John Wesley.

A survey of the wisdom of God in the creation; or, A compendium of natural philosophy .. (Volume 3) online

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the reflection and other phaenomena of light : as also sen-
sation, and muscular motion. Indeed it seems to be the
first spring of all the action in the universe.



141

Air is sometimes deprived of its elasticity, and wrought
into the substance of other bodies, from which never-
theless it may be extracted, and resume its elastic state.
As to animal substances, a very considerable quantity of
air is extracted from them by distillation, not only from
the blood and fat, but also from the most solid parts of
animals. Haifa cubic inch of a fallow deer's horn pro-
duced 117 cubic inches of air; half a cubic inch of
oyster shells no less than l6'2 cubic inches.

As to vegetable substances, half a cubic inch of heart
of oak generated 108 cubic inches : a cubic inch of peas
3$)6 cubic inches, or 113 grains, which was above a third
of its weight. This air will flash if touched with a
caudle.

Camphire generates no air: brandy next to none:,
well-water, or rain-water, a little pynnont-water, twice
as much : which air contributes to the briskness of this
and other mineral waters.

From minerals much air may be extracted. Half an
irtch of Newcastle coal yielded 1 80 inches of air, which
weighed near one third of the coal.

Yet a good part of the air extracted from these
bodies in some days gradually lost its elasticity, because
the acid, sulphureous fumes, raised with the air, re-
sorbed and fixed the elastic particles* But when a
means was found to prevent this, it lost only a seven-
teenth or eighteenth part ; and that chiefly in the first
twenty-four hours ; the rest was permanently elastic.

There is another way of producing air, which seems
to be jnore natural, namely, by fermentation^ A cubic
inch of * oil of vitriol, with half an inch of sal ammoniac
generated six cubic inches of air ; six inches of powdered
oyster-shells, and an equal quantity of white-wine vinegar,
generated twenty nine inches.

* Mr. Gsqffry shews that the mixture of any vitriolic salfs with
iuflammuble substances will yield common brimstone; particu-
larly or' oil of vitriol with oil of turpentine. Brimstone there-
fore is nothing but vitriolic salt united with some combustible



That much air- is Incorporated into the substance of'
vegetables, appears from the follow ing experiments.

Forty-two inches of ale,, 1 from the tun, generated, in
three months, 636" cubic inches of air: twelve inches of*
rnalaga raisins, in six weeks, generated 431 inches:
twenty-six inches of apples, . in thirteen days, generated
f)6S inches of air. f i hey then, in three or four days, re-
sorbed about twelve inches*., and afterwards neither-'
generated nor rcsorbed.

That the air arising from distilled or fermenting
bodies is true air appears from hence, that it continues
in the same expanded state for weeks, or months, which
expanded vapours w.jH not do. And that it is elastic-
appears by its dilating and contracting with heat and-
cold as common air does.

Air then makes a very considerable part of the sub-
stance of vegetables as well as animals. And beside
these particles of air, which strongly adhere- to, and are
wrought into their substance, there is in them a large
quantity which is upon the wing, and in a very active
state.

To shew how much air is contained in white paper,
take as many slips of it as weigh a hundred grains.*-
Euro these warily by the flame of a candle, and then
weigh the ashes : you will find the hundred grains re-
duced to six; so ninety-four grains out of one hundred
are undeniably transformed into* sir. They could not
be. annihilated; and they could not rise and flyaway
without a repelling force to carry them. off. Thus the
candle itself is by degrees transformed from heavy, pal-
pable wax, into a light, impalpable body- of air. But
observe, all bodies which thus become air, pass through
the intermediate state of flame ; so that, properly speak-
ing, the same body was one moment paper, the second
zuameiit jire, and the third, air. How different states .
for the same sort of matter to subsist in, in- so*short a.-/,
time !

The air-pump shews how much air is even in water*
Place a tail glass of water in the receiver; turu the*



143

- winch anci you see bubbles of air through the body of

-the water. First, they are thick, but small; then they

, grow. large, and rise to the top of the water. And as

long as the pump works, so long the air rises, but more

aloirly, and in. larger bubbles* In wine the air-bubbles

.-rush violently to the top and burst; nay, and the liquor

perfectly boils like water on the fire. Yea, and hot

water may be made to boil by -the air-pump as v?ell ;is

by lire. Hence it appears, that boiling is nothing but

the motion produced from the -.-/expansion of the air,

whether by tire, or by the warmth and pump conjointly,

By another experiment it appears, that any piece of

-wood is pervious to tiie air, and that its air-vessels run

through the whole length or substance uf the tree.-

Nay, quicksilver may be made to pass through a piece

of wood, and descend in the form of a shower of rain.

