathing animals,
but the pulmonary vein taking the structure of an artery after having
received the blood from the gills, which there gains a more florrid
colour, distributes it to the other parts of their bodies. The same
structure occurs in the livers of fish, whence we see in those animals
two circulations independent of the power of the heart, viz. that
beginning at the termination of the veins of the gills, and branching
through the muscles; and that which passes through the liver; both which
are carried on by the action of those respective arteries and veins.
Monro's Physiology of Fish, p. 19.
The course of the fluids in the roots, leaves, and buds of vegetables
seems to be performed in a manner similar to both these. First the
absorbent vessels of the roots and surfaces unite at the footstalk of
the leaf; and then, like the Vena Portarum, an artery commences without
the intervention of a heart, and spreads the sap in its numerous
ramifications on the upper surface of the leaf; here it changes its
colour and properties, and becomes vegetable blood; and is again
collected by a pulmonary vein on the under surface of the leaf. This
vein, like that which receives the blood from the gills of fish, assumes
the office and name of an artery, and branching again disperses the
blood upward to the bud from the footstalk of the leaf, and downward to
the roots; where it is all expended in the various secretions, the
nourishment and growth of the plant, as fast as it is prepared.
II. The organ of respiration already spoken of belongs particularly to
the shoots or buds, but there is another pulmonary system, perhaps
totally independent of the green foliage, which belongs to the
fructification only, I mean the corol or petals. In this there is an
artery belonging to each petal, which conveys the vegetable blood to its
extremities, exposing it to the light and air under a delicate membrane
covering the internal surface of the petal, where it often changes its
colour, as is beautifully seen in some party-coloured poppies; though it
is probable some of the iridescent colours of flowers may be owing to
the different degrees of tenuity of the exterior membrane of the leaf
refracting the light like soap-bubbles, the vegetable blood is then
returned by correspondent vegetable veins, exactly as in the green
foliage; for the purposes of the important secretions of honey, wax, the
finer essential oil, and the prolific dust of the anthers.
1. The vascular structure of the corol as above described, and which is
visible to the naked eye, and its exposing the vegetable juices to the
air and light during the day, evinces that it is a pulmonary organ.
2. As the glands which produce the prolific dust of the anthers, the
honey, wax, and frequently some odoriferous essential oil, are generally
attached to the corol, and always fall off and perish with it, it is
evident that the blood is elaborated or oxygenated in this pulmonary
system for the purpose of these important secretions.
3. Many flowers, as the Colchicum, and Hamamelis arise naked in autumn,
no green leaves appearing till the ensuing spring; and many others put
forth their flowers and complete their impregnation early in the spring
before the green foliage appears, as Mezereon, cherries, pears, which
shews that these corols are the lungs belonging to the fructification.
4. This organ does not seem to have been necessary for the defence of
the stamens and pistils, since the calyx of many flowers, as Tragopogon,
performs this office; and in many flowers these petals themselves are so
tender as to require being shut up in the calyx during the night, for
what other use then can such an apparatus of vessels be designed?
5. In the Helleborus-niger, Christmas-rose, after the seeds are grown to
a certain size, the nectaries and stamens drop off, and the beautiful
large white petals change their colour to a deep green, and gradually
thus become a calyx inclosing and defending the ripening seeds, hence it
would seem that the white vessels of the corol served the office of
exposing the blood to the action of the air, for the purposes of
separating or producing the honey, wax, and prolific dust, and when
these were no longer wanted, that these vessels coalesced like the
placental vessels of animals after their birth, and thus ceased to
perform that office and lost at the same time their white colour. Why
should they loose their white colour, unless they at the same time lost
some other property besides that of defending the seed-vessel, which
they still continue to defend?
6. From these observations I am led to doubt whether green leaves be
absolutely necessary to the progress of the fruit-bud after the last
year's leaves are fallen off. The green leaves serve as lungs to the
shoots and foster the new buds in their bosoms, whether these buds be
leaf-buds or fruit-buds; but in the early spring the fruit-buds expand
their corols, which are their lungs, and seem no longer to require green
leaves; hence the vine bears fruit at one joint without leaves, and puts
out a leaf-bud at another joint without fruit. And I suppose the green
leaves which rise out of the earth in the spring from the Colchicum are
for the purpose of producing the new bulb, and its placenta, and not for
the giving maturity to the seed. When currant or goosberry trees lose
their leaves by the depredation of insects the fruit continues to be
formed, though less sweet and less in size.
7. From these facts it appears that the flower-bud after the corol falls
off, (which is its lungs,) and the stamens and nectary along with it,
becomes simply an uterus for the purpose of supplying the growing
embryon with nourishment, together with a system of absorbent vessels
which bring the juices of the earth to the footstalk of the fruit, and
which there changes into an artery for the purpose of distributing the
sap for the secretion of the saccharine or farinaceous or acescent
materials for the use of the embryon. At the same time as all the
vessels of the different buds of trees inosculate or communicate with
each other, the fruit becomes sweeter and larger when the green leaves
continue on the tree, but the mature flowers themselves, (the succeeding
fruit not considered) perhaps suffer little injury from the green leaves
being taken off, as some florists have observed.
8. That the vessels of different vegetable buds inosculate in various
parts of their circulation is rendered probable by the increased growth
of one bud, when others in its vicinity are cut away; as it thus seems
to receive the nourishment which was before divided amongst many.
NOTE XXXVIII.--VEGETABLE IMPREGNATION.
_Love out their hour and leave their lives in air._
CANTO IV. l. 456.
From the accurate experiments and observations of Spallanzani it appears
that in the Spartium Junceum, rush-broom, the very minute seeds were
discerned in the pod at least twenty days before the flower is in full
bloom, that is twenty days before fecundation. At this time also the
powder of the anthers was visible, but glued fast to their summits. The
seeds however at this time, and for ten days after the blossom had
fallen off, appeared to consist of a gelatinous substance. On the
eleventh day after the falling of the blossom the seeds became heart-
shape, with the basis attached by an appendage to the pod, and a white
point at the apex; this white point was on pressure found to be a cavity
including a drop of liquor.
