3. I must admit that I have bestowed no little trouble upon this

matter in order to obtain a clear conception of it. One may reasonably

be amazed at the ideas and conjectures which authors have recorded

on the subject, especially when they give a decision respecting the

phenomenon of fire; and this very matter was of the greatest importance

to me. I perceived the necessity of a knowledge of fire, because

without this it is not possible to make any experiment; and without

fire and heat it is not possible to make use of the action of any

solvent. I began accordingly to put aside all explanations of fire; I

undertook a multitude of experiments in order to fathom this beautiful

phenomenon as fully as possible. I soon found, however, that one could

not form any true judgment regarding the phenomena which fire presents,

without a knowledge of the air. I saw, after carrying out a series of

experiments, that air really enters into the mixture of fire, and with

it forms a constituent of flame and of sparks. I learned accordingly

that a treatise like this, on fire, could not be drawn up with proper

completeness without taking the air also into consideration.

4. Air is that fluid invisible substance which we continually breathe,

which surrounds the whole surface of the earth, is very elastic, and

possesses weight. It is always filled with an astonishing quantity

of all kinds of exhalations, which are so finely subdivided in it

that they are scarcely visible even in the sun’s rays. Water vapours

always have the preponderance amongst these foreign particles. The

air, however, is also mixed with another elastic substance resembling

air, which differs from it in numerous properties, and is, with good

reason, called aerial acid by Professor Bergman. It owes its presence

to organised bodies, destroyed by putrefaction or combustion.

5. Nothing has given philosophers more trouble for some years than just

this delicate acid or so-called fixed air. Indeed it is not surprising

that the conclusions which one draws from the properties of this

elastic acid are not favourable to all who are prejudiced by previously

conceived opinions. These defenders of the Paracelsian doctrine believe

that the air is in itself unalterable; and, with Hales, that it really

unites with substances thereby losing its elasticity; but that it

regains its original nature as soon as it is driven out of these by

fire or fermentation. But since they see that the air so produced is

endowed with properties quite different from common air, they conclude,

without experimental proofs, that this air has united with foreign

materials, and that it must be purified from these admixed foreign

particles by agitation and filtration with various liquids. I believe

that there would be no hesitation in accepting this opinion, if one

could only demonstrate clearly by experiments that a given quantity

of air is capable of being completely converted into fixed or other

kind of air by the admixture of foreign materials; but since this has

not been done, I hope I do not err if I assume as many kinds of air as

experiment reveals to me. For when I have collected an elastic fluid,

and observe concerning it that its expansive power is increased by heat

and diminished by cold, while it still uniformly retains its elastic

fluidity, but also discover in it properties and behavior different

from those of common air, then I consider myself justified in believing

that this is a peculiar kind of air. I say that air thus collected must

retain its elasticity even in the greatest cold, because otherwise an

innumerable multitude of varieties of air would have to be assumed,

since it is very probable that all substances can be converted by

excessive heat into a vapour resembling air.

6. Substances which are subjected to putrefaction or to destruction by

means of fire diminish, and at the same time consume, a part of the

air; sometimes it happens that they perceptibly increase the bulk of

the air, and sometimes finally that they neither increase nor diminish

a given quantity of air--phenomena which are certainly remarkable.

Conjectures can here determine nothing with certainty, at least they

can only bring small satisfaction to a chemical philosopher, who must

have his proofs in his hands. Who does not see the necessity of making

experiments in this case, in order to obtain light concerning this

secret of nature?

7. General properties of ordinary air.

(1.) Fire must burn for a certain time in a given quantity of air.

(2.) If, so far as can be seen, this fire does not produce during

combustion any fluid resembling air, then, after the fire has gone

out of itself, the quantity of air must be diminished between a third

and a fourth part. (3.) It must not unite with common water. (4.) All

kinds of animals must live for a certain time in a confined quantity of

air. (5.) Seeds, as for example peas, in a given quantity of similarly

confined air, must strike roots and attain a certain height with the

aid of some water and of a moderate heat.

Consequently, when I have a fluid resembling air in its external

appearance, and find that it has not the properties mentioned, even

when only one of them is wanting, I feel convinced that it is not

ordinary air.

8. Air must be composed of elastic fluids of two kinds.

First Experiment.--I dissolved one ounce of alkaline liver of sulphur

in eight ounces of water; I poured four ounces of this solution into an

empty bottle capable of holding 24 ounces of water, and closed it most

securely with a cork; I then inverted the bottle and placed the neck

in a small vessel with water; in this position I allowed it to stand

for fourteen days. During this time the solution had lost a part of its

red colour and had also deposited some sulphur: afterwards I took the

bottle and held it in the same position in a larger vessel with water,

so that the mouth was under and the bottom above the water-level, and

withdrew the cork under the water; immediately water rose with violence

into the bottle. I closed the bottle again, removed it from the water,

and weighed the fluid which it contained. There were 10 ounces. After

substracting from this the four ounces of solution of sulphur there

remain six ounces, consequently it is apparent from this experiment

that of 20 parts of air six parts have been lost in 14 days.

9. Second Experiment.--(a) I repeated the preceding experiment with the

same quantity of liver of sulphur, but with this difference that I only

allowed the bottle to stand a week tightly closed. I then found that of

20 parts of air only 4 had been lost. (b) On another occasion I allowed

the very same bottle to stand four months; the solution still possessed

a somewhat dark yellow colour. But no more air had been lost than in

the first experiment, that is to say six parts.

10. Third Experiment.--I mixed two ounces of caustic ley, which

was prepared from alkali of tartar and unslaked lime and did not

precipitate lime-water, with half an ounce of the preceding solution of

sulphur, which likewise did not precipitate lime-water. This mixture

had a yellow colour. I poured it into the same bottle, and after this

had stood fourteen days, well closed, I found the mixture entirely

without colour and also without precipitate. I was enabled to conclude

that the air in this bottle had likewise diminished, from the fact that

air rushed into the bottle with a hissing sound after I had made a

small hole in the cork.

11. Fourth Experiment.--(a) I took four ounces of a solution of

sulphur in lime-water; I poured this solution into a bottle and closed

it tightly. After 14 days the yellow colour had disappeared, and of 20

parts of air 4 parts had been lost. The solution contained no sulphur,

but had allowed a precipitate to fall which was chiefly gypsum. (b.)

Volatile liver of sulphur likewise diminishes the bulk of air. (c.)

Sulphur, however, and volatile spirit of sulphur, undergo no alteration

in it.

12. Fifth Experiment.--I hung up over burning sulphur, linen rags which

were dipped in a solution of alkali of tartar. After the alkali was

saturated with the volatile acid, I placed the rags in a flask, and

closed the mouth most carefully with a wet bladder. After three weeks

had elapsed I found the bladder strongly pressed down; I inverted

the flask, held its mouth in water and made a hole in the bladder;

thereupon water rose with violence into the flask and filled the fourth

part.

13. Sixth Experiment.--I collected in the bladder the nitrous acid

which arises on the dissolution of the metals in nitrous acid, and

after I had tied the bladder tightly I laid it in a flask and secured

the mouth very carefully with a wet bladder. The nitrous air gradually

lost its elasticity, the bladder collapsed, and became yellow as if

corroded by _aqua fortis_. After 14 days I made a hole in the

bladder tied over the flask, having previously held it, inverted, under

water; the water rose rapidly into the flask, and it remained only

two-thirds empty.

14. Seventh Experiment.--(a.) I immersed the mouth of a flask in a

vessel with oil of turpentine. The oil rose in the flask a few lines

every day. After the lapse of 14 days the fourth part of the flask

was filled with it. I allowed it to stand for three weeks longer, but

the oil did not rise higher. All those oils which dry in the air, and

become converted into resinous substances, possess this property. Oil

of turpentine, however, and linseed oil rise up sooner if the flask is

previously rinsed out with a concentrated sharp ley. (b.) I poured two

ounces of colourless and transparent animal oil of Dippel into a bottle

and closed it very tightly; after the expiration of two months the oil

was thick and black. I then held the bottle, inverted, under water and

drew out the cork; the bottle immediately became one-fourth filled with

water.

15. Eighth Experiment.--(a.) I dissolved two ounces of vitriol of iron

in thirty-two ounces of water, and precipitated this solution with

a caustic ley. After the precipitate had settled, I poured away the

clear fluid and put the dark green precipitate of iron so obtained,

together with the remaining water, into the before-mentioned bottle (§

8), and closed it tightly. After 14 days (during which time I shook the

bottle frequently) this green calx of iron had acquired the colour of

crocus of iron, and of 40 parts of air 12 had been lost. (b.) When iron

filings are moistened with some water and preserved for a few weeks

in a well closed bottle, a portion of the air is likewise lost. (c.)

The solution of iron in vinegar has the same effect upon air. In this

case the vinegar permits the dissolved iron to fall out in the form of

a yellow crocus, and becomes completely deprived of this metal. (d.)

The solution of copper prepared in closed vessels with spirit of salt

likewise diminishes air. In none of the foregoing kinds of air can

either a candle burn or the smallest spark glow.

16. It is seen from these experiments that phlogiston, the simple

inflammable principle, is present in each of them. It is known that the

air strongly attracts to itself the inflammable part of substances and

deprives them of it: not only this may be seen from the experiments

cited, but it is at the same time evident that on the transference of

the inflammable substance to the air a considerable part of the air

is lost. But that inflammable substance alone is the cause of this

action, is plain from this, that, according to the tenth paragraph,

not the least trace of sulphur remains over, since, according to my

experiments this colourless ley contains only some vitriolated tartar.

The eleventh paragraph likewise shows this. But since sulphur alone,

and also the volatile spirit of sulphur, have no effect upon the air (§

11. c), it is clear that the decomposition of liver of sulphur takes

place according to the laws of double affinity--that is to say, that

the alkalies and lime attract the vitriolic acid, and the air attracts

the phlogiston.

It may also be seen from the above experiments, that a given quantity

of air can only unite with, and at the same time saturate, a certain

quantity of the inflammable substance: this is evident from the ninth

paragraph, letter b. But whether the phlogiston which was lost by the

substances was still present in the air left behind in the bottle,

or whether the air which was lost had united and fixed itself with

the materials such as liver of sulphur, oils, &c., are questions of

importance.

From the first view, it would necessarily follow that the inflammable

substance possessed the property of depriving the air of part of its

elasticity, and that in consequence of this it becomes more closely

compressed by the external air. In order now to help myself out of

these uncertainties, I formed the opinion that any such air must

be specifically heavier than ordinary air, both on account of its

containing phlogiston and also of its greater condensation. But how

perplexed was I when I saw that a very thin flask which was filled with

this air, and most accurately weighed, not only did not counterpoise

an equal quantity of ordinary air, but was even somewhat lighter. I

then thought that the latter view might be admissible; but in that case

it would necessarily follow also that the lost air could be separated

again from the materials employed. None of the experiments cited seemed

to me capable of showing this more clearly than that according to the

tenth paragraph, because this residuum, as already mentioned, consists

of vitriolated tartar and alkali. In order therefore to see whether the

lost air had been converted into fixed air, I tried whether the latter

shewed itself when some of the caustic ley was poured into lime-water;

but in vain--no precipitation took place. Indeed, I tried in several

ways to obtain the lost air from this alkaline mixture, but as the

results were similar to the foregoing, in order to avoid prolixity I

shall not cite these experiments. Thus much I see from the experiments

mentioned, that the air consists of two fluids, differing from each

other, the one of which does not manifest in the least the property

of attracting phlogiston, while the other, which composes between the

third and the fourth part of the whole mass of the air, is peculiarly

disposed to such attraction. But where this latter kind of air has gone

to after it has united with the inflammable substance, is a question

which must be decided by further experiments, and not by conjectures.