By the air-pump we likewise measure the weight, and

.find that a pint of it weighs 8 grains. Consequently a

: ;;v! I on weighs a little more than a drachm: therefore a

bushel weighs an ounce and huSf^a drachm.

Another experiment proves what one would not sus-
pect. Bodies moving in a fluid meet so much the more
resistance, as tlieir bulk is larger in equal weight. So a
cork, of equal weight with a guinea, meets with so much
the moro resistance from the air. But in an exhausted
receiver, the largest bulk of cork, .which was before the
most resisted, now proves the heavier body, and accord-
ingly falls more swiftly than the gold.

Again. Strike a flint against the steel invacuo, and
it will occasion no sparks, So necessary is air to the
'very appearance of fire.

Air is generated likewise from minerals by fermen- -
tation. By other fermenting mixtures it is absorbed-
.again, and by others generated and absorbed alternately.
A quarter of an inch of jilings of iron; and an inch of
compound aquafortis, in four days absorbed 27 inches
of air. When hot water was poured upon it, it gt?ne-
r.aied three or four inches, which after some da\s it ab-
sorbed again. A quarter of an inch of iron filings, with
an inch of powdered brimstone, absorbed nineteen inches



U4

in two days. Powdered brimstone mixed with New-
castle coal,* neither generated nor absorbed.

An inch of chalk, and as much oil of vitriol, in three
days generated 31 inches of air. Part of this it after-
wards resorbed. Two inches of lime, and as much sal
ammoniac, absorbed 115 inches. Tiie fumes of this
are therefore very suffocating. All burning and flaming
bodies absorb much air. And whereas the air which
some substances absorb is afterwards remitted, that
which is absorbed by burning brimstone by the flame of
a candle, or by human respiration, does not recover its
elasticity.

The elasticity of the air in the vesicles of the lungs is
continually decreasing through the vapour it is there
loaded with, so that there needs fresh air continually,
otherwise those vesicles will soon fall flat, whereby the
motion of the blood through the lungs being stopr, in-
stant death ensues. And this seems to be exactly the
case of most of those who are killed by lightning, which
so totally destroys the elastic air in the lungs, that they
instantly fail flat.

31. Many have imagined that the animal fluids are
furnished with air by the lungs only. But undoubtedly
they are also supplied therewith by way of the chyli-
ferous canals, and that in no small quantity : for*the
air, like all other animal fluids, requires to be perpetually
renewed; accordingly old particles fly oflf every moment,
and new ones succeed in their place.

It may fee demonstrated, that urine contains much
air. Doubtless so does the perspirable matter, which
being the lightest of all animal- fluids, is the chief
vehicle of the effete and useless air.

And that candles soon go out, if they are confined in
a small quantity of air, seems not to be so much owing
to their having rendered the air effete, by consuming its
vivifying spirit, as to its destroying the elasticity thereof
by its acid, fuliginous vapours.

But nothing destroys the elasticity of air like brim-
stone, whether burning or in fermenting mixtures. And



145

as the attractive power of bodies is found to be more or
less, as they have more or fewer sulphureous particles,
so we may reasonably ascribe the fixing the elastic par-
ticles of air to the strong attraction of the sulphureous
particles, with which Sir Isaac Newton supposes all
bodies to abound more or less.

The vavious mixtures in the stomach sometimes gene-
rate, sometimes absorb air. In a good digestion the
generating power exceeds the absorbing power but a
little. When it exceeds it much, we are troubled, more
or less, with distending flatus's.

We have seen how much air may be extracted from
animal and vegetable bodies, into whose substances it
was before intimately and firmly incorporated, and con-
sequently great quantities of air must be continually Ex-
pended in their production. Part of this, we see, may
resume its elastic state when their texture is dissolved ;
but part probably never regains its elasticity, at least,
not in many centuries. However, we may see what im-
mense treasures of this important element, the wise
author of nature has abundantly provided, the constant
waste of it being abundantly supplied by heat or fer-
mentation from innumerable dense bodies.