On the 25th day the cavity which at first appeared at the apex was much
enlarged and still full of liquor, it also contained a very small semi-
transparent body, of a yellowish colour, gelatinous, and fixed by its
two opposite ends to the sides of the cavity.
In a month the seed was much enlarged and its shape changed from a heart
to a kidney, the little body contained in the cavity was increased in
bulk and was less transparent, and gelatinous, but there yet appeared no
organization.
On the 40th day the cavity now grown larger was quite filled with the
body, which was covered with a thin membrane; after this membrane was
removed the body appeared of a bright green, and was easily divided by
the point of a needle into two portions, which manifestly formed the two
lobes, and within these attached to the lower part the exceedingly small
plantule was easily perceived.
The foregoing observations evince, 1. That the seeds exist in the
ovarium many days before fecundation. 2. That they remain for some time
solid, and then a cavity containing a liquid is formed in them. 3. That
after fecundation a body begins to appear within the cavity fixed by two
points to the sides, which in process of time proves to be two lobes
containing a plantule. 4. That the ripe seed consists of two lobes
adhering to a plantule, and surrounded by a thin membrane which is
itself covered with a husk or cuticle. Spalanzani's Dissertations, Vol.
II. p. 253.
The analogy between seeds and eggs has long been observed, and is
confirmed by the mode of their production. The egg is known to be formed
within the hen long before its impregnation; C.F. Wolf asserts that the
yolk of the egg is nourished by the vessels of the mother, and that it
has from those its arterial and venous branches, but that after
impregnation these vessels gradually become impervious and obliterated,
and that new ones are produced from the fetus and dispersed into the
yolk. Haller's Physiolog. Tom. VIII. p. 94. The young seed after
fecundation, I suppose, is nourished in a similar manner from the
gelatinous liquor, which is previously deposited for that purpose; the
uterus of the plant producing or secreting it into a reservoir or amnios
in which the embryon is lodged, and that the young embryon is furnished
with vessels to absorb a part of it, as in the very early embryon in the
animal uterus.
The spawn of frogs and of fish is delivered from the female before its
impregnation. M. Bonnet says that the male salamander darts his semen
into the water, where it forms a little whitish cloud which is
afterwards received by the swoln anus of the female, and she is
fecundated.--He adds that marine plants approach near to these animals,
as the male does not project a fine powder but a liquor which in like
manner forms a little cloud in the water.--And further adds, who knows
but the powder of the stamina of certain plants may not make some
impression on certain germs belonging to the animal kingdom! Letter
XLIII. to Spalanzani, Oevres Philos.
Spalanzani found that the seminal fluid of frogs and dogs even when
diluted with much water retained its prolific quality. Whether this
quality be simply a stimulus exciting the egg into animal action, which
may be called a vivifying principle, or whether part of it be actually
conjoined with the egg is not yet determined, though the latter seems
more probable from the frequent resemblance of the fetus to the male
parent. A conjunction however of both the male and female influence
seems necessary for the purpose of reproduction throughout all organized
nature, as well in hermaphrodite insects, microscopic animals, and
polypi, and exists as well in the formation of the buds of vegetables as
in the production of their seeds, which is ingeniously conceived and
explained by Linneus. After having compared the flower to the larva of a
butterfly, confining of petals instead of wings, calyxes instead of
wing-sheaths, with the organs of reproduction, and having shewn the use
of the farina in fecundating the egg or seed, he proceeds to explain the
production of the bud. The calyx of a flower, he says, is an expansion
of the outer bark, the petals proceed from the inner bark or rind, the
stamens from the alburnum or woody circle, and the style from the pith.
In the production and impregnation of the seed a commixture of the
secretions of the stamens and style are necessary; and for the
production of a bud he thinks the medulla or pith bursts its integuments
and mixes with the woody part or alburnum, and these forcing their
passage through the rind and bark constitute the bud or viviparous
progeny of the vegetable. System of Vegetables translated from Linneus,
p. 8.
It has been supposed that the embryon vegetable after fecundation, by
its living activity or stimulus exerted on the vessels of the parent
plant, may produce the fruit or seed-lobes, as the animal fetus produces
its placenta, and as vegetable buds may be supposed to produce their
umbilical vessels or roots down the bark of the tree. This in respect to
the production of the fruit surrounding the seeds of trees has been
assimilated to the gall-nuts on oak-leaves, and to the bedeguar on
briars, but there is a powerful objection to this doctrine, viz. that
the fruit of figs, all which are female in this country, grow nearly as
large without fecundation, and therefore the embryon has in them no
self-living principle.
NOTE XXXIX.--VEGETABLE GLANDULATION.
_Seeks, where fine pores their dulcet balm distil._
CANTO IV. l. 503.
The glands of vegetables which separate from their blood the mucilage,
starch, or sugar for the placentation or support of their seeds, bulbs,
and buds; or those which deposit their bitter, acrid, or narcotic juices
for their defence from depredations of insects or larger animals; or
those which secrete resins or wax for their protection from moisture or
frosts, consist of vessels too fine for the injection or absorption of
coloured fluids, and have not therefore yet been exhibited to the
inspection even of our glasses, and can therefore only be known by their
effects, but one of the most curious and important of all vegetable
secretions, that of honey, is apparent to our naked eyes, though before
the discoveries of Linneus the nectary or honey-gland had not even
acquired a name.
The odoriferous essential oils of several flowers seem to have been
designed for their defence against the depredations of insects, while
their beautiful colours were a necessary consequence of the size of the
particles of their blood, or of the tenuity of the exterior membrane of
the petal. The use of the prolific dust is now well ascertained, the wax
which covers the anthers prevents this dust from receiving moisture,
which would make it burst prematurely and thence prevent its application
to the stigma, as sometimes happens in moist years and is the cause of
deficient fecundation both of our fields and orchards.