FOOTNOTES:

[Footnote 18: Translated from _Treatise on Air and Fire_ (1777).]

XVII

ANTOINE LAURENT LAVOISIER

1743-1794

_Antoine Laurent Lavoisier was born in Paris, August 26, 1743.

After an early life spent in diligent study, in 1766 he was awarded

a prize for his essay on the best method of lighting Paris. His

attention having been called to the English experiments on gases

made by Priestley and Cavendish, he attacked the current phlogiston

conception of combustion and stated that Priestley’s “dephlogisticated

air” was the universal acidifying gas, and gave it the name of

“oxygen.” Systematizing chemistry and renaming the elements and their

compounds, he came to believe that chemical reactions had the certainty

of mathematical equations. From this he derived the idea of the

persistence of matter, regardless of changes, now established as one of

the basic concepts of modern science. During the French Revolution a

charge was brought against him and he was sent to the guillotine on May

8, 1794._

THE NATURE OF COMBUSTION[19]

I venture to submit to the Academy to-day a new theory of combustion,

or rather, to speak with that reserve to whose law I submit myself,

an hypothesis, by the aid of which all the phenomena of combustion,

calcination, and even to some extent those accompanying the respiration

of animals are explained in a very satisfactory manner. I had already

laid the foundations of this hypothesis p. 279-280 of vol. I. of my

_Opuscules physiques et chimiques_; but I admit that trusting

little to my own knowledge, I did not then dare to put forward an

opinion which might seem singular, and which was directly opposed to

the theory of Stahl and of many celebrated men who have followed him.

Though perhaps some of the reasons which then checked me still remain

to-day, nevertheless, the facts which have multiplied since that

time, and which seem to me favorable to my views, have confirmed

me in my opinion: though not, perhaps, any stronger, I have become

more confident, and I think I have sufficient proofs, or at least

probabilities, so that even those who may not be of my opinion cannot

blame me for having written.

In general in the combustion of bodies four constant phenomena are

observable, which seem to be laws from which nature never departs.

Though these phenomena may be found implicitly stated in other memoirs,

yet I cannot dispense with recalling them here in a few words.

FIRST PHENOMENON

All combustion sets free matter either of fire or light.

SECOND PHENOMENON

Bodies can burn only in a very small number of kinds of gases (airs),

or rather there can be combustion only in one kind of air, that which

Mr. Priestley has named dephlogisticated air, and which I should call

pure air. Not only will the bodies which we call combustibles not burn

in a vacuum or in any other kind of air, they are, on the contrary,

extinguished there as promptly as if they had been plunged into water

or any other liquid.

THIRD PHENOMENON

In all combustion there is destruction or decomposition of the pure

air in which the combustion takes place, and the body burned increases

in weight exactly in proportion to the quantity of air destroyed or

decomposed.

FOURTH PHENOMENON

In all combustion the body burned changes to an acid by the addition

of the substance which has increased its weight: thus, for example,

if sulphur is burned under a receiver the product of the combustion is

vitriolic acid; if phosphorus be burned the product is phosphoric acid;

if a carboniferous substance, the product is fixed air, otherwise known

as acid of lime (carbonic acid, etc.).

(Note: I would remark in passing that the number of acids is infinitely

greater than has been supposed.)

The calcination of metals is subject to exactly the same laws, and it

is with very great reason that Mr. Macquer has treated it as a slow

combustion; thus, 1°, in all metallic combustion there is a liberating

of fire matter (_matière du feu_); 2°, veritable calcination can

take place only in pure air; 3°, there is a combination of the air with

the substance calcined, but with this difference, that in place of

forming an acid with it there results from it a particular combination

known as metallic calx.

This is not the place to point out the analogy which exists between the

respiration of animals, combustion and calcination; I shall return to

that in the sequel to this memoir.

These different phenomena of the calcination of metals and of

combustion are explained in a very happy manner by Stahl’s hypothesis;

but it is necessary with him to suppose the existence of fire matter

(_matière du feu_) or of fixed phlogiston in the metals, in

sulphur and in all bodies which he regards as combustibles; yet if the

partisans of Stahl’s doctrine are asked to prove the existence of fire

matter in combustible bodies, they fall necessarily into a vicious

circle and are obliged to reply that combustible bodies contain fire

matter because they burn, and that they burn because they contain fire

matter. It is easy to see that in the last analysis this is explaining

combustion by combustion.

The existence of fire matter, or phlogiston, in metals, in sulphur,

etc., is then really only an hypothesis, a supposition which, once

admitted, explains, it is true, some of the phenomena of calcination

and combustion; but if I show that these very phenomena may be

explained in quite as natural a way by the opposite hypothesis, that

is to say, without supposing the existence of either fire matter or

phlogiston in the substances called combustible, Stahl’s system will be

shaken to its foundations.

No doubt you will not fail to ask me first what I understand by fire

matter. I reply with Franklin, Boerhaave and some of the philosophers

of old, that the matter of fire or of light is a very subtle, very

elastic fluid, which surrounds every part of the planet we live

on, which penetrates with more or less ease the substances which

compose that, and which tends, when it is free, to come to a state of

equilibrium in all.

I will add, borrowing the chemical phraseology, that this fluid is the

solvent of a large number of substances; that it combines with them

in the same way that water does with salt, and the acids with metals,

and that the bodies thus combined and dissolved by the igneous fluid

lose in part the properties which they had before the combination and

acquire new ones which bring them nearer (make them more like) the fire

matter.

It is thus, as I have shown in a memoir deposited with the secretary

of this Academy, that every aeriform fluid, every kind of air, is a

resultant of the combination of some substance, solid or fluid, with

the matter of fire or of light; and it is to this combination that

aeriform fluids owe their elasticity, their specific volatility, their

rarity, and all the other properties which ally (_rapprochent_)

them to the igneous fluid.

Pure air, according to this, what Mr. Priestley calls dephlogisticated

air, is an igneous compound into which the matter of fire or of light

enters as solvent, and into which some other substance enters as a

base; but if, in any solution whatever, a substance is presented to

the base with which that has greater affinity, it unites with this

instantly and the solvent which it leaves is set free.

The same thing happens with the air in combustion; the substance

which burns steals away the base; then the fire matter which served

as its solvent becomes free, regains its rights and escapes with the

characteristics by which we know it; that is to say, with flame, heat

and light.

To elucidate whatever may seem obscure in this theory let us apply it

to some examples: when a metal is calcined in pure air, the base of the

air, which has less affinity for its own solvent than for the metal,

unites with the latter as it melts and converts it into metallic calx.

This combination of the base of the air with the metal is proved 1st,

by the increase in weight which the latter undergoes in calcination;

2nd, by the almost total using up of the air under the receiving bell.

But, if the base of the air was held in solution by the fire matter,

in proportion as this base combined with the metal, the fire matter

should become free and produce, in freeing itself, flame and light. You

understand that the more speedy the calcination of the metal, that is

to say, the more fixation of the air takes place in a given time, the

more fire matter will be liberated, and, consequently, the more marked

and obvious the combustion will be.

I might apply this theory successively to all combustions, but as

I shall have frequent occasion to return to this subject, I will

content myself at this time with these general illustrations. So, to

resume, the air is composed, according to my idea, of fire matter as

a dissolvent combined with a substance which serves it as a base,

and which in some way neutralizes it; whenever a substance for which

it has a greater affinity is brought into contact with this base, it

leaves its solvent; then the fire-substance regains its rights, its

properties, and appears to our eyes with heat, flame and light.

Pure air, the dephlogisticated air of Mr. Priestley, is then, according

to this opinion, the real combustible body, and perhaps the only one of

that nature, and it is seen that it is no longer necessary, in order

to explain the phenomena of combustion, to suppose that there exists

a large quantity of fire fixed in all the substances which we call

combustible, but that it is very probable, on the contrary, that very

little of it exists in metals, in sulphur, phosphorus, and in most of

the very solid, heavy and compact bodies, and, perhaps even that there

exists in these substances only free fire matter, in virtue of the

property which this matter has of putting itself in equilibrium with

all surrounding bodies.

Another striking reflection which comes to the support of the preceding

ones, is that almost all substances may exist in three different

states: under a solid form, under a liquid form, that is to say

melted, or in the state of air or vapor. These three states depend

solely on the quantity, more or less, of fire matter with which these

substances are interpenetrated and with which they are combined.

Fluidity, vaporization, elasticity, are then properties characteristic

of the presence of fire and of a great abundance of fire; solidity,

compactness, on the contrary, are evidences of its absence. By so much

then as it is demonstrated that aeriform substances and air itself

contain a large quantity of fire in combination, by so much it is

probable that solid bodies contain little of it.

For the rest, I repeat, in attacking here the doctrine of Stahl, it was

not my purpose to substitute for it a rigorously demonstrated theory,

but only an hypothesis which seemed to me more probable, more in

conformity with the laws of nature, and one which appeared to involve

less forced explanations and fewer contradictions.

FOOTNOTES:

[Footnote 19: _On Combustion_, Vol. II, p. 225.]

XVIII

ALESSANDRO VOLTA

1745-1827

_Alessandro Volta, born at Como, Italy, February 18, 1745, became

teacher of physics at Como in 1774, and five years later accepted a

professorship at Pavia. Becoming interested in Galvani’s experiments

with electricity on the muscles of a frog, he applied them in his

attempts to confirm his own theory that the frog’s muscles were a

sensitive electrometer. In doing this he conceived the voltaic pile,

which produced the first constant electrical current--a discovery which

had immense effects in later studies in electricity. He died at Como,

March 5, 1827._

NEW GALVANIC INSTRUMENT[20]

ON THE ELECTRICITY EXCITED BY THE MERE CONTACT OF CONDUCTING SUBSTANCES

OF DIFFERENT KINDS

The chief of these results, and which comprehends nearly all the

others, is the construction of an apparatus which resembles in its

effects, viz. (such as giving shocks to the arms, &c.,) the Leyden

phial, and still better, electric batteries weakly charged; acting

continually, or whose charge, after each explosion, recharges itself

again; which in short becomes perpetual, from one infallible charge,

from one action or impulse on the electric fluid; but which besides

differs essentially from the other, by this continual action which

is proper to it, and because that instead of consisting, like the

ordinary phials and electric batteries, in one or more isolated plates,

or thin layers of those bodies deemed the only electrics, and armed

with conductors or bodies called non-electrics, this new apparatus is

formed only of a number of these last bodies, chosen even among the

best conductors, and so the farthest removed, according to the usual

opinion, from the electric principle. This astonishing apparatus is

nothing but an assemblage of a number of good conductors of a different

kind, arranged in a certain manner. Thus, 30, 40, 60, or more pieces

of copper, or better of silver, each applied to a piece of tin or

still better of zinc, and an equal number of layers of water, or of

some other liquid which may be a better conductor than simple water,

as salt water, lye, &c., or of bits of card or leather, &c., soaked

in such liquids. Of such layers interposed between each couple or

combination of two different metals, one such alternate series, and

always in the same order, of these three kinds of conductors, is all

that constitutes M. Volta’s new instrument; which imitates so well

the effects of the Leyden phial or electric batteries; not indeed

with the force and explosions of these, when highly charged; but only

equalling the effects of a battery charged to a very weak degree, of

a battery, however, having an immense capacity, but which besides

infinitely surpasses the virtue and the power of these same batteries;

as it has no need, like them, of being charged beforehand, by means

of a foreign electricity; and as it is capable of giving the usual

commotion as often as ever it is properly touched. This apparatus, as

it resembles more the natural electric organ of the torpedo, or of the

electric eel than the Leyden phial and the ordinary electric batteries,

M. Volta calls the artificial electric organ. For the construction of

this instrument, M. Volta provides some dozens of small round metal

plates of copper, or tin, or best of silver, about an inch in diameter,

like shillings or half-crowns, and an equal number of plates of tin,

or much better of zinc, of the same shape and size. These pieces he

places exactly one upon another, forming a column, pillar or pile. He

provides also as many round pieces of card, or leather, or such like

spongy matter, capable of imbibing and retaining much of the water, or

other liquid, when soaked in it. These soaked roullets or circles are

to be a little less in diameter than the small metal discs or plates,

that they may not jut out beyond them. All these discs are then placed

horizontally on a table, one over another continually alternating, in a

pile as high as will well support itself without tottering and falling

down: beginning with a plate of either of the metals, as for instance,

the silver, then upon that one of zinc, over which is to be put the

soaked card; then other three discs, over these in the same order, viz.

a silver, next a zinc, and then another moistened card, &c.