If all the parts of nature were endued with a strongly
attracting power only, whole nature would immediately
become one unactive, coherent lump. It was therefore
absolutely necessary there should be every where inter-
mixed, a due proportion of strongly elastic particles.
And since abundance of these are continually reduced
from an elastic to a fixed state, it was also necessary
that these particles should be endued with a property
of resuming their elasticity, whenever they were disen-
gaged from that mass in which they were fixed. And
hereby this beautiful frame of things is maintained in a
continual round, of the production and dissolution of
animal and vegetable bodies.

The air is very instrumental in the production and
growth of animals and vegetables, in its ela-stic state, by
invigorating their juices; and in its fixed state, bv
greatly contributing to the union and firm connection of



146

their -constituent parts. It is also a very powerful agent
-in the dissolution of the tame bodies.

32. That fixed air is a cementing principle appears
'(to omit 'Others) from that well known experiment.
Quick lime dissolves flesh by extracting and imbibing,
the fixed air which it contained. But while the flesh
falls in pieces from the loss of the .principle, the lime
grows solid by having it restored.

That it contributes also to the dissolution of bodies
appears hence. During the progress of putrefaction, a
volatile matter flies .continual fy from the putrefying sub-
stance. And this is no other .than air which is now ex-
tricated and thrown oft from a fixed and uneiastic state,
but immediately returns to it again on meeting with a
proper recipient.

The preserving lod'ws from putrefaction depends
almost in every instance on restraining the flight of the
fixed air. For as this cements their constituent parts,
so putrefaction, which is the disunion of them, cannot
take place while this remains.

And this air both corrects and prevents putrid acri-
3nony in the animal -fluid. Hence any food which does
not contain a due proportion of it, is found to promote
putrefaction : as do all damaged vegetables, which
being ineapable of fermentation, are incapable of pro-
<!ucing the due quantity of air.

BuO pure air is no where to be found. That which
surrounds us is the most heterogeneous body in nature*
It is no other than an universal diaos, a coiluvies of all
lands of bodies. No bodies can withstand the force of
lire. And whatever fire can volatilize is found in the air.
Hence for instance, the whole fossil kingdom must be
.found therein : for all that tribe is convertible into fume.
Gold, the most fixed of all, adheres to sulphur in mines,
and is raised along with it. All the parts of the animal
kingdom must likewise be in the air. For besides the
copious effluvia they emit by perspiration (whereby an
animal in the course of its duration, impregnates the air
with many times the quantity of its own body), any dead

3



117

animal, when exposed to the air, is in a certain time
carried wholly oft*. And we know that all vegetables by
putrefaction become volatile, and so evaporate into air.

Air, 2. Volatilizes fixed bodies. Thus sea salt being
calcined and fused, then exposed to the air to liquify;
when liquified, set to dry again ; then fused again, and
the operation thus repeated ; will by degrees be almost
wholly evaporated, nothing remaining but a little earth.
Air, 3. Fixes volatile bodies. Thus though aqua fortis,
or spirit of nitre, readily evaporates by the fire ; yet if
the air near be impregnated with spirit of urine, the vo-
latile spirit is fixed, and falls down in a liquid form.

But the air's being open or enclosed is of consequence
in chymical operations. So, to make sulphur inflamma-
ble, a free air is required : in a close vessel it will not
kindle. And thus all animals and vegetables can only
be calcined in open air. In close vessels they never
become any other than black coals.

By the air-pump the air is in a great measure drawn
out of a vessel called the receiver. And hence we learn
how much all vital, nutritive, and alterative powers, de-
pend upon the air. A candle in the exhausted receiver
usually goes out in a minute. A kindled charcoal is to-
tally extinguished in about five minutes. Red hot iron
is not affected thereby : only it will not light sulphur or
gunpowder, but melt it. Loadstones act, as well as in
the open air. Smoke sinks in a darkish body to the
bottom, leaving the upper part clear and transparent.
The syphon does not run therein : but attrition produces
beat, as in the open air. "If some grains of a heap of
gunpowder be kindled by a burning-glass, they will not
tire the contiguous grains. G low-worms lose their light as
the air is exhausted ; but recover it not on its re-admission.
Vipers and frogs seem dead in less than two hours, but
recover in the open air. Snails live ten hours : efts two
or three days ; leeches five or six.