The universality of the production of honey in the vegetable world, and
the very complicated apparatus which nature has constructed in many
flowers, as well as the acrid or deleterious juices she has furnished
those flowers with (as in the Aconite) to protect this honey from rain
and from the depredations of insects, seem to imply that this fluid is
of very great importance in the vegetable economy; and also that it was
necessary to expose it to the open air previous to its reabsorption into
the vegetable vessels.
In the animal system the lachrymal gland separates its fluid into the
open air for the purpose of moistening the eye, of this fluid the part
which does not exhale it absorbed by the puncta lachrymalia and carried
into the nostrils; but as this is not a nutritive fluid the analogy goes
no further than its secretion into the open air and its reabsorption
into the system; every other secreted fluid in the animal body is in
part absorbed again into the system, even those which are esteemed
excrementitious, as the urine and perspirable matter, of which the
latter is secreted, like the honey, into the external air. That the
honey is a nutritious fluid, perhaps the most so of any vegetable
production, appears from its great similarity to sugar, and from its
affording sustenance to such numbers of insects, which live upon it
solely during summer, and lay it up for their winter provision. These
proofs of its nutritive nature evince the necessity of its reabsorption
into the vegetable system for some useful purpose.
This purpose however has as yet escaped the researches of philosophical
botanists. M. Pontedera believes it designed to lubricate the vegetable
uterus, and compares the horn-like nectaries of some flowers to the
appendicle of the caecum intestinum of animals. (Antholog. p. 49.)
Others have supposed that the honey, when reabsorbed, might serve the
purpose of the liquor amnii, or white of the egg, as a nutriment for the
young embryon or fecundated seed in its early state of existence. But as
the nectary is found equally general in male flowers as in female ones;
and as the young embryon or seed grows before the petals and nectary are
expanded, and after they fall off; and, thirdly, as the nectary so soon
falls off after the fecundation of the pistillum; these seem to be
insurmountable objections to both the above-mentioned opinions.
In this state of uncertainty conjectures may be of use so far as they
lead to further experiment and investigation. In many tribes of insects,
as the silk-worm, and perhaps in all the moths and butterflies, the male
and female parents die as soon as the eggs are impregnated and excluded;
the eggs remaining to be perfected and hatched at some future time. The
same thing happens in regard to the male and female parts of flowers;
the anthers and filaments, which constitute the male parts of the
flower, and the stigma and style, which constitute the female part of
the flower, fall off and die as soon as the seeds are impregnated, and
along with these the petals and nectary. Now the moths and butterflies
above-mentioned, as soon as they acquire the passion and the apparatus
for the reproduction of their species, loose the power of feeding upon
leaves as they did before, and become nourished by what?--by honey alone.
Hence we acquire a strong analogy for the use of the nectary or
secretion of honey in the vegetable economy, which is, that the male
parts of flowers, and the female parts, as soon as they leave their
fetus-state, expanding their petals, (which constitute their lungs,)
become sensible to the passion, and gain the apparatus for the
reproduction of their species, and are fed and nourished with honey like
the insects above described; and that hence the nectary begins its
office of producing honey, and dies or ceases to produce honey at the
same time with the birth and death of the stamens and the pistils;
which, whether existing in the same or in different flowers, are
separate and distinct animated beings.
Previous to this time the anthers with their filaments, and the stigmas
with their styles, are in their fetus-state sustained by their placental
vessels, like the unexpanded leaf-bud; with the seeds existing in the
vegetable womb yet unimpregnated, and the dust yet unripe in the cells
of the anthers. After this period they expand their petals, which have
been shewn above to constitute the lungs of the flower; the placental
vessels, which before nourished the anthers and the stigmas, coalesce or
cease to nourish them; and they now acquire blood more oxygenated by the
air, obtain the passion and power of reproduction, are sensible to heat,
and cold, and moisture, and to mechanic stimulus, and become in reality
insects fed with honey, similar in every respect except their being
attached to the tree on which they were produced.
Some experiments I have made this summer by cutting out the nectaries of
several flowers of the aconites before the petals were open, or had
become much coloured, some of these flowers near the summit of the
plants produced no seeds, others lower down produced seeds; but they
were not sufficiently guarded from the farina of the flowers in their
vicinity; nor have I had opportunity to try if these seeds would
vegetate.
I am acquainted with a philosopher, who contemplating this subject
thinks it not impossible, that the first insects were the anthers or
stigmas of flowers; which had by some means loosed themselves from their
parent plant, like the male flowers of Vallisneria; and that many other
insects have gradually in long process of time been formed from these;
some acquiring wings, others fins, and others claws, from their
ceaseless efforts to procure their food, or to secure themselves from
injury. He contends, that none of these changes are more
incomprehensible than the transformation of tadpoles into frogs, and
caterpillars into butterflies.
There are parts of animal bodies, which do not require oxygenated blood
for the purpose of their secretions, as the liver; which for the
production of bile takes its blood from the mesenteric veins, after it
must have lost the whole or a great part of its oxygenation, which it
had acquired in its passage through the lungs. In like manner the
pericarpium, or womb of the flower, continues to secrete its proper
juices for the present nourishment of the newly animated embryon-seed;
and the saccharine, acescent, or starchy matter of the fruit or seed-
lobes for its future growth; in the same manner as these things went on
before fecundation; that is, without any circulation of juices in the
petals, or production of honey in the nectary; these having perished and
fallen off with the male and female apparatus for impregnation.