After having raised the pile to about 20 of these stages or triads of

plates, it will be already capable, not only of affecting Cavallo’s

electrometer, assisted by the condenser, so as to raise it 10 or 15°,

charging it by a simple touching, so as to cause it to give a spark,

&c., as also to strike the fingers with which we touch the top or

bottom of the column, with several small snaps, the fingers being

wetted with water. But if to the 20 sets of triplets of the plates be

added 20 or 30 more, disposed in the same order, the actions of the

extended pile will be much stronger, and be felt through the arms up to

the shoulders; and by continuing the touchings, the pains in the hands

become insupportable.

M. Volta constructs and combines his apparatus in various ways and

forms, more or less powerful, convenient or amusing. One is as follows

(Fig. 1, pl. 13,), which he calls a _couronne de tasses_. He

disposes in a row a number of cups of wood, or earth, or glass, or

any thing but metal, half filled with pure water, or salt water or

lye; these are all made to communicate in a kind of chain, by several

metallic arcs of which one arm or link, Aa, or only the extremity A,

immersed in one of the cups, is of copper, or of copper silvered,

and the other Z, immersed in the following cup, is of tin, or rather

of zinc, the other two being soldered together near the crown of

the arch. It is evident that a series of these cups, thus connected

together, either in a straight or curved line, by the two metals and

the intermediate liquid, is similar to the pillar or pile before

described, and consequently will exhibit similar effects. Thus, to

produce commotion or sensation in the hands and arms, we need only dip

one hand into one of the cups and the finger of the other hand into

another cup, sufficiently far from the former; and the action will be

so much the stronger as the two cups are farther asunder, or have the

more intermediate cups; and consequently the greatest by touching the

first and the last in the chain.

* * * * *

M. Volta concludes with various remarks and cautions in using this

instrument; showing that it is perpetual in its virtue, renewing its

charge spontaneously, and serving most of the purposes of the ordinary

electrical machines, and even affecting and manifesting its power by

most of the human senses, viz. feeling, tasting, hearing, and seeing.

FOOTNOTES:

[Footnote 20: From the _Transactions of the Royal Society of

London_.]

XIX

PIERRE SIMON LAPLACE

1749-1827

_Pierre Simon Laplace, born at Beaumont-en-Auge, Normandy, March

28, 1749, became a teacher of mathematics at Beaufort before he was

eighteen years old. He gained d’Alembert’s attention by a letter

which he wrote to him on the principles of mathematics. After 1770

he engaged with Lagrange in determining the permanency of the solar

system by studying its perturbations and interactions, and finally

suggested how these changes were periodic. His monumental work, in five

volumes, “Mechanics of the Heavens” (1799-1825), gave a comprehensive

description of the movements of the solar system, and his “System of

the World” proposed the nebular theory of the origin of the universe.

His researches were important in the development of modern astronomy

because he substituted a dynamic for the descriptive point of view. He

died at Arcueil, March 5, 1827._

THE NEBULAR HYPOTHESIS[21]

Buffon is the only individual that I know of, who, since the discovery

of the true system of the world, endeavoured to investigate the origin

of the planets and satellites. He supposed that a comet, by impinging

on the Sun, carried away a torrent of matter, which was reunited far

off, into globes of different magnitudes and at different distances

from this star. These globes, when they cool and become hardened,

are the planets and their satellites. This hypothesis satisfies the

first of the five preceding phenomena[22]; for it is evident that all

bodies thus formed should move very nearly in the plane which passes

through the centre of the Sun, and through the direction of the torrent

of matter which has produced them: but the four remaining phenomena

appear to me inexplicable on this supposition. Indeed, the absolute

motion of the molecules of a planet ought to be in the same direction

as the motion of the centre of gravity; but it by no means follows

from this, that the motion of rotation of a planet should be also in

the same direction. Thus the Earth may revolve from east to west, and

yet the absolute motion of each of its molecules may be directed from

west to east. This observation applies also to the revolution of the

satellites, of which the direction in the same hypothesis, is not

necessarily the same as that of the motion of projection of the planets.

The small eccentricity of the planetary orbits is a phenomenon,

not only difficult to explain on this hypothesis, but altogether

inconsistent with it. We know from the theory of central forces, that

if a body which moves in a re-entrant orbit about the Sun, passes

very near the body of the Sun, it will return constantly to it, at

the end of each revolution. Hence it follows that if the planets were

originally detached from the Sun, they would touch it, at each return

to this star; and their orbits, instead of being nearly circular,

would be very eccentric. Indeed it must be admitted that a torrent

of matter detached from the Sun, cannot be compared to a globe which

just skims by its surface; from the impulsions which the parts of this

torrent receive from each other, combined with their mutual attraction,

they may, by changing the direction of their motions, increase the

distances of their perihelions from the Sun. But their orbits should

be extremely eccentric, or at least all the orbits would not be q. p.

circular, except by the most extraordinary chance. Finally, no reason

can be assigned on the hypothesis of Buffon, why the orbits of more

than one hundred comets, which have been already observed, should be

all very eccentric. The hypothesis, therefore, is far from satisfying

the preceding phenomena. Let us consider whether we can assign the true

cause.

Whatever may be its nature, since it has produced or influenced the

direction of the planetary motions, it must have embraced them all

within the sphere of its action; and considering the immense distance

which intervenes between them, nothing could have effected this but

a fluid of almost indefinite extent. In order to have impressed on

them all a motion q. p. circular and in the same direction about the

Sun, this fluid must environ this star, like an atmosphere. From a

consideration of the planetary motions, we are therefore brought to

the conclusion, that in consequence of an excessive heat, the solar

atmosphere originally extended beyond the orbits of all the planets,

and that it has successively contracted itself within its present

limits.

In the primitive state in which we have supposed the Sun to be, it

resembles those substances which are termed nebulæ, which, when seen

through telescopes, appear to be composed of a nucleus, more or less

brilliant, surrounded by a nebulosity, which, by condensing on its

surface, transforms it into a star. If all the stars are conceived to

be similarly formed, we can suppose their anterior state of nebulosity

to be preceded by other states, in which the nebulous matter was more

or less diffuse, the nucleus being at the same time more or less

brilliant. By going back in this manner, we shall arrive at a state

of nebulosity so diffuse, that its existence can with difficulty be

conceived.

For a considerable time back, the particular arrangement of some stars

visible to the naked eye, has engaged the attention of philosophers.

Mitchel remarked long since how extremely improbable it was that the

stars composing the constellation called the Pleiades, for example,

should be confined within the narrow space which contains them, by the

sole chance of hazard; from which he inferred that this group of stars,

and the similar groups which the heavens present to us, are the effects

of a primitive law of nature. These groups are a general result of the

condensation of nebulæ of several nuclei; for it is evident that the

nebulous matter being perpetually attracted by these different nuclei,

ought at length to form a group of stars, like to that of the Pleiades.

The condensation of nebulæ consisting of two nuclei, will in like

manner form stars very near to each other, revolving the one about the

other like to the double stars, whose respective motions have been

already recognized.

But in what manner has the solar atmosphere determined the motions of

rotation and revolution of the planets and satellites? If these bodies

had penetrated deeply into this atmosphere, its resistance would cause

them to fall on the Sun. We may therefore suppose that the planets

were formed at its successive limits, by the condensation of zones of

vapours, which it must, while it was cooling, have abandoned in the

plane of its equator.

Let us resume the results which we have given in the tenth chapter of

the preceding book. The Sun’s atmosphere cannot extend indefinitely;

its limit is the point where the centrifugal force arising from the

motion of rotation balances the gravity; but according as the cooling

contracts the atmosphere, and condenses the molecules which are near

to it, on the surface of the star, the motion of rotation increases;

for, in virtue of the principle of areas, the sum of the areas

described by the _radius vector_ of each particle of the Sun and

its atmosphere, and projected on the plane of its equator, is always

the same. Consequently the rotation ought to be quicker, when these

particles approach to the centre of the Sun. The centrifugal force

arising from this motion becoming thus greater; the point where the

gravity is equal to it, is nearer to the centre of the Sun. Supposing,

therefore, what is natural to admit, that the atmosphere extended at

any epoch as far as this limit, it ought, according as it cooled,

to abandon the molecules, which are situated at this limit, and at

the successive limits produced by the increased rotation of the Sun.

These particles, after being abandoned, have continued to circulate

about this star, because their centrifugal force was balanced by their

gravity. But as this equality does not obtain for these molecules

of the atmosphere which are situated on the parallels to the Sun’s

equator, these have come nearer by their gravity to the atmosphere

according as it condensed, and they have not ceased to belong to it

inasmuch as by their motion, they have approached to the plane of this

equator.

Let us now consider the zones of vapours, which have been successively

abandoned. These zones ought, according to all probability, to form by

their condensation, and by the mutual attraction of their particles,

several concentrical rings of vapours circulating about the Sun. But

mutual friction of the molecules of each ring ought to accelerate

some and retard others, until they all had acquired the same angular

motion. Consequently the real velocities of the molecules which are

farther from the Sun, ought to be greatest. The following cause ought

likewise to contribute to this difference of velocities: The most

distant particles of the Sun, and which, by the effects of cooling

and condensation, have collected so as to constitute the superior

part of the ring, have always described areas proportional to the

times, because the central force by which they are actuated has been

constantly directed to this star; but this constancy of areas requires

an increase of velocity, according as they approach more to each other.

It appears that the same cause ought to diminish the velocity of the

particles, which, situated near the ring, constitute its inferior part.

If all the particles of a ring of vapours continued to condense without

separating, they would at length constitute a solid or a liquid ring.

