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great man's history, that sort of detail a manner as to indicate that he had which originates in singular or various been well instructed. Ac his very comadventures. To know at once how to mencement in philosophy, he struck into enlighten his cotemporaries and to be a line before then unknown, and gave esteemed by them; to possess talents, the signal for che arrival of an entirely and yet be respected by criticisın; to new epoch. be rich and possess family honours with. We allude to the Dissertation on Air, out exciting envy; to preserve his health which he laid before the Royal Society and mental powers after long-continued in 1766 :* an article, the object of which and indefatigable labours; are a com- was nothing less than to establish the bination of advantages which so seldom fact, till then never heard of; namely, occur in the life of man, that we cannot that air is not an element; but that there but feel interested in knowing the par. are several kinds of air essentially difticulars of these advantages, and in stu ferent. dying the causes which produced them. From the time of Van HELMONT, pbi

Mr. Cavendish was born in London losophers knew that various bodies exon the 10th of October, 1731. His hale fluids, which resemble air by their father was Lord Charles Cavendish, permanent elasticity, BOYLE soon found likewise a Member of the Royal Soout that they cannot serve for respiraciety, and Trustee of the British Mu- tion; Ilales thought they miglit be ineaseum.

sured ; and conceived the means of effectHis family, which traces its descent ing this point. BROWNRIGG and VENEL from one of the companions of William had shown that certain mineral waters the Conqueror, is amongst the most derive from them their pungent taste: illustrious houses of Great Britain. It Black had discovered, that, by their has, for more than two centuries, be presence, quick-lime is distinguished from longed to the peerage, and William IIT, Jime-stone, as well as are the caustic in 1694, exalted its head to the title of from the common alkalis. MACBRIDE Duke of Devonshire.

at length called the attention of physic It has been observed that in England cians towards thein, by employing them there are more people of quality who se. against putrefaction: but, amidst all these riously apply themselves to the sciences, investigacions, a sufficient discinction bad or to letters, than in other countries. not been made between the different The fact is, that, from the nature of the sorts of airs : it was not generally begovernment, neither birth nor fortune lieved that they were particular subcan confer distinction upon the possessors, stances in their species; and more than unless these are accompanied by talents. one philosopher of renown persisted Hence, it is necessary to `prepare the that they were only common air, altered young nobility for acquiring general by the emanations of the bodies which knowledge, by a proper course of stu- furnished ic; though nobody could predies; and, amongst so many young men cisely point out of what these supposed who have the advantages of a scientific emanations consisted. education, some are always found who Mr. Cavendish, however, gave in his rather choose to employ their faculties in paper; and, in a few pages, he threw searching for imperishable facts, than in such light on the subject, that there was merely supporting the vacillating intes no longer but one opinion. rests of the hour.

He compared, for example, the elastie The whole life of Mr. Cavendish is fluid extracted from lime and the alkalis, a proof that such a preference was im- with that produced by fermentation and planted in his very nature : but domestic putrefaction, as well as with that which example was necessary to confirin, at prevails at the bottom of wells, mines, an early period, this inclination.

and pits; and he showed that they all Lord Charles, his father, was also a possess the same properties, and forin Jover of the sciences, and has left some only one and the same Auid, for which good observations on natural philosoplıy. was afterwards reserved the name of It is probable that he directed the fired air. He ascertained the specific early studies of his son ; but we have gravity of this air, and found it to be no, nocount of the method he adopted always the same, or greater by one-third in bis elementary education, nor even than that of common air; this fact of the first attempts of the young leary explained why fixed air always fills low in the road of science. He appeared in it suddenly, but nevertheless in such * Phil. Trans. 1766. p. 141.

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fiacus,

places, as well as the deleterious effects mentation, and each person endeavoured which it occasions. He discovered that to give reasons for supporting those thethis sort of air has the property of ories which were evidently going