It is probable that the depredations of insects on this nutritious fluid
must be injurious to the products of vegetation, and would be much more
so, but that the plants have either acquired means to defend their honey
in part, or have learned to make more than is absolutely necessary for
their own economy. In the same manner the honey-dew on trees is very
injurious to them; in which disease the nutritive fluid, the vegetable-
sap-juice, seems to be exsuded by a retrograde motion of the cutaneous
lymphatics, as in the sweating sickness of the last century. To prevent
the depredation of insects on honey a wealthy man in Italy is said to
have poisoned his neighbour's bees perhaps by mixing arsnic with honey,
against which there is a most flowery declamation in Quintilian. No.
XIII. As the use of the wax is to preserve the dust of the anthers from
moisture, which would prematurely burst them, the bees which collect
this for the construction of the combs or cells, must on this account
also injure the vegetation of a country where they too much abound.
It is not easy to conjecture why it was necessary that this secretion of
honey should be exposed to the open air in the nectary or honey-cup, for
which purpose so great an apparatus for its defence from insects and
from showers became necessary. This difficulty increases when we
recollect that the sugar in the joints of grass, in the sugar-cane, and
in the roots of beets, and in ripe fruits is produced without the
exposure to the air. On supposition of its serving for nutriment to the
anthers and stigmas it may thus acquire greater oxygenation for the
purpose of producing greater powers of sensibility, according to a
doctrine lately advanced by a French philosopher, who has endeavoured to
shew that the oxygene, or base of vital air, is the constituent
principle of our power of sensibility.
From this provision of honey for the male and female parts of flowers,
and from the provision of sugar, starch, oil, and mucilage, in the
fruits, seed-cotyledons, roots, and buds of plants laid up for the
nutriment of the expanding fetus, not only a very numerous class of
insects, but a great part of the larger animals procure their food; and
thus enjoy life and pleasure without producing pain to others, for these
seeds or eggs with the nutriment laid up in them are not yet endued with
sensitive life.
The secretions from various vegetable glands hardened in the air produce
gums, resins, and various kinds of saccharine, saponaceous, and wax-like
substances, as the gum of cherry or plumb-trees, gum tragacanth from the
astragalus tragacantha, camphor from the laurus camphora, elemi from
amyris elemifera, aneme from hymenoea courbaril, turpentine from
pistacia terebinthus, balsam of Mecca from the buds of amyris
opobalsamum, branches of which are placed in the temples of the East on
account of their fragrance, the wood is called xylobalsamum, and the
fruit carpobalsamum; aloe from a plant of the same name; myrrh from a
plant not yet described; the remarkably elastic resin is brought into
Europe principally in the form of flasks, which look like black leather,
and are wonderfully elastic, and not penetrable by water, rectified
ether dissolves it; its flexibility is encreased by warmth and destroyed
by cold; the tree which yields this juice is the jatropha elastica, it
grows in Guaiana and the neighbouring tracts of America; its juice is
said to resemble wax in becoming soft by heat, but that it acquires no
elasticity till that property is communicated to it by a secret art,
after which it is poured into moulds and well dried and can no longer be
rendered fluid by heat. Mr. de la Borde physician at Cayenne has given
this account. Manna is obtained at Naples from the fraxinus ornus, or
manna-ash, it partly issues spontaneously, which is preferred, and
partly exsudes from wounds made purposely in the month of August, many
other plants yield manna more sparingly; sugar is properly made from the
saccharum officinale, or sugar-cane, but is found in the roots of beet
and many other plants; American wax is obtained from the myrica
cerifera, candle-berry myrtle, the berries are boiled in water and a
green wax separates, with luke-warm water the wax is yellow: the seed of
croton sebiferum are lodged in tallow; there are many other vegetable
exsudations used in the various arts of dyeing, varnishing, tanning,
lacquering, and which supply the shop of the druggist with medicines and
with poisons.
There is another analogy, which would seem to associate plants with
animals, and which perhaps belongs to this Note on Glandulation, I mean
the similarity of their digestive powers. In the roots of growing
vegetables, as in the process of making malt, the farinaceous part of
the seed is converted into sugar by the vegetable power of digestion in
the same manner as the farinaceous matter of seeds are converted into
sweet chyle by the animal digestion. The sap-juice which rises in the
vernal months from the roots of trees through the alburnum or sap-wood,
owes its sweetness I suppose to a similar digestive power of the
absorbent system of the young buds. This exists in many vegetables in
great abundance as in vines, sycamore, birch, and most abundantly in the
palm-tree, (Isert's Voyage to Guinea,) and seems to be a similar fluid
in all plants, as chyle is similar in all animals.
Hence as the digested food of vegetables consists principally of sugar,
and from that is produced again their mucilage, starch, and oil, and
since animals are sustained by these vegetable productions, it would
seem that the sugar-making process carried on in vegetable vessels was
the great source of life to all organized beings. And that if our
improved chemistry should ever discover the art of making sugar from
fossile or aerial matter without the assistance of vegetation, food for
animals would then become as plentiful as water, and mankind might live
upon the earth as thick as blades of grass, with no restraint to their
numbers but the want of local room.
It would seem that roots fixed in the earth, and leaves innumerable
waving in the air were necessary for the decomposition of water, and the
conversion of it into saccharine matter, which would have been not only
cumberous but totally incompatible with the locomotion of animal bodies.
For how could a man or quadruped have carried on his head or back a
forest of leaves, or have had long branching lacteal or absorbent
vessels terminating in the earth? Animals therefore subsist on
vegetables; that is, they take the matter so far prepared, and have
organs to prepare it further for the purposes of higher animation, and
greater sensibility. In the same manner the apparatus of green leaves
and long roots were found inconvenient for the more animated and
sensitive parts of vegetable-flowers, I mean the anthers and stigmas,
which are therefore separate beings, endued with the passion and power
of reproduction, with lungs of their own, and fed with honey, a food
ready prepared by the long roots and green leaves of the plant, and
presented to their absorbent mouths.
From this outline a philosopher may catch a glimpse of the general
economy of nature; and like the mariner cast upon an unknown shore, who
rejoiced when he saw the print of a human foot upon the sand, he may cry
out with rapture, "A GOD DWELLS HERE."