The atmosphere is a body of air and vapours, which
surrounds the globe to the height of at least sixty miles,
gravitates towards its centre, and is carried along with

in all its motions. This continually presses on our

VOL, in. H



foodies, with awei'ght equal to a pillar of air, whose base
is equal to the surface of our bodies. Now a pillar of
air of the height of the atmosphere, is equal to a pillar
of water thirty-two feet high. Every foot square there-
fore of the surface of our bodies is pressed on by a
weight of air, equal to 35 cubic feet of water : and a
cubic foot of water weighing ?6 pound, (Troy weight;,
consequently every foot square of the surface of our
bodies sustain a pillar of air, equal to 2,S()0 pounds. If
then (he surface of a man's body contains fifteen square
feet, he sustains a weight equal to 3 t 9,9pO pounds. This
is the case, when the air is heaviest. But the difference
between the greatest and the least pressure of air upon
our bodies is equal to 3982 pounds.

Hence it is so far from being a wonder, we should
sometimes suffer in our health, by a change of weather,
that it is the greatest wonder we should not always suffer.
For when we consider our bodies are at sometimes prest
upon by near two tons weight more than at others, it is
surprising that every change does not break our whole
frame to pieces.

In truth the vessels of our bodies being so much strait-
ened by an increased pressure, would stagnate the blood
to the very heart, had not the Author of nature \visely
contrived, that when the resistance to its circulation is
greatest, the force by which the heat contracts should be
so too. For upon an increase of the weight of the air,
the lungs are more strongly expanded, and the blood by
being more intimately broken, made fitter for finer secre-
tions; the nervous in particular, by which the heart is
more strongly contracted. On the other hand, when
the weight tff the ambient air is ever so little abated, the
air contained within the blood, unfolds its springs, and
forces the blood to take up a largtr space than it did
before.

The reason we are not sensible of this pressure, is well
explained by Borelli : sand, perfectly rammed into a hard
vessel, cannot be penetrated, even by a wedge. And
water m a bladder, compressed on all sides, cannot give
nay in any part. In like manner, within the skin of an

4



animal, are contained various parts : some hard, as bone? t
some soft, as muscles ; and some fluid, as blood. Now
it is not possible that bones should be broke or displaced
in the body, unless the pressure lay heavier on one part
than another. If the pressure be so divided, that it
be equal all round, upward, downward, sideways, and
no part of the skin to be exempt therefrom, it is plain,
no fracture or luxation can follow.

The same may be observed of the muscles and nerves*
which though soft, yet being composed of solid fibres-,
'do mutually sustain each other, and resist the common
weight. The same holds of the blood and other hu-
mours. As water is not capable of condensation, so
these liquids, while contained in these vessels, cannot be
forced out of them by an universal compression. Add
to this, that the air itself which is contained- in every
part or the body, is such a balance to the external air,
that no hurt can ensue from its pressure.

33. Oil of vitriol, when exposed to the air, conti-
nually increases in weight. Let a phial of this stand
unstopped, and it will be constantly running over. Per-
haps the cause of this odd phenomenon is, tlie moisture
contained in the air, which this liquor^ a potential fire,
imbibes as greedily, as actual fire does nitre.

34. At the height of forty-one miles, tlte air is so ra-
refied, as to take up three thousand times the space it
does here. At fifty-three miles high, it would be ex- ,
panded thirty thousand times as much as it is here.

At that distance, (as was observed) it is expanded into
three thousand times the space it occupies here. Arid
we have seen- it condensed into the sixteenth part of the
same space. It seems then, that the air is capable of
being condensed into the hundred and eighty thousandth
part of the space it would take up when free from pres-
sure. But what texture must it be of, to make it capa-
ble of this immense .expansion and contraction? How
imperfectly is this accounted for, by comparing it to
wool, cotton,, and the like elastic bodies.



150

35. But there is art amazing difference between the
fixed and the common air, with regard to their effects
upon animal bodies. The fixed air, even when set free,
and in a state of perfect elasticity, whether it be during
the first stage of fermentation by fire, by effervescence,
or by putrefaction ; if it be received into the lungs of
any animal, causes instant death. But the same air,
when received into the stomach, whether thrown off* by
effervescent mixtures in medicine, or extricated from the
food by natural fermentation ; in the first instance often
operates like a charm, in restraining vomitings $ and in
the second is absolutely needful, for the support of life
and health.