But the regularity which this formation requires in all the parts of

the ring, and in their cooling, ought to make this phenomenon very

rare. Thus the solar system presents but one example of it; that of the

rings of Saturn. Almost always each ring of vapours ought to be divided

into several masses, which, being moved with velocities which differ

little from each other, should continue to revolve at the same distance

about the Sun. These masses should assume a spheroidical form, with a

rotatory motion in the direction of that of their revolution, because

their inferior particles have a less real velocity than the superior;

they have therefore constituted so many planets in a state of vapour.

But if one of them was sufficiently powerful, to unite successively by

its attraction, all the others about its centre, the ring of vapours

would be changed into one sole spheroidical mass, circulating about

the Sun, with a motion of rotation in the same direction with that

of revolution. This last case has been the most common; however, the

solar system presents to us the first case, in the four small planets

which revolve between Mars and Jupiter, at least unless we suppose

with Olbers, that they originally formed one planet only, which was

divided by an explosion into several parts, and actuated by different

velocities. Now if we trace the changes which a further cooling ought

to produce in the planets formed of vapours, and of which we have

suggested the formation, we shall see to arise in the centre of each

of them, a nucleus increasing continually, by the condensation of the

atmosphere which environs it. In this state, the planet resembles the

Sun in the nebulous state, in which we have first supposed it to be;

the cooling should therefore produce at the different limits of its

atmosphere, phenomena similar to those which have been described,

namely, rings and satellites circulating about its centre in the

direction of its motion of rotation, and revolving in the same

direction on their axes. The regular distribution of the mass of rings

of Saturn about its centre and in the plane of its equator, results

naturally from this hypothesis, and, without it, is inexplicable. Those

rings appear to me to be existing proofs of the primitive extension of

the atmosphere of Saturn, and of its successive condensations. Thus,

the singular phenomena of the small eccentricities of the orbits of the

planets and satellites, of the small inclination of these orbits to the

solar equator, and of the identity in the direction of the motions of

rotation and revolution of all those bodies with that of the rotation

of the Sun, follow the hypothesis which has been suggested, and render

it extremely probable. If the solar system was formed with perfect

regularity, the orbits of the bodies which compose it would be circles,

of which the planes, as well as those of the various equators and

rings, would coincide with the plane of the solar equator. But we may

suppose that the innumerable varieties which must necessarily exist in

the temperature and density of different parts of these great masses,

ought to produce the eccentricities of their orbits, and the deviations

of their motions, from the plane of this equator.

In the preceding hypothesis, the comets do not belong to the solar

system. If they be considered, as we have done, as small nebulæ,

wandering from one solar system to another, and formed by the

condensation of the nebulous matter, which is diffused so profusely

throughout the universe, we may conceive that when they arrive in

that part of space where the attraction of the Sun predominates, it

should force them to describe elliptic or hyperbolic orbits. But

as their velocities are equally possible in every direction, they

must move indifferently in all directions, and at every possible

inclination to the elliptic; which is conformable to observation. Thus

the condensation of the nebulous matter, which explains the motions

of rotation and revolution of the planets and satellites in the same

direction, and in orbits very little inclined to each other, likewise

explains why the motions of the comets deviate from this general law.

The great eccentricity of the orbits of the comets, is also a result of

our hypothesis. If those orbits are elliptic, they are very elongated,

since their greater axes are at least equal to the radius of the sphere

of activity of the Sun. But these orbits may be hyperbolic; and if the

axes of these hyperbolæ are not very great with respect to the mean

distance of the Sun from the Earth, the motion of the comets which

describe them will appear to be sensibly hyperbolic. However, with

respect to the hundred comets, of which the elements are known, not

one appears to move in a hyperbola; hence the chances which assign

a sensible hyperbola are extremely rare relatively to the contrary

chances. The comets are so small, that they only become sensible when

their perihelion distance is inconsiderable. Hitherto this distance

has not surpassed twice the diameter of the Earth’s orbit, and most

frequently, it has been less than the radius of this orbit. We may

conceive, that in order to approach so near to the Sun, their velocity

at the moment of their ingress within its sphere of activity, must have

an intensity and direction confined within very narrow limits. If we

determine by the analysis of probabilities, the ratio of the chances

which in these limits, assign a sensible hyperbola to the chances which

assign an orbit, which may without sensible error be confounded with a

parabola, it will be found that there is at least six thousand to unity

that a nebula which penetrates within the sphere of the Sun’s activity

so as to be observed, will either describe a very elongated ellipse,

or an hyperbola, which, in consequence of the magnitude of its axis

will be as to sense confounded with a parabola in the part of its orbit

which is observed. It is not therefore surprising that hitherto no

hyperbolic motions have been recognized.

The attraction of the planets, and perhaps also the resistance of the

ethereal media, ought to change several cometary orbits into ellipses,

of which the greater axes are much less than the radius of the sphere

of the solar activity. It is probable that such a change was produced

in the orbit of the comet of 1759, the greater axis of which was not

more than thirty-five times the distance of the Sun from the Earth. A

still greater change was produced in the orbits of the comets of 1770

and of 1805.

If in the zones abandoned by the atmosphere of the Sun, there are any

molecules too volatile to be united to each other, or to the planets,

they ought in their circulation about this star to exhibit all the

appearances of the zodiacal light, without opposing any sensible

resistance to the different bodies of the planetary system, both on

account of their great rarity and also because their motion is very

nearly the same as that of the planets which they meet.

An attentive examination of all the circumstances of this system

renders our hypothesis still more probable. The primitive fluidity of

the planets is clearly indicated by the compression of their figure,

conformably to the laws of the mutual attraction of their molecules; it

is moreover demonstrated by the regular diminution of gravity, as we

proceed from the equator to the poles. This state of primitive fluidity

to which we are conducted by astronomical phenomena, is also apparent

from those which natural history points out. But in order fully to

estimate them, we should take into account the immense variety of

combinations formed by all the terrestial substances which were mixed

together in a state of vapour, when the depression of their temperature

enabled their elements to unite; it is necessary likewise to consider

the wonderful changes which this depression ought to cause in the

interior and at the surface of the earth, in all its productions, in

the constitution and pressure of the atmosphere, in the ocean, and in

all substances which it held in a state of solution. Finally, we should

take into account the sudden changes, such as great volcanic eruptions,

which must at different epochs have deranged the regularity of these

changes. Geology, thus studied under the point of view which connects

it with astronomy, may, with respect to several objects, acquire both

precision and certainty.

One of the most remarkable phenomena of the solar system is the

rigorous equality which is observed to subsist between the angular

motions of rotation and revolution of each satellite. It is infinity to

unity that this is not the effect of hazard. The theory of universal

gravitation makes infinity to disappear from this improbability, by

shewing that it is sufficient for the existence of this phenomenon,

that at the commencement these motions did not differ much. Then,

the attraction of the planet would establish between them a perfect

equality; but at the same time it has given rise to a periodic

oscillation in the axis of the satellite directed to the planet, of

which oscillation the extent depends on the primitive difference

between these motions. As the observations of Mayer on the libration

of the Moon, and those which Bouvard and Nicollet made for the

same purpose, at my request, did not enable us to recognize this

oscillation; the difference on which it depends must be extremely

small, which indicates with every appearance of probability the

existence of a particular cause, which has confined this difference

within very narrow limits, in which the attraction of the planet might

establish between the mean motions of rotation and revolution a rigid

equality, which at length terminated by annihilating the oscillation

which arose from this equality. Both these effects result from our

hypothesis; for we may conceive that the Moon, in a state of vapour,

assumed in consequence of the powerful attraction of the earth the

form of an elongated spheroid, of which the greater axis would be

constantly directed towards this planet, from the facility with which

the vapours yield to the slightest force impressed upon them. The

terrestrial attraction continuing to act in the same manner, while

the Moon is in a state of fluidity, ought at length, by making the

two motions of this satellite to approach each other, to cause their

difference to fall within the limits, at which their rigorous equality

commences to establish itself. Then this attraction should annihilate,

by little and little, the oscillation which this equality produced on

the greater axis of the spheroid directed towards the earth. It is in

this manner that the fluids which cover this planet, have destroyed by

their friction and resistance the primitive oscillations of its axis

of rotation, which is only now subject to the nutation resulting from

the actions of the Sun and Moon. It is easy to be assured that the

equality of the motions of rotation and revolution of the satellites

ought to oppose the formation of rings and secondary satellites, by the

atmospheres of these bodies. Consequently observation has not hitherto

indicated the existence of any such. The motions of the three first

satellites of Jupiter present a phenomenon still more extraordinary

than the preceding; which consists in this, that the mean longitude of

the first, minus three times that of the second, plus twice that of

the third, is constantly equal to two right angles. There is the ratio

of infinity to one, that this equality is not the effect of chance.

But we have seen, that in order to produce it, it is sufficient if at

the commencement, the mean motions of these three bodies approached

very near to the relation which renders the mean motion of the first,

minus three times that of the second, plus twice that of the third,

equal to nothing. Then their mutual attraction rendered this ratio

rigorously exact, and it has moreover made the mean longitude of the

first minus three times that of the second, plus twice that of the

third, equal to a semicircumference. At the same time, it gave rise to

a periodic inequality, which depends on the small quantity, by which

the mean motions originally deviated from the relation which we have

just announced. Notwithstanding all the care Delambre took in his

observations, he could not recognize this inequality, which, while it

evinces its extreme smallness, also indicates, with a high degree of

probability, the existence of a cause which makes it to disappear. In

our hypothesis, the satellites of Jupiter, immediately after their

formation, did not move in a perfect vacuo; the less condensable

molecules of the primitive atmospheres of the Sun and planet would

then constitute a rare medium, the resistance of which being different

for each of the stars, might make the mean motions to approach by

degrees to the ratio in question; and when these movements had thus

attained the conditions requisite, in order that the mutual attraction

of the three satellites might render this relation accurately true, it

perpetually diminished the inequality which this relation originated,

and eventually rendered it insensible. We cannot better illustrate

these effects than by comparing them to the motion of a pendulum,

which, actuated by a great velocity, moves in a medium, the resistance

of which is inconsiderable. It will first describe a great number of

circumstances; but at length its motion of circulation perpetually

decreasing, it will be converted into an oscillatory motion, which

itself diminishing more and more, by the resistance of the medium, will

eventually be totally destroyed, and then the pendulum, having attained

a state of repose, will remain at rest for ever.

FOOTNOTES:

[Footnote 21: Translated from _Exposition du Système du Monde_,

(Paris, 1796).]

[Footnote 22: viz: “The motions of the planets in the same direction,

and very nearly in the same plane; the motions of the satellites

in the same direction as those of the planets; the motions of the

rotation of these different bodies and also of the sun, in the same

direction as their motions of projection, and in planes very little

inclined to each other; the small eccentricity of the orbits of the

comets and satellites; finally, the great eccentricity of the orbits

of the comets, their inclinations being at the same time entirely

indeterminate.”]

XX

EDWARD JENNER

1749-1823

_Edward Jenner, born May 17, 1749, at Berkeley, Gloucestershire,

England, studied surgery under John Hunter at London, and returned

to his native town to practise. Having learned, about 1796, that

milk-maids who had caught the cow-pox were immune from small-pox, he

began at once to make investigations and to conduct experiments. This

led to his “Inquiry,” published in 1798, in which he made public his

theory of vaccination. His discovery created widespread interest, but

although the theory at once met with the most virulent criticism,

vaccination was soon widely accepted. By 1801, ten thousand persons

were vaccinated in England, and the beneficent results justified its

wide adoption. He died of apoplexy, January 26, 1823._

THE THEORY OF VACCINATION[23]

The deviation of Man from the state in which he was originally placed

by Nature seems to have proved to him a prolific source of Diseases.