CONTENTS
OF THE
ADDITIONAL NOTES.
NOTE I ... METEORS.
There are four strata of the atmosphere, and four kinds of meteors. 1.
Lightning is electric, exists in visible clouds, its short course, and
red light. 2. Shooting stars exist in invisible vapour, without sound,
white light, have no luminous trains. 3. Twilight; fire-balls move
thirty miles in a second, and are about sixty miles high, have luminous
trains, occasioned by an electric spark passing between the aerial and
inflammable strata of the atmosphere, and mixing them and setting them
on fire in its passage; attracted by volcanic eruptions; one thousand
miles through such a medium resists less than the tenth of an inch of
glass. 4. Northern lights not attracted to a point but diffused; their
colours; passage of electric fire in vacuo dubious; Dr. Franklin's
theory of northern lights countenanced in part by the supposition of
a superior atmosphere of inflammable air; antiquity of their appearance;
described in Maccabees.
NOTE II ... PRIMARY COLOURS.
The rainbow was in part understood before Sir Isaac Newton; the seven
colours were discovered by him; Mr. Gallon's experiments on colours;
manganese and lead produce colourless glass.
NOTE III ... COLOURED CLOUDS.
The rays refracted by the convexity of the atmosphere; the particles of
air and of water are blue; shadow by means of a candle in the day; halo
round the moon in a fog; bright spot in the cornea of the eye; light
from cat's eyes in the dark, from a horse's eyes in a cavern, coloured
by the choroid coat within the eye.
NOTE IV ... COMETS.
Tails of comets from rarified vapour, like northern lights, from
electricity; twenty millions of miles long; expected comet.
NOTE V ... SUN'S RAYS.
Dispute about phlogiston; the sun the fountain from whence all
phlogiston is derived; its rays not luminous till they arrive at our
atmosphere; light owing to their combustion with air, whence an unknown
acid; the sun is on fire only on its surface; the dark spots on it are
excavations through its luminous crust.
NOTE VI ... CENTRAL FIRES.
Sun's heat much less than that from the fire at the earth's centre;
sun's heat penetrates but a few feet in summer; some mines are warm;
warm springs owing to subterraneous fire; situations of volcanos on high
mountains; original nucleus of the earth; deep vallies of the ocean;
distant perception of earthquakes; great attraction of mountains;
variation of the compass; countenance the existence of a cavity or fluid
lava within the earth.
NOTE VII ... ELEMENTARY HEAT.
Combined and sensible heat; chemical combinations attract heat,
solutions reject heat; ice cools boiling water six times as much as cold
water cools it; cold produced by evaporation; heat by devaporation;
capacities of bodies in respect to heat, 1. Existence of the matter of
heat shewn from the mechanical condensation and rarefaction of air, from
the steam produced in exhausting a receiver, snow from rarefied air,
cold from discharging an air-gun, heat from vibration or friction; 2.
Matter of heat analogous to the electric fluid in many circumstances,
explains many chemical phenomena.
NOTE VIII ... MEMNON'S LYRE.
Mechanical impulse of light dubious; a glass tube laid horizontally
before a fire revolves; pulse-glass suspended on a centre; black leather
contracts in the sunshine; Memnon's statue broken by Cambyses.
NOTE IX ... LUMINOUS INSECTS.
Eighteen species of glow-worm, their light owing to their respiration in
transparent lungs; Acudia of Surinam gives light enough to read and draw
by, use of its light to the insect; luminous sea-insects adhere to the
skin of those who bathe in the ports of Languedoc, the light may arise
from putrescent slime.
NOTE X ... PHOSPHORUS.
Discovered by Kunkel, Brandt, and Boyle; produced in respiration, and by
luminous insects, decayed wood, and calcined shells; bleaching a slow
combustion in which the water is decomposed; rancidity of animal fat
owing to the decomposition of water on its surface; aerated marine acid
does not whiten or bleach the hand.
NOTE XI ... STEAM-ENGINE.
Hero of Alexandria first applied steam to machinery, next a French
writer in 1630, the Marquis of Worcester in 1655, Capt. Savery in 1689,
Newcomen and Cawley added the piston; the improvements of Watt and
Boulton; power of one of their large engines equal to two hundred
horses.
NOTE XII ... FROST.
Expansion of water in freezing; injury done by vernal frosts; fish,
eggs, seeds, resist congelation; animals do not resist the increase of
heat; frosts do not meliorate the ground, nor are in general salubrious;
damp air produces cold on the skin by evaporation; snow less pernicious
to agriculture than heavy rains for two reasons.
NOTE XIII ... ELECTRICITY.
1. _Points_ preferable to knobs for defence of buildings; why points
emit the electric fluid; diffusion of oil on water; mountains are points
on the earth's globe; do they produce ascending currents of air? 2.
_Fairy-rings_ explained; advantage of paring and burning ground.
NOTE XIV ... BUDS AND BULBS.
A tree is a swarm of individual plants; vegetables are either oviparous
or viviparous; are all annual productions like many kinds of insects?
Hybernacula, a new bark annually produced over the old one in trees and
in some herbaceous plants, whence their roots seem end-bitten; all
bulbous roots perish annually; experiment on a tulip-root; both the
leaf-bulbs and the flower-bulbs are annually renewed.
NOTE XV ... SOLAR VOLCANOS.
The spots in the sun are cavities, some of them four thousand miles deep
and many times as broad; internal parts of the sun are not in a state of
combustion; volcanos visible in the sun; all the planets together are
less than one six hundred and fiftieth part of the sun; planets were
ejected from the sun by volcanos; many reasons shewing the probability
of this hypothesis; Mr. Buffon's hypothesis that planets were struck off
from the sun by comets; why no new planets are ejected from the sun;
some comets and the georgium sidus may be of later date; Sun's matter
decreased; Mr. Ludlam's opinion, that it is possible the moon might be
projected from the earth.