With regard to the common air, on the contrary, no
animal can live long without taking large quantities of
it into the lungs. Yet if a small portion of it be forced
into the blood-vessels of any animal, death presently
ensues.

So that these two species of air have quite different
provinces, with respect to animal life. The first, com-
mon air, must mix wholly with the blood. The second
only communicates some subtle matter to it : probably
electric fire, which we know is connected with every par-
ticle of common air.



151



CHAP. III.

Of Meteors.

l. Of Vapours, Mists, ani 7. Of Thunder and Lightning

Clouds. 8. Of Damps.

3. Of Dew and Rain, 9. Of Ignes Fatui

3. Of Snow and Hail. 10. Of Electricity.

4. Of the Rainbow. . 11. Of Ether of Plants.

5. Of the Halo. 12. Of Wind.

6. Of mock Suns and Moons. 13. Reflections.



1. \\ HATSOEVER is carried aloft into the air, and
suspended there, is termed a meteor. These are either
watry, fiery, or airy. The watry, are mists, clouds,
rain, snow, hail. Watry particles which are rarified so
as to float in the air, are then termed vapours. If these
are visible and hang near the earth, we call them mists ;
if they are higher in the air, cjouds. Some of these are
so thin, as to transmit the rays of the sun, others so
dense as to intercept them;

The manner wherin the vapours that constitute clouds
and .rain are raised, seems to be this. Fire being the
lightest of all bodies, easily breaks loose from them ;
and in its passage carries along with it particles or little
cases of water. These being lighter than the air, are
buoyed up, and swim therein ; till striking against one ano-
ther, or thickened by cold, they are reduced into clouds
and drops.

To illustrate this, we may observe in water over the
fire, 1. That the evaporations are proportioned to the
heat. A small heat throws off few vapours, scarce visi-
ble : a greater heat carries off larger and more numer-
H 3



152

QMS vesicles of water, which we call a steam. Violent
heats lifts up great quantities of water, which the air can-
not buoy up : and this we call boiling. 2. If the.se va-
pours be intercepted in their ascent, by any dense body,,
especially if it be cold ; they are thereby reduced into
drop?, Uke those of rain. 3. In frosty weather the
vapours rise but a little above the water, and there hang
or glide on. If the weather be cold ; after a little as-
ceut, they fail again into the water. But in a warm still
air, they ascend swiftly and largely, and mount up, till
they are out of sight.

To explain this a little farther, it may he observed,
that the parts of water being so small and moveable, are
easily separated from one another. And when they are
so divided into small parcels, as to become about eight
hundred times lighter than common water, they are as
light as the air, and will by every successive degree of
separation, rise in the air in proportion to their lightness,
the heavier air forcing the rarified fluid to ascend into
the atmosphere, till it finds a place in equilibrium among
bodies of equal lightness to itself. This separation, or
Comminution (ir 1 may so call it), of Water into small par-
cels, may be performed either by collision against harder
and more compact bodies, or by heat. The first we
often see performed at the bottom of cascades, where
the water that falls but a few fathoms, shnll rise in a
mist from the bottom where it is broke; and there are
instances of clouds rising from the fail of waters, whieii
may be seen five miles of. Collision will therefore ex-
cite vapours : but what is more constantly producing
this effect in every part of the universe, is heat : whether
from the sun, which is always busy this way, or from ar-
tificial ignition, or that generally invisible elemental fire,
which is distributed through all matter, It is not neces-
sary for us to consider in this case, any other than the
divisibility of water, and the insinuating and dispersive
qualities of fire. Fire we see separates more or less the
parts of all bodies, whether fluid or solid, and makes
them rise in. the air; and it does no more to water ; it



153

separates it into such small portions, that the air is more
ponderous than the steam, and of consequence remains
nearer the earth by its superior gravitation.

2. The dew which usually falls inEnglamt in a year,
amounts to something more than three inches and a
quarter depth. The evaporation of a winter's day is
nearly the same as that of a summer's day. For the'
earth being moister in winter, that excess of moisture
answers to the excess of heat in summer.

Within the tropics they have no rain for many months
together. But the dews are far greater than with us.
Yet the moisture evaporated in a summer's day, far ex-
ceeds that which falls in the night. Hence the dews
there cannot be of any benefit to the roots of the trees,


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Online LibraryJohn WesleyA survey of the wisdom of God in the creation; or, A compendium of natural philosophy .. (Volume 3) → online text (page 13 of 24)