From the love of splendour, from the indulgences of luxury, and from

his fondness for amusement, he has familiarised himself with a great

number of animals, which may not originally have been intended for his

associates.

The Wolf, disarmed of ferocity, is now pillowed in the lady’s lap. The

Cat, the little Tyger of our island, whose natural home is the forest,

is equally domesticated and caressed. The Cow, the Hog, the Sheep, and

the Horse, are all, for a variety of purposes, brought under his care

and dominion.

There is a disease to which the Horse, from his state of

domestication, is frequently subject. The Farriers have termed it the

Grease. It is an inflammation and swelling in the heel, from which

issues matter possessing properties of a very peculiar kind, which

seems capable of generating a disease in the Human Body (after it has

undergone the modification which I shall presently speak of), which

bears so strong a resemblance to the Small-pox that I think it highly

probable it may be the source of that disease.

In this Dairy Country a great number of Cows are kept, and the office

of milking is performed indiscriminately by Men and Maid Servants. One

of the former having been appointed to apply dressings to the heels

of a Horse affected with the Grease, and not paying due attention to

cleanliness, incautiously bears his part in milking the Cows, with some

particles of the infectious matter adhering to his fingers. When this

is the case, it commonly happens that a disease is communicated to

the Cows, and from the Cows to the Dairy-maids, which spreads through

the farm until most of the cattle and domestics feel its unpleasant

consequences. This disease has obtained the name of the Cow-pox. It

appears on the nipples of the Cows in the form of irregular pustules.

At their first appearance they are commonly of a palish blue, or

rather of a colour somewhat approaching to livid, and are surrounded

by an erysipelatous inflammation. These pustules, unless a timely

remedy be applied, frequently degenerate into phagedenic ulcers, which

prove extremely troublesome. The animals become indisposed, and the

secretion of milk is much lessened. Inflamed spots now begin to appear

on different parts of the hands of the domestics employed in milking,

and sometimes on the wrists, which quickly run on to suppuration, first

assuming the appearance of the small vesications produced by a burn.

Most commonly they appear about the joints of the fingers, and at their

extremities; but whatever parts are affected, if the situation will

admit, these superficial suppurations put on a circular form, with

their edges more elevated than their centre, and of a colour distantly

approaching to blue. Absorption takes place, and tumours appear in

each axilla. The system becomes affected--the pulse is quickened; and

shiverings, with general lassitude and pains about the loins and limbs,

with vomiting, come on. The head is painful, and the patient is now

and then even affected with delirium. These symptoms, varying in their

degrees of violence, generally continue from one day to three or four,

leaving ulcerated sores about the hands, which, from the sensibility of

the parts, are very troublesome, and commonly heal slowly, frequently

becoming phagedenic, like those from whence they sprung. The lips,

nostrils, eyelids, and other parts of the body, are sometimes affected

with sores; but these evidently arise from their being needlessly

rubbed or scratched with the patient’s infected fingers. No eruptions

on the skin have followed the decline of the feverish symptoms in any

instance that has come under my inspection, one only excepted, and in

this case a very few appeared on the arms: they were very minute, of a

vivid red colour, and soon died away without advancing to maturation;

so that I cannot determine whether they had any connection with the

preceding symptoms.

Thus the disease makes its progress from the Horse to the nipple of the

Cow, and from the Cow to the Human Subject.

Morbid matter of various kinds, when absorbed into the system, may

produce effects in some degree similar; but what renders the Cow-pox

virus so extremely singular is, that the person who has been thus

affected is forever after secure from the infection of the Small-pox;

neither exposure to the _variolous effluvia_, nor the insertion of

the matter into the skin producing this distemper.

[I shall now conclude this Inquiry with some general observations on

the subject, and on some others which are interwoven with it.]

Although I presume it may be unnecessary to produce further testimony

in support of my assertion “that Cow-pox protects the human

constitution from the infection of the Small-pox,” yet it affords me

considerable satisfaction to say that Lord Somerville, the president of

the Board of Agriculture, to whom this paper was shown by Sir Joseph

Banks, has found upon inquiry that the statements were confirmed by

the concurring testimony of Mr. Dolland, a surgeon, who resides in a

dairy country remote from this, in which these observations were made.

With respect to the opinion adduced “that the source of the infection

is a peculiar morbid matter arising in the horse,” although I have not

been able to prove it from actual experiments conducted immediately

under my own eye, yet the evidence I have adduced appears sufficient to

establish it.

They who are not in the habit of conducting experiments may not be

aware of the coincidence of circumstances necessary for their being

managed so as to prove perfectly decisive; nor how often men engaged in

professional pursuits are liable to interruptions which disappoint them

almost at the instant of their being accomplished.

[However, I feel no room for hesitation respecting the common origin

of the disease, being well convinced that it never appears among the

cows (except it can be traced to a cow introduced among the general

herd which has been previously infected, or to an infected servant),

unless they have been milked by someone who, at the same time, has the

care of a horse affected with diseased heels.

The spring of 1797, which I intended particularly to have devoted

to the completion of this investigation, proved, from its dryness,

remarkably adverse to my wishes; for it frequently happens, while

the farmers’ horses are exposed to the cold rains which fall at that

season that their heels become diseased, and no Cow-pox then appeared

in the neighbourhood.]

The active quality of the virus from the horses’ heels is greatly

increased after it has acted on the nipples of the cow, as it rarely

happens that the horse affects his dresser with sores, and as rarely

that a milk-maid escapes the infection when she milks infected cows.

It is most active at the commencement of the disease, even before it

has acquired a pus-like appearance; indeed I am not confident whether

this property in the matter does not entirely cease as soon as it is

secreted in the form of pus. I am induced to think it does cease,

and that it is the thin darkish-looking fluid only, oozing from the

newly-formed cracks in the heels, similar to what sometimes appears

from erysipelatous blisters, which gives the disease. Nor am I certain

that the nipples of the cows are at all times in a state to receive

the infection. The appearance of the disease in the spring and the

early part of the summer, when they are disposed to be affected with

spontaneous eruptions so much more frequently than at other seasons,

induces me to think that the virus from the horse must be received

upon them when they are in this state, in order to produce effects;

experiments, however, must determine these points. But it is clear that

when the Cow-pox virus is once generated, that the cows cannot resist

the contagion, in whatever state their nipples may chance to be, if

they are milked with an infected hand.

Whether the matter, either from the cow or the horse, will affect the

sound skin of the human body, I cannot positively determine; probably

it will not, unless on those parts where the cuticle is extremely thin,

as on the lips for example. I have known an instance of a poor girl

who produced an ulceration on her lip by frequently holding her finger

to her mouth to cool the raging of a Cow-pox sore by blowing upon it.

The hands of the farmers’ servants here, from the nature of their

employments, are constantly exposed to those injuries which occasion

abrasions of the cuticle, to punctures from thorns and such like

accidents; so that they are always in a state to feel the consequences

of exposure to infectious matter.

[It is singular to observe that the Cow-pox virus, although it renders

the constitution unsusceptible of the variolous, should, nevertheless,

leave it unchanged with respect to its own action. I have already

produced an instance to point out this, and shall now corroborate it

with another.

Elizabeth Wynne, who had the Cow-pox in the year 1759, was inoculated

with variolous matter, without effect, in the year 1797, and again

caught the Cow-pox in the year 1798. When I saw her, which was on the

8th day after she received the infection, I found her infected with

general lassitude, shiverings, alternating with heat, coldness of the

extremities, and a quick and irregular pulse. These symptoms were

preceded by a pain in the axilla.]

It is curious also to observe that the virus, which with respect to

its effects is undetermined and uncertain previously to its passing

from the horse through the medium of the cow, should then not only

become more active, but should invariably and completely possess those

specific properties which induce in the human constitution symptoms

similar to those of the variolous fever, and effect in it that peculiar

change which forever renders it unsusceptible of the variolous

contagion.

May it not then be reasonably conjectured that the source of the

Small-pox is morbid matter of a peculiar kind, generated by a disease

in the horse, and that accidental circumstances may have again and

again arisen, still working new changes upon it, until it has acquired

the contagious and malignant form under which we now commonly see it

making its devastations amongst us? And, from a consideration of the

change which the infectious matter undergoes from producing a disease

on the cow, may we not conceive that many contagious diseases, now

prevalent among us, may owe their present appearance not to a simple,

but to a compound origin? For example, is it difficult to imagine that

the measles, scarlet fever, and the ulcerous sore throat with a spotted

skin, have all sprung from the same source, assuming some variety in

their forms according to the nature of their new combinations? The same

question will apply respecting the origin of many other contagious

diseases, which bear a strong analogy to each other.

There are certainly more forms than one, without considering the common

variation between the confluent and distinct, in which the Small-pox

appears in what is called the natural way. About seven years ago a

species of Small-pox spread through many of the towns and villages of

this part of Gloucestershire: it was of so mild a nature that a fatal

instance was scarcely ever heard of, and consequently so little dreaded

by the lower orders of the community that they scrupled not to hold the

same intercourse with each other as if no infectious disease had been

present among them. I never saw nor heard of an instance of its being

confluent. The most accurate manner, perhaps, in which I can convey

an idea of it, is, by saying that had fifty individuals been taken

promiscuously and infected by exposure to this contagion, they would

have had as mild and light a disease as if they had been inoculated

with variolous matter in the usual way. The harmless manner in which it

showed itself could not arise from any peculiarity either in the season

or the weather, for I watched its progress upwards of a year without

perceiving any variation in its general appearance. I consider it then

as a variety of the Small-pox.

[In some of the preceding cases I have noticed the attention that was

paid to the state of the variolous matter previous to the experiment

of inserting it into the arms of those who had gone through the

Cow-pox. This I conceived to be of great importance in conducting

these experiments, and were it always properly attended to by those

who inoculate for the Small-pox, it might prevent much subsequent

mischief and confusion. With the view of enforcing so necessary a

precaution, I shall take the liberty of digressing so far as to

point out some unpleasant facts relative to mismanagement in this

particular, which have fallen under my own observation.]

A medical gentleman (now no more), who for many years inoculated

in this neighbourhood, frequently preserved the variolous matter

intended for his use, on a piece of lint or cotton, which, in its

fluid state, was put into a vial, corked, and conveyed into a warm

pocket; a situation certainly favourable for speedily producing

putrefaction in it. In this state (not infrequently after it had been

taken several days from the pustules) it was inserted into the arms

of his patients, and brought on inflammation of the incised parts,

swellings of the axillary glands, fever, and sometimes eruptions. But

what was this disease? Certainly not the Small-pox; for the matter

having from putrefaction lost, or suffered a derangement in its

specific properties, was no longer capable of producing that malady,

those who had been inoculated in this manner being as much subject

to the contagion of the Small-pox, as if they had never been under

the influence of this artificial disease; and many, unfortunately,

fell victims to it, who thought themselves in perfect security. The

same unfortunate circumstance of giving a disease, supposed to be the

Small-pox, with inefficacious variolous matter, having occurred under

the direction of some other practitioners within my knowledge, and

probably from the same incautious method of securing the variolous

matter, I avail myself of this opportunity of mentioning what I

conceive to be of great importance; and, as a further cautionary hint,

I shall again digress so far as to add another observation on the

subject of Inoculation.