NOTE XVI ... CALCAREOUS EARTH.
High mountains and deep mines replete with shells; the earth's nucleus
covered with limestone; animals convert water into limestone; all the
calcareous earth in the world formed in animal and vegetable bodies;
solid parts of the earth increase; the water decreases; tops of
calcareous mountains dissolved; whence spar, marbles, chalk,
stalactites; whence alabaster, fluor, flint, granulated limestone, from
solution of their angles, and by attrition; tupha deposited on moss;
limestones from shells with animals in them; liver-stone from fresh-
water muscles; calcareous earth from land-animals and vegetables, as
marl; beds of marble softened by fire; whence Bath-stone contains lime
as well as limestone.
NOTE XVII ... MORASSES.
The production of morasses from fallen woods; account by the Earl
Cromartie of a new morass; morasses lose their salts by solution in
water; then their iron; their vegetable acid is converted into marine,
nitrous, and vitriolic acids; whence gypsum, alum, sulphur; into fluor-
acid, whence fluor; into siliceous acid, whence flint, the sand of the
sea, and other strata of siliceous sand and marl; some morasses ferment
like new hay, and, subliming their phlogistic part, form coal-beds above
and clay below, which are also produced by elutriation; shell-fish in
some morasses, hence shells sometimes found on coals and over iron-
stone.
NOTE XVIII ... IRON
Calciform ores; combustion of iron in vital air; steel from deprivation
of vital air; welding; hardness; brittleness like Rupert's drops;
specific levity; hardness and brittleness compared; steel tempered by
its colours; modern production of iron, manganese, calamy; septaria of
iron-stone ejected from volcanos; red-hot cannon balls.
NOTE XIX ... FLINT.
1. _Siliceous rocks_ from morasses; their cements. 2. _Siliceous trees_;
coloured by iron or manganese; Peak-diamonds; Bristol-stones; flint in
form of calcareous spar; has been fluid without much heat; obtained from
powdered quartz and fluor-acid by Bergman and by Achard. 3. _Agates and
onyxes_ found in sand-rocks; of vegetable origin; have been in complete
fusion; their concentric coloured circles not from superinduction but
from congelation; experiment of freezing a solution of blue vitriol;
iron and manganese repelled in spheres as the nodule of flint cooled;
circular stains of marl in salt-mines; some flint nodules resemble knots
of wood or roots. 4. _Sand of the sea_; its acid from morasses; its base
from shells. 5. _Chert or petrosilex_ stratified in cooling; their
colour and their acid from sea-animals; labradore-stone from mother-
pearl. 6. _Flints in chalk-beds_; their form, colour, and acid, from the
flesh of sea-animals; some are hollow and lined with crystals; contain
iron; not produced by injection from without; coralloids converted to
flint; French-millstones; flints sometimes found in solid strata. 7.
_Angles of sand_ destroyed by attrition and solution in steam; siliceous
breccia cemented by solution in red-hot water. 8. _Basaltes and
granites_ are antient lavas; basaltes raised by its congelation not by
subterraneous fire.
NOTE XX ... CLAY.
Fire and water two great agents; stratification from precipitation; many
stratified materials not soluble in water. 1. Stratification of lava
from successive accumulation. 2. Stratifications of limestone from the
different periods of time in which the shells were deposited. 3.
Stratifications of coal, and clay, and sandstone, and iron-ores, not
from currents of water, but from the production of morass-beds at
different periods of time; morass-beds become ignited; their bitumen and
sulphur is sublimed; the clay, lime, and iron remain; whence sand,
marle, coal, white clay in valleys, and gravel-beds, and some ochres,
and some calcareous depositions owing to alluviation; clay from
decomposed granite; from the lava of Vesuvius; from vitreous lavas.
NOTE XXI ... ENAMELS.
Rose-colour and purple from gold; precipitates of gold by alcaline salt
preferable to those by tin; aurum fulminans long ground; tender colours
from gold or iron not dissolved but suspended in the glass; cobalts;
calces of cobalt and copper require a strong fire; Ka-o-lin and
Pe-tun-tse the same as our own materials.
NOTE XXII ... PORTLAND VASE.
Its figures do not allude to private history; they represent a part of
the Elusinian mysteries; marriage of Cupid and Psyche; procession of
torches; the figures in one compartment represent MORTAL LIFE in the act
of expiring, and HUMANKIND attending to her with concern; Adam and Eve
hyeroglyphic figures; Abel and Cain other hyeroglyphic figures; on the
other compartment is represented IMMORTAL LIFE, the Manes or Ghost
descending into Elisium is led on by DIVINE LOVE, and received by
IMMORTAL LIFE, and conducted to Pluto; Tree of Life and Knowledge are
emblematical; the figure at the bottom is of Atis, the first great
Hierophant, or teacher of mysteries.
NOTE XXIII ... COAL.
1. A fountain of fossile tar in Shropshire; has been distilled from the
coal-beds beneath, and condensed in the cavities of a sand-rock; the
coal beneath is deprived of its bitumen in part; bitumen sublimed at
Matlock into cavities lined with spar. 2. Coal has been exposed to heat;
woody fibres and vegetable seeds in coal at Bovey and Polesworth; upper
part of coal-beds more bituminous at Beaudesert; thin stratum of
asphaltum near Caulk; upper part of coal-bed worse at Alfreton; upper
stratum of no value at Widdrington; alum at West-Hallum; at Bilston. 3.
Coal at Coalbrooke-Dale has been immersed in the sea, shewn by sea-
shells; marks of violence in the colliery at Mendip and at Ticknal;
Lead-ore and spar in coal-beds; gravel over coal near Lichfield; Coal
produced from morasses shewn by fern-leaves, and bog-shells, and muscle-
shells; by some parts of coal being still woody; from Lock Neagh and
Bovey, and the Temple of the devil; fixed alcali; oil.
NOTE XXIV ... GRANITE.
Granite the lowest stratum of the earth yet known; porphory, trap, Moor-
stone, Whin-stone, slate, basaltes, all volcanic productions dissolved
in red-hot water; volcanos in granite strata; differ from the heat of
morasses from fermentation; the nucleus of the earth ejected from the
sun? was the sun originally a planet? supposed section of the globe.
NOTE XXV ... EVAPORATION.
I. Solution of water in air; in the matter of heat; pulse-glass. 2. Heat
is the principal cause of evaporation; thermometer cooled by evaporation
of ether; heat given from steam to the worm-tub; warmth accompanying
rain. 3. Steam condensed on the eduction of heat; moisture on cold
walls; south-west and north-east winds. 4. Solution of salt and of blue
vitriol in the matter of heat. II. Other vapours may precipitate steam
and form rain. 1. Cold the principal cause of devaporation; hence the
steam dissolved in heat is precipitated, but that dissolved in air
remains even in frosts; south-west wind. 2. North-east winds mixing with
south-west winds produce rain; because the cold particles of air of the
north-east acquire some of the matter of heat from the south-west winds.
3. Devaporation from mechanical expansion of air, as in the receiver of
an air-pump; summer-clouds appear and vanish; when the barometers sink
without change of wind the weather becomes colder. 4. Solution of water
in electric fluid dubious. 5. Barometer sinks from the lessened gravity
of the air, and from the rain having less pressure as it falls; a
mixture of a solution of water in calorique with an aerial solution of
water is lighter than dry air; breath of animals in cold weather why
condensed into visible vapour and dissolved again.
NOTE XXVI ... SPRINGS.
Lowest strata of the earth appear on the highest hills; springs from
dews sliding between them; mountains are colder than plains; 1. from
their being insulated in the air; 2. from their enlarged surface; 3.
from the rarety of the air it becomes a better conductor of heat; 4. by
the air on mountains being mechanically rarefied as it ascends; 5.
gravitation of the matter of heat; 6. the dashing of clouds against
hills; of fogs against trees; springs stronger in hot days with cold
nights; streams from subterranean caverns; from beneath the snow on the
Alps.
NOTE XXVII ... SHELL-FISH.
The armour of the Echinus moveable; holds itself in storms to stones by
1200 or 2000 strings: Nautilus rows and sails; renders its shell
buoyant: Pinna and Cancer; Byssus of the antients was the beard of the
Pinna; as fine as the silk is spun by the silk-worm; gloves made of it;
the beard of muscles produces sickness; Indian weed; tendons of rats
tails.
NOTE XXVIII ... STURGEON.
Sturgeon's mouth like a purse; without teeth; tendrils like worms hang
before his lips, which entice small fish and sea-insects mistaking them
for worms; his skin used for covering carriages; isinglass made from it;
cavear from the spawn.
NOTE XXIX ... OIL ON WATER.
Oil and water do not touch; a second drop of oil will not diffuse itself
on the preceeding one; hence it stills the waves; divers for pearl carry
oil in their mouths; oil on water produces prismatic colours; oiled cork
circulates on water; a phial of oil and water made to oscillate.
NOTE XXX ... SHIP-WORM.
The Teredo has calcareous jaws; a new enemy; they perish when they meet
together in their ligneous canals; United Provinces alarmed for the
piles of the banks of Zeland; were destroyed by a severe winter.
NOTE XXXI ... MAELSTROM.
A whirlpool on the coast of Norway; passes through a subterraneous
cavity; less violent when the tide is up; eddies become hollow in the
middle; heavy bodies are thrown out by eddies; light ones retained; oil
and water whirled in a phial; hurricanes explained.
NOTE XXXII ... GLACIERS.
Snow in contact with the earth is in a state of thaw; ice-houses; rivers
from beneath the snow; rime in spring vanishes by its contact with the
earth; and snow by its evaporation and contact with the earth; moss
vegetates beneath the snow; and Alpine plants perish at Upsal for want
of show.
NOTE XXXIII ... WINDS.
Air is perpetually subject to increase and to diminution; Oxygene is
perpetually produced from vegetables in the sunshine, and from clouds in
the light, and from water; Azote is perpetually produced from animal and
vegetable putrefaction, or combustion; from springs of water; volatile
alcali; fixed alcali; sea-water; they are both perpetually diminished by
their contact with the soil, producing nitre; Oxygene is diminished in
the production of all acids; Azote by the growth of animal bodies;
charcoal in burning consumes double its weight of pure air; every barrel
of red-lead absorbes 2000 cubic feet of vital air; air obtained from
variety of substances by Dr. Priestley; Officina aeris in the polar
circle, and at the Line. _South-west winds_; their westerly direction
from the less velocity of the earth's surface; the contrary in respect
to north-east winds; South-west winds consist of regions of air from the
south; and north-east winds of regions of air from the north; when the
south-west prevails for weeks and the barometer sinks to 28, what
becomes of above one fifteenth part of the atmosphere; 1. It is not
carried back by superior currents; 2. Not from its loss of moisture; 3.
Not carried over the pole; 4. Not owing to atmospheric tides or
mountains; 5. It is absorbed at the polar circle; hence south-west winds
and rain; south-west sometimes cold. _North-east winds_ consist of air
from the north; cold by the evaporation of ice; are dry winds; 1. Not
supplied by superior current; 2. The whole atmosphere increased in
quantity by air set at liberty from its combinations in the polar
circles. _South-east winds_ consist of north winds driven back. _North-
west winds_ consist of south-west winds driven back; north-west winds of
America bring frost; owing to a vertical spiral eddy of air between the
eastern coast and the Apalachian mountains; hence the greater cold of
North America. _Trade-winds_; air over the Line always hotter than at
the tropics; trade-winds gain their easterly direction from the greater
velocity of the earth's surface at the line; not supplied by superior
currents; supplied by decomposed water in the sun's great light; 1.