Whether it be yet ascertained by experiment, that the quantity of

variolous matter inserted into the skin makes any difference with

respect to the subsequent mildness or violence of the disease, I know

not; but I have the strongest reason for supposing that if either the

punctures or incisions be made so deep as to go through it, and wound

the adipose membrane, that the risk of bringing on a violent disease is

greatly increased. I have known an inoculator, whose practice was “to

cut deep enough (to use his own expression) to see a bit of fat,” and

there to lodge the matter. The great number of bad cases, independent

of inflammations and abscesses on the arms, and the fatality which

attended this practice was almost inconceivable; and I cannot account

for it on any other principle than that of the matter being placed in

this situation instead of the skin.

At what period the Cow-pox was first noticed here is not upon record.

Our oldest farmers were not unacquainted with it in their earliest

days, when it appeared among their farms without any deviation from

the phenomena which it now exhibits. Its connection with the Small-pox

seems to have been unknown to them. Probably the general introduction

of inoculation first occasioned the discovery.

Its rise in this country may not have been of very remote date, as the

practice of milking cows might formerly have been in the hands of women

only; which I believe is the case now in some other dairy countries,

and consequently that the cows might not in former times have been

exposed to the contagious matter brought by the men servants from the

heels of horses. Indeed a knowledge of the source of the infection is

new in the minds of most of the farmers in this neighbourhood, but it

has at length produced good consequences; and it seems probable from

the precautions they are now disposed to adopt, that the appearance

of the Cow-pox here may either be entirely extinguished or become

extremely rare.

Should it be asked whether this investigation is a matter of mere

curiosity, or whether it tends to any beneficial purpose, I should

answer that, notwithstanding the happy effects of inoculation, with

all the improvements which the practice has received since its first

introduction into this country, it not very infrequently produces

deformity of the skin, and sometimes, under the best management, proves

fatal.

These circumstances must naturally create in every instance some degree

of painful solicitude for its consequences. But as I have never known

fatal effects arise from the Cow-pox, even when impressed in the most

unfavourable manner, producing extensive inflammations and suppurations

on the hands; and as it clearly appears that this disease leaves the

constitution in a state of perfect security from the infection of

the Small-pox, may we not infer that a mode of inoculation may be

introduced preferable to that at present adopted, especially among

those families which, from previous circumstances, we may judge to be

predisposed to have the disease unfavourably? It is an excess in the

number of pustules which we chiefly dread in the Small-pox; but, in

the Cow-pox, no pustules appear, nor does it seem possible for the

contagious matter to produce the disease from effluvia, or by any other

means than contact, and that probably not simply between the virus and

the cuticle; so that a single individual in a family might at any time

receive it without the risk of infecting the rest, or of spreading a

distemper that fills a country with terror.

[Several instances have come under my observation which justify the

assertion that the disease cannot be propagated by effluvia. The first

boy whom I inoculated with the matter of Cow-pox slept in a bed while

the experiment was going forward, with two children who had never gone

through either that disease or the Small-pox, without infecting either

of them.

A young woman who had the Cow-pox to a great extent, several sores

which maturated having appeared on the hands and wrists, slept in the

same bed with a fellow-dairymaid, who never had been infected with

either the Cow-pox or the Small-pox, but no indisposition followed.

Another instance has occurred of a young woman on whose hands were

several large suppurations from the Cow-pox, who was at the same time

a daily nurse to an infant, but the complaint was not communicated to

the child.]

In some other points of view the inoculation of this disease appears

preferable to the variolous inoculation.

In constitutions predisposed to scrofula, how frequently we see the

inoculated Small-pox rouse into activity that distressful malady.

This circumstance does not seem to depend on the manner in which the

distemper has shown itself, for it has as frequently happened among

those who have had it mildly, as when it has appeared in the contrary

way. There are many, who from some peculiarity in the habit resist the

common effects of variolous matter inserted into the skin, and who

are in consequence haunted through life with the distressing idea of

being insecure from subsequent infection. A ready mode of dissipating

anxiety originating from such a cause must now appear obvious. And, as

we have seen that the constitution may at any time be made to feel the

fertile attack of Cow-pox, might it not, in many chronic diseases, be

introduced into the system, with the probability of affording relief,

upon well-known physiological principles?

Although I say the system may at any time be made to feel the febrile

attack of Cow-pox, yet I have a single instance before me where the

virus acted locally only, but it is not in the least probable that

the same person would resist the action both of Cow-pox virus and the

variolous.

FOOTNOTES:

[Footnote 23: From _An Inquiry into the Cause and Effects of the

Variolae Vaccinae_.]

XXI

COUNT RUMFORD

1753-1814

_Sir Benjamin Thompson, Count Rumford, was born in Woburn,

Massachusetts, March 26, 1753, a member of an old New England family.

After a very romantic youth and early manhood in which he underwent

many exciting adventures as a British loyalist at the time of the

American Revolution, he was sent to England with despatches by the

British expeditionary authorities and there found employment in the

office of the Secretary of State. After the close of the Revolution

he went to Bavaria, where he became Minister of War and Grand

Chamberlain. In 1791 he was made a count of the Holy Roman Empire. In

1796 President Adams invited him to return to America to become an

inspector of artillery, but he declined; and at about the same time he

became interested in problems of heat, light, and fuel. His suggestions

ultimately became the basis for the doctrine of the conservation of

energy. He died at Auteuil, August 25, 1814._

THE NATURE OF HEAT[24]

After I had long meditated upon a way of putting this interesting

problem entirely out of doubt by a perfectly conclusive experiment, I

thought finally that I had discovered it, and I think so still.

I argued that if the existence of caloric was a fact, it must be

absolutely impossible for a body or for several individual bodies,

which together made one whole, to communicate this substance

continuously to various other bodies by which they were surrounded,

without this substance gradually being entirely exhausted.

A sponge filled with water, and hung by a thread in the middle of a

room filled with dry air, communicates its moisture to the air, it is

true, but soon the water evaporates and the sponge can no longer give

out moisture. On the contrary, a bell sounds without interruption when

it is struck, and gives out its sound as often as we please without the

slightest perceptible loss. Moisture is a substance; sound is not.

It is well known that two hard bodies, if rubbed together, produce

much heat. Can they continue to produce it without finally becoming

exhausted? Let the result of experiment decide this question.

It would be too tedious to describe here in detail all the experiments

which I undertook with a view of answering in a decisive manner this

important and disputed question. They may be found in my memoir, “On

the Source of Heat excited by Friction.” I have had it printed in

the _Philosophical Transactions_ for the year 1798; still these

experiments bear too close a relation to my later researches on heat

for me to omit attempting at least to give the reader a clear idea of

the experiments and of their results.

The apparatus which I used in these investigations is too complicated

to be represented in this place; still it will not be difficult for

the reader to form a conception of the principal experiments and their

results.

Let A be the vertical section of a brass rod which is an inch in

diameter and is fastened in an upright position on a stout block,

B; it is provided at its upper end with a massive hemisphere of the

same metal, three and a half inches in diameter. C is a similar rod,

likewise vertical, to the lower end of which is fastened a similar

hemisphere. Both hemispheres must fit each other in such a way that

both the rods stand in a perfectly straight vertical line.

D is the vertical section of a globular metallic vessel twelve inches

in diameter, which is provided with a cylindrical neck three inches

long and three and three-quarter inches in diameter. The rod A goes

through a hole in the bottom of the vessel, is soldered into the

vessel, and serves as a support to keep it in its proper position.

The centre of the ball, made up of the two hemispheres which lie the

one upon the other, is in the centre of the globular vessel, so that,

if the vessel is filled with water, the water covers the ball as well

as a part of each of the brass rods.

If now the hemispheres be pressed strongly together, and at the same

time the rod C be turned, by some means or other, about its axis,

a very considerable quantity of heat is generated by means of the

friction which takes place between the flat surfaces of the two

hemispheres.

The quantity of the heat excited in this manner is exactly proportional

to the force with which the two surfaces are pressed together, and to

the rapidity of the friction. When this force was equal to the pressure

of ten thousand pounds, and when the rod was turned with such rapidity

about its axis that it revolved thirty-two times a minute, the quantity

of heat generated by the continual rubbing of the two surfaces together

was extraordinarily great. It was equal to the quantity given off by

the flame of nine wax-candles of moderate size all burning together.

The quantity of heat generated in this manner during a given time is

manifestly the same, whether the globular vessel D is filled with

water, and the surfaces of the two hemispheres rub on each other in

this liquid, or whether there is no water in the vessel, and the

apparatus by which the friction is produced is simply surrounded by air.

The source of the heat which is generated by this apparatus is

inexhaustible. As long as the rod C is turned about its axis, so long

will heat be produced by the apparatus, and always to the same amount.

If the globe-shaped vessel D is filled with water, this water becomes

hotter and hotter, and finally begins to boil. I have myself in this

way boiled a considerable quantity of water.

If this experiment is performed in winter when the temperature of the

air is but little above the freezing-point, and if the vessel D is

filled with a mixture of water and pounded ice, the quantity of heat

caused in a given time by the rubbing together of the two surfaces can

be expressed very exactly by the amount of ice melted by this heat.

Since the apparatus affords heat continuously, and always to the same

amount, we can melt in this way as much ice as we please.

But whence comes this heat? This is the contested point, to determine

which was the real aim of the experiment.

It is certain that it comes neither from the decomposition of the

water nor from the decomposition of the air. Various experiments

on this point, which I have described at length in my memoir in

the _Philosophical Transactions_, are more than sufficient to

establish this fact beyond doubt.

Just as little does it come from a change in the capacity for heat

brought about by friction in the metal of which the hemispheres are

composed. This is shown, first, by the continuance and uniformity of

the production of the heat; and, secondly, by an experiment bearing

directly on this point, by which I am convinced that not the slightest

change had taken place in the capacity of the metal for heat.

Just as little does it come from the rods which are attached to

the hemispheres, for these rods were always warm, the hemispheres

communicating heat to them.

Much less could this heat come from the air of the water immediately

surrounding the hemispheres, for the apparatus communicated heat to

both these fluids without cessation.

Whence, then, came this heat? and what is heat actually?

I must confess that it has always been impossible for me to explain

the results of such experiments except by taking refuge in the very

old doctrine which rests on the supposition that heat is nothing but a

vibratory motion taking place among the particles of bodies.

A bell, on being struck, immediately gives forth a sound, and the

oscillations of the air produced by these vibrations forthwith cause a

quivering motion in those bodies with which they come in contact. On

the other hand, a sponge filled with water cannot give off its moisture

to the bodies in its vicinity for any length of time without itself

losing moisture.

A very illustrious philosopher, for whom I have always entertained the

greatest respect, and whom, moreover, I have the good fortune to count

among my most intimate friends, M. Bertholet, has, in his admirable

_Essai de Statique Chimique_, attempted to explain the results

of this investigation, and to reconcile them with that theory of heat

which is founded upon the hypothesis of caloric.

If a man as learned, as honest, as worthy, and as renowned as is

M. Bertholet spares no pains in opposing the errors of a natural

philosopher or chemist, one cannot and dare not keep silence unless he

wishes to acknowledge himself vanquished. If, however, one can produce

proofs--a fortunate thing for all those who find themselves driven to

similar self-vindication--that the objections of M. Bertholet have no

foundation, he has done very much towards establishing beyond doubt the

opinions and facts in question.

I will now endeavor to answer the objections which M. Bertholet has

offered to my explanation of the above-mentioned experiments; and, that

the reader may be in a position to give to these objections their just

value, I will insert them here in the writer’s own words.

“Count Rumford has made a curious experiment with regard to the heat

which may be excited by friction. He causes a blunt borer to revolve

very rapidly (this borer revolved about its axis only thirty-two times

a minute) in a brass cylinder weighing thirteen pounds, English weight

(the cylinder weighed one hundred and thirteen pounds and somewhat

more), and says that he observed that this borer in the course of

two (one and a half) hours, and under a pressure equal to 100 cwt.,

reduced to powder 4145 grains (8-1/2 ounces Troy) of brass, and that

an amount of heat was generated during this operation sufficient

to bring to boil 26.38 pounds of water, previously cooled to the

freezing-point. He asserts that he did not discover the slightest

difference between the specific heat of the metallic dust and that of

the brass which had not experienced the friction. Hence he supposes

that the heat was excited by the pressure alone, and was not at all

due to caloric, as is the opinion of most chemists.

“I will for the present satisfy myself with simply inquiring whether

it necessarily follows from this experiment that we must renounce

entirely the received theory of caloric, according to which it is

regarded as a substance which enters into combination with bodies, or

whether this result cannot be explained in a satisfactory manner by

applying to the case in question those laws of nature in accordance

with which the operations of heat are manifested under other

conditions.

“If the evolution of heat be regarded as a consequence of the decrease

of volume caused by the pressure, then not only the metallic powder,

but also all the rest of the brass cylinder must have contributed,

though not in an equal manner, to this evolution, by the powerful

expansive effort of that portion which experienced the greatest

pressure, and consequently acquired the greatest temperature, without

being able to assume the dimensions proper to this same temperature on

account of the less heated and less expanded parts; consequently there

must have arisen, necessarily, a certain condensation of the metal

in respect of its natural dimensions, which condensation gradually

decreased from the point where the pressure was greatest to the

surface. We may suppose that this operation took place in a similar

manner in all parts of the cylinder.

“As a consequence of this decrease of volume, an amount of caloric was

given out equal to that which would have caused a similar increase

of volume, on the supposition, that is, that the specific heat of

the metal does not change through this range of the scale of the

thermometer, and that the expansions are equal; and this, considering

the range of temperatures and the consequent expansions, is probably

not far from the truth. The entire amount of heat disengaged would

have raised the cylinder to about 180° of Reaumur’s scale; and if

the expansion of brass by heat is equal to that of iron, which has

been found to be 1-75000 for each degree of the thermometer, the 180

degrees would have caused an expansion of 18-75000 in each direction,

and the decrease of volume must have brought about the same degree of

heat if we suppose that the pressure stood in equal relation to this

expansion.

“Now there is a change, and sometimes a very considerable one, wrought

in the specific gravity of a metal, by percussion, by the action of

a fly-wheel, or by the compression of a wire-drawing machine. It

appears, for example, that the specific gravity of platina and of

iron, on being forged, is thus increased by a twentieth part.

“Hence it appears that the experiment of Count Rumford is far from

explaining satisfactorily a property which is well known, and called

in question by no one.

“It is easy, it is true, to arrange side by side in an imposing manner

the phenomena of heat; if, however, you were to say to one who has

little or no knowledge of chemical speculations, ‘Count Rumford’s

cylinder has, in the course of two hours, by means of a violent

friction, afforded all the heat required to dissolve in water, without

changing its temperature, 15 kilogrammes of ice, or as much as 2

hectogrammes (6-1/2 ounces) of oxygen would require [_sic_] in

its combination with phosphorus,’ I do not know at which of these

phenomena he would be most astonished.

“The slight changes which can take place in the amount of combined

caloric have so inconsiderable an influence on the capacity for work

of the caloric within the narrow limits of the thermometric scale,

that it cannot be computed. Moreover, we have not, as yet, adequate

data for determining the nature of the changes in this respect which

take place in a solid body in consequence of the particular condition

of condensation into which it has been brought by means of certain

mechanical force, and by degrees of heat differing greatly from each

other.

“Besides, Rumford, in the experiment to determine the specific heat

of the filings of bell-metal thus obtained, heated them to the

temperature of boiling water. But this extremely elastic heat would

very naturally as soon as left to itself, and especially during the

operation just mentioned, resume that state of expansion and that

capacity for heat which is proper to it at a given temperature, so

that the effect of the pressure to which it has been subjected partly

disappears again, just as a piece of metal which has been hammered

resumes its natural properties on being annealed.”

In reply to these remarks, I will call to mind what follows.

1st. The discovery which I made, that no considerable change had

taken place in the specific heat of the metallic dust produced by the

friction, led me in no way to the supposition that the heat excited

in the experiment could not come from the caloric set free. I only

found that the source of this heat was inexhaustible. To explain this

phenomenon, which has never yet been explained, is the point now in

question, and I do not see how it can be explained except by giving up

altogether the hypothesis adopted in regard to caloric.

2d. If we actually suppose (and it is far from having been proved)

that the simple pressing together of a metal is sufficient to expel

the caloric contained in it; still the explanation of such a natural

phenomenon would be advanced little or none; for since the action of

the force which causes the pressure is continuous, the condensation

of the metal brought about by this force would in a short time reach

its maximum; and if really in this operation ever so much caloric had

been disengaged from the metal, still it would very soon disperse. The

rubbing surfaces, on the contrary, continue to give forth heat, and

that always to the same amount.

3d. In regard to the objection made to the experiment which was

undertaken with a view of determining whether a change had taken place

in the capacity of the metallic dust for heat, this can very readily be

answered, and in such a way that nothing, it seems to me, can be said

against it. If the temperature of boiling water were really sufficient

to give to these small, forcibly condensed particles of metal the

quantity of heat necessary to bring them back to their original

condition as far as their capacity for heat is concerned, then, as the

water by which the apparatus was surrounded finally began to boil,

they must, without doubt, have taken the necessary amount of heat from

this water. If, now, these particles of metal received finally from

the water the caloric which in the beginning they imparted to it,

the question arises, whence came the caloric which served to heat,

not only the water, but also the metal and the objects immediately

surrounding it?

I am far from desiring to deceive anyone by an imposing arrangement

of facts; but the facts in my experiments were so very striking that

it was altogether impossible for me to help instituting comparisons

and making calculations with regard to them which would make them

clear, especially to those not yet sufficiently acquainted with such

investigations.

I will now close my remarks with an entirely new computation. I will

show whether it is probable that the metal could supply all the heat

which was produced by friction in the experiment in question. If we are

to make this supposition, we must, in the first place, allow that all

the heat came directly from the particles of metal which were separated

from the solid mass of metal by the friction; for, since the mass

remained in the same condition throughout the entire experiment, it is

evident that it could contribute in no measure to the effect produced.

We will now inquire how much heat would have been developed if the

experiment had been carried on without cessation, until the whole mass

of metal had been reduced to powder by the friction.

After the experiment had lasted an hour and a half, there were 4145

grains (Troy) of the metallic dust, and during that time an amount of

heat was produced by the friction sufficient to raise 26.58 pounds of

ice-cold water to the boiling point.

Since the mass of metal weighed 113.13 pounds, or 791,190 grains, all

this metal would have been reduced to powder if the experiment had

lasted uninterruptedly, day and night, for 477-1/2 hours, or for 19

days 21-1/2 hours, and during this time an amount of heat would have

been produced sufficient to have raised 5078 pounds of water to the

boiling-point.

Since the metal used in this experiment showed a capacity for heat

which was to that of water as 0.11 to 1, it is evident that this amount

of heat would have been sufficient to raise a mass of the same metal

46,165 pounds in weight through 180 degrees of Fahrenheit’s scale, or

from the temperature of melting ice to that of boiling water.

This amount of heat would be sufficient to melt a mass of metal sixteen

times heavier than that which I used in the experiment.

Is it at all conceivable that such an enormous quantity of caloric

could really be present in this body? But even this supposition would

be by no means sufficient for the explanation of the fact in question,

as I have shown by a decisive experiment that the capacity of the metal

for heat has not sensibly altered.

Whence, then, came the caloric which the apparatus furnished in such

abundance?

I leave this question to be answered by those persons who believe in

the actual existence of caloric.

In my opinion, I have made it sufficiently evident that it was

impossible for it to come from the metallic bodies which were rubbed

together, and I am absolutely unable to imagine how it can have come

from any other object in the neighborhood of the apparatus, for all

these objects received their heat constantly from the apparatus itself.

FOOTNOTES:

[Footnote 24: From _An Enquiry Concerning the Source of Heat Excited

by Friction_ (1798)--_Transactions of the Royal Society of

London_.]

XXII

JOHN DALTON

1766-1844

_John Dalton, son of a weaver, was born in Cumberland,

England, September 5, 1766. After an early life spent in teaching in

elementary schools, in 1793 he became a teacher of mathematics and

philosophy at New College, Manchester. He began his researches into the

combination of gases in 1800 and discovered that gases expanded equally

with the same pressure and heat. He announced his discovery in a paper

read before the Manchester Society in 1801. From further experiments

he derived his theory that gases combined with one another in definite

proportions, and evolved his atomic theory to explain the results.

Awarded the King’s medal in 1822, he was further honored by a pension

granted in 1833. He died May 27, 1844._

THE ATOMIC THEORY[25]

There are three distinctions in the kinds of bodies, or three states,

which have more especially claimed the attention of philosophical

chemists; namely, those which are marked by the terms elastic fluids,

liquids, and solids. A very familiar instance is exhibited to us

in water, of a body which, in certain circumstances, is capable of

assuming all the three states. In steam we recognize a perfectly

elastic fluid, in water a perfect liquid, and in ice a complete solid.

These observations have tacitly led to the conclusion which seems

universally adopted, that all bodies of sensible magnitude, whether

liquid or solid, are constituted of a vast number of extremely small

particles, or atoms of matter bound together by a force of attraction,

which is more or less powerful according to circumstances, and which

as it endeavours to prevent their separation, is very properly called

in that view, attraction of cohesion; but as it collects them from a

dispersed state (as from steam into water) it is called attraction of

aggregation, or more simply, affinity. Whatever names it may go by,

they will signify one and the same power. It is not my design to call

in question this conclusion, which appears completely satisfactory;

but to show that we have hitherto made no use of it, and that the

consequence of the neglect has been a very obscure view of chemical

agency, which is daily growing more so in proportion to the new lights

attempted to be thrown upon it.

The opinions I more particularly allude to, are those of Bertholet

on the Laws of chemical affinity; such as that chemical agency is

proportional to the mass, and that in all chemical unions there exist

insensible gradations in the proportions of the constituent principles.

The inconsistence of these opinions, both with reason and observation,

cannot, I think, fail to strike every one who takes a proper view of

the phenomena.

Whether the ultimate particles of a body, such as water, are all

alike, that is, of the same figure, weight, etc., is a question of

some importance. From what is known, we have no reason to apprehend

a diversity in these particulars: if it does exist in water, it must

equally exist in the elements constituting water, namely, hydrogen and

oxygen. Now it is scarcely possible to conceive how the aggregates

of dissimilar particles should be so uniformly the same. If some of

the particles of water were heavier than others, if a parcel of the

liquid on any occasion were constituted principally of these heavier

particles, it must be supposed to affect the specific gravity of the

mass, a circumstance not known. Similar observations may be made on

other substances. Therefore we may conclude that the ultimate particles

of all homogeneous bodies are perfectly alike in weight, figure, etc.

In other words, every particle of water is like every other particle

of water; every particle of hydrogen is like every other particle of

hydrogen, etc.

FOOTNOTES:

[Footnote 25: From a note entitled _On the Constitution of Bodies_

which Dalton wrote and had incorporated in Thomas Thompson’s _System

of Chemistry_ (3d edition, 1807).]

XXIII

MARIE FRANÇOIS XAVIER BICHAT

1771-1802

_Bichat was born in the French town of Thoirette (Department of

Ain), November 14, 1771. At the University of Lyons he was especially

interested in anatomy, surgery, and natural history. In 1793, because

of the Revolution, he fled to Paris, where he studied under the eminent

surgeon Desault. In 1800 he distinguished between animal and organic

functions and after many dissections he developed, in 1801, his famous

doctrine of tissues. He died July 22, 1802, from injuries received in a

fall._

THE DOCTRINE OF TISSUES[26]

OBJECT OF THE WORK

The general doctrine of this work has not precisely the character of

any of those which have prevailed in medicine. Opposed to that of

Boerhaave, it differs from that of Stahl and those authors who, like

him, refer everything in the living economy to a single principle,

purely speculative, ideal, and imaginary, whether designated by the

name of soul, vital principle, or archeus. The general doctrine of this

work consists in analyzing with precision the properties of living

bodies, in showing that every physiological phenomenon is ultimately

referable to these properties considered in their natural state;

that every pathological phenomenon derives from their augmentation,

diminution, or alteration; that every therapeutic phenomenon has for

its principle the restoration of that part of the natural type, from

which it has been changed; in determining with precision the cases

in which each property is brought into action; in distinguishing

accurately in physiology as well as in medicine, that which is

derived from one, and that which flows from others; in ascertaining by

rigorous induction the natural and morbific phenomena which the animal

properties produce, and those which are derived from the organic;

and in pointing out when the animal sensibility and contractility

are brought into action, and when the organic sensibility and the

sensible or insensible contractility. We shall be easily convinced upon

reflection, that we cannot precisely estimate the immense influence

of the vital properties in the physiological sciences, before we have

considered these properties in the point of view in which I have

presented them. It will be said, perhaps, that this manner of viewing

them is still a theory; I will answer that it is a theory like that

which shows in the physical sciences, gravity, elasticity, affinity,

etc., as the primitive principles of the facts observed in these

sciences. The relation of these properties as causes to the phenomena

as effects, is an axiom so well known in physics, chemistry, astronomy,

etc., at the present day, that it is unnecessary to repeat it. If this

work establishes an analogous axiom in the physiological sciences, its

object will be attained.

OBSERVATIONS UPON THE ORGANIZATION OF ANIMALS

The properties, whose influence we have just analyzed, are not

absolutely inherent in the particles of matter that are the seat of

them. They disappear when these scattered particles have lost their

organic arrangement. It is to this arrangement that they exclusively

belong; let us treat of it here in a general way.

All animals are an assemblage of different organs, which, executing

each a function, concur in their own manner, to the preservation of

the whole. It is several separate machines in a general one, that

constitutes the individual. Now these separate machines are themselves

formed by many textures of a very different nature, and which really

compose the elements of these organs. Chemistry has its simple bodies,

which form, by the combination of which they are susceptible, the

compound bodies; such are caloric, light, hydrogen, oxygen, carbon

azote, phosphorus, etc. In the same way anatomy has its simple

textures, which, by their combinations four with four, six with six,

eight with eight, etc., make the organs. These textures, are, 1st,

the cellular; 2d, the nervous of animal life; 3d, the nervous of

organic life; 4th, the arterial; 5th, the venous; 6th, the texture

of the exhalants; 7th, that of the absorbents and their glands; 8th,

the osseous; 9th, the medullary; 10th, the cartilaginous; 11th, the

fibrous; 12th, the fibro-cartilaginous; 13th, the muscular of animal

life; 14th, the muscular of organic life; 15th, the mucous; 16th, the

serous; 17th, the synovial; 18th, the glandular; 19th, the dermoid;

20th, the epidermoid; 21st, the pilous.

These are the true organized elements of our bodies. Their nature is

constantly the same, wherever they are met with. As in chemistry, the

simple bodies do not alter, notwithstanding the different compound ones

they form. The organized elements of man form the particular object of

this work.

The idea of thus considering abstractly the different simple textures

of our bodies, is not the work of the imagination; it rests upon the

most substantial foundation, and I think it will have a powerful

influence upon physiology as well as practical medicine. Under whatever

point of view we examine them, it will be found that they do not

resemble each other; it is nature and not science that has drawn the

line of distinction between them.

1st. Their forms are everywhere different; here they are flat, there

round. We see the simple textures arranged as membranes, canals,

fibrous fasciæs, etc. No one has the same external character with

another, considered as to their attributes of thickness or size.

These differences of form, however, can only be accidental, and the

same texture is sometimes seen under many different appearances; for

example, the nervous appears as a membrane in the retina, and as cords

in the nerves. This has nothing to do with their nature; it is then

from the organization of the properties that the principal differences

should be drawn.

2dly. There is no analogy in the organization of the simple textures.

We shall see that this organization results from parts that are common

to all, and from those that are peculiar to each; but the common parts

are all differently arranged in each texture. Some unite in abundance

the cellular texture, the blood vessels and the nerves; in others, one

or two of these three common parts are scarcely evident or entirely

wanting. Here there are only the exhalants and absorbents of nutrition;

there the vessels are more numerous for other purposes. The capillary

network, wonderfully multiplied, exists in certain textures; in

others this network can hardly be demonstrated. As to the peculiar

part, which essentially distinguishes the texture, the differences

are striking. Color, thickness, hardness, density, resistance, etc.,

nothing is similar. More inspection is sufficient to show a number of

characteristic attributes of each clearly different from the others.

Here is a fibrous arrangement, there a granulated one; here it is

lamellated, there circular. Notwithstanding these differences, authors

are not agreed as to the limits of the different textures. I have had

recourse, in order to leave no doubt upon this point, to the action

of different re-agents. I have examined every texture, submitted them

to the action of caloric, air, water, the acids, the alkalies, the

neutral salts, etc., drying, putrefaction, maceration, boiling, etc.;

the products of many of these actions have altered in a different

manner each kind of texture. Now it will be seen that the results have

almost all been different, that in these various changes each acts in

a particular way, each gives results of its own, no one resembling

another.

There has been considerable inquiry to ascertain whether the arterial

coats are fleshy, whether the veins are of an analogous nature, etc. By

comparing the results of my experiments upon the different textures,

the question is easily resolved. It would seem at first view that all

these experiments upon the intimate texture of systems answer but

little purpose; I think, however, that they have effected a useful

object, in fixing with precision the limits of each organized texture;

for the nature of these textures being unknown, their differences can

be ascertained only by the different results they furnish.

3rdly. In giving to each system a different organic arrangement,

nature has also endowed them with different properties. You will

see in the subsequent part of this work, that what we call texture

presents degrees indefinitely varying, from the muscles, the skin,

the cellular membrane, etc., which enjoy it in the highest degree,

to the cartilages, the tendons, the bones, etc., which are almost

destitute of it. Shall I speak of the vital properties? See the

animal sensibly predominant in the nerves, contractility of the same

kind particularly marked in the voluntary muscles, sensible organic

contractility, forming the peculiar property of the involuntary,

insensible contractility and sensibility of the same nature, which is

not separated from it more than from the preceding, characterizing

especially the glands, the skin, the serous surfaces, etc., etc. See

each of these simple textures combining, in different degrees, more or

less of these properties, and consequently living with more or less

energy.

There is but little difference arising from the number of vital

properties they have in common; when these properties exist in many,

they take in each a distinctive and peculiar character. This character

is chronic, if I may so express myself, in the bones, the cartilages,

the tendons, etc.; it is acute in the muscles, the skin, the glands,

etc.

Independently of this general difference, each texture has a particular

kind of force, of sensibility, etc. Upon this principle rests the whole

theory of secretion, of exhalation, of absorption, and of nutrition.

The blood is a common reservoir, from which each texture chooses that

which is adapted to its sensibility, to appropriate and keep it, and

afterwards reject it.

Much has been said since the time of Bordeu, of the peculiar life of

each organ, which is nothing else than that particular character which

distinguishes the combination of the vital properties of one organ

from those of another. Before these properties had been analyzed with

exactness and precision, it was clearly impossible to form a correct

idea of this peculiar life. From the recount I have just given of it,

it is evident that the greatest part of the organs being composed of

very different simple textures, the idea of a peculiar life can only

apply to these simple textures, and not to the organs themselves.

Some examples will render the point of doctrine which is important,

more evident. The stomach is composed of the serous, organic muscular,

mucous, and of almost all the common textures, as the arterial, the

venous, etc., which we can consider separately. Now if you should

attempt to describe in a general manner, the peculiar life of the

stomach, it is evidently impossible that you could give a very precise

and exact idea of it. In fact the mucous surface is so different

from the serous, and both so different from the muscular, that by

associating them together, the whole would be confused. The same is

true of the intestines, the bladder, the womb, etc.; if you do not

distinguish what belongs to each of the textures that form the compound

organs, the term peculiar life will offer nothing but vagueness and

uncertainty. This is so true, that oftentimes the same textures

alternately belong or are foreign to their organs. The same portion of

the peritoneum, for example, enters or does not enter, into the gastric

viscera, according to their fulness or vacuity.

Shall I speak of the pectoral organs? What has the life of the

fleshy texture of the heart in common with that of the membrane that

surrounds it? Is not the pleura independent of the pulmonary texture?

Has this texture nothing in common with the membrane that surrounds

the bronchia? Is it not the same with the brain with relation to its

membranes, of the different parts of the eye, the ear, etc.?

When we study a function it is necessary carefully to consider in a

general manner, the compound organ that performs it; but when you

wish to know the properties and life of this organ, it is absolutely

necessary to decompose it. In the same way, if you seek only general

notions of anatomy, you can study each organ as a whole; but it is

essential to separate the textures, if you have a desire to analyze

with accuracy its intimate structure.

CONSEQUENCES OF THE PRECEDING PRINCIPLES RELATIVE TO DISEASE

What I have been saying leads to important consequences, as it respects

those acute or chronic diseases that are local; for those which, like

most fevers, affect almost simultaneously every part, cannot be much

elucidated by the anatomy of systems. The first then will engage our

attention.

Since diseases are only alterations of the vital properties, and each

texture differs from the others in its properties, it is evident that

there must be a difference also in the diseases. In every organ, then,

composed of different textures, one may be diseased, while the others

remain sound; now this happens in a great many cases; let us take the

principal organs, for example.