Because there are no constant rains in the tract of the trade-winds; 2.
Because there is no condensible vapour above three or four miles high at
the line. _Monsoons and tornadoes_; some places at the tropic become
warmer when the sun is vertical than at the line; hence the air ascends,
supplied on one side by the north-east winds, and on the other by the
south-west; whence an ascending eddy or tornado, raising water from the
sea, or sand from the desert, and incessant rains; air diminished to the
northward produces south-west winds; tornadoes from heavier air above
sinking through lighter air below, which rises through a perforation;
hence trees are thrown down in a narrow line of twenty or forty yards
broad, the sea rises like a cone, with great rain and lightning. _Land
and sea breezes_; sea less heated than land; tropical islands more
heated in the day than the sea, and are cooled more in the night.
_Conclusion_; irregular winds from other causes; only two original winds
north and south; different sounds of north-east and south-west winds; a
Bear or Dragon in the arctic circle that swallows at times and
disembogues again above one fifteenth part of the atmosphere; wind-
instruments; recapitulation.
NOTE XXXIV ... VEGETABLE PERSPIRATION.
Pure air from Dr. Priestley's vegetable matter, and from vegetable
leaves, owing to decomposition of water; the hydrogene retained by the
vegetables; plants in the shade are _tanned_ green by the sun's light;
animal skins are _tanned_ yellow by the retention of hydrogene; much
pure air from dew on a sunny morning; bleaching why sooner performed on
cotton than linen; bees wax bleached; metals calcined by decomposition
of water; oil bleached in the light becomes yellow again in the dark;
nitrous acid coloured by being exposed to the sun; vegetables perspire
more than animals, hence in the sun-shine they purify air more by their
perspiration than they injure it by their respiration; they grow fastest
in their sleep.
NOTE XXXV ... VEGETABLE PLACENTATION.
Buds the viviparous offspring of vegetables; placentation in bulbs and
seeds; placentation of buds in the roots, hence the rising of sap in the
spring, as in vines, birch, which ceases as soon as the leaves expand;
production of the leaf of Horse-chesnut, and of its new bud; oil of
vitriol on the bud of Mimosa killed the leaf also; placentation shewn
from the sweetness of the sap; no umbilical artery in vegetables.
NOTE XXXVI ... VEGETABLE CIRCULATION.
Buds set in the ground will grow if prevented from bleeding to death by
a cement; vegetables require no muscles of locomotion, no stomach or
bowels, no general system of veins; they have, 1. Three systems of
absorbent vessels; 2. Two pulmonary systems; 3. Arterial systems; 4.
Glands; 5. Organs of reproduction; 6. muscles. I. Absorbent system
evinced by experiments by coloured absorptions in fig-tree and picris;
called air-vessels erroneously; spiral structure of absorbent vessels;
retrograde motion of them like the throats of cows. II. Pulmonary
arteries in the leaves, and pulmonary veins; no general system of veins
shewn by experiment; no heart; the arteries act like the vena portarum
of the liver; pulmonary system in the petals of flowers; circulation
owing to living irritability; vegetable absorption more powerful than
animal, as in vines; not by capillary attraction.
NOTE XXXVII ... VEGETABLE RESPIRATION.
I. Leaves not perspiratory organs, nor excretory ones; lungs of animals.
1. Great surfaces of leaves. 2. Vegetable blood changes colour in the
leaves; experiment with spurge; with picris. 3. Upper surface of the
leaf only acts as a respiratory organ. 4. Upper surface repels moisture;
leaves laid on water. 5. Leaves killed by oil like insects; muscles at
the foot-stalks of leaves. 6. Use of light to vegetable leaves;
experiments of Priestley, Ingenhouze, and Scheel. 7. Vegetable
circulation similar to that of fish. II. Another pulmonary system
belongs to flowers; colours of flowers. 1. Vascular structure of the
corol. 2. Glands producing honey, wax, &c. perish with the corol. 3.
Many flowers have no green leaves attending them, as Colchicum. 4.
Corols not for the defence of the stamens. 5. Corol of Helleborus Niger
changes to a calyx. 6. Green leaves not necessary to the fruit-bud;
green leaves of Colchicum belong to the new bulb not to the flower. 7.
Flower-bud after the corol falls is simply an uterus; mature flowers not
injured by taking of the green leaves. 8. Inosculation of vegetable
vessels.
NOTE XXXVIII ... VEGETABLE IMPREGNATION.
Seeds in broom discovered twenty days before the flower opens; progress
of the seed after impregnation; seeds exist before fecundation; analogy
between seeds and eggs; progress of the egg within the hen; spawn of
frogs and of fish; male Salamander; marine plants project a liquor not a
powder; seminal fluid diluted with water, if a stimulus only? Male and
female influence necessary in animals, insects, and vegetables, both in
production of seeds and buds; does the embryon seed produce the
surrounding fruit, like insects in gall-nuts?
NOTE XXXIX ... VEGETABLE GLANDULATION.
Vegetable glands cannot be injected with coloured fluids; essential oil;
wax; honey; nectary, its complicate apparatus; exposes the honey to the
air like the lacrymal gland; honey is nutritious; the male and female
parts of flowers copulate and die like moths and butterflies, and are
fed like them with honey; anthers supposed to become insects;
depredation of the honey and wax injurious to plants; honey-dew; honey
oxygenated by exposure to air; necessary for the production of
sensibility; the provision for the embryon plant of honey, sugar,
starch, &c. supplies food to numerous classes of animals; various
vegetable secretions as gum tragacanth, camphor, elemi, anime,
turpentine, balsam of Mecca, aloe, myrrh, elastic resin, manna, sugar,
wax, tallow, and many other concrete juices; vegetable digestion;
chemical production of sugar would multiply mankind; economy of nature.
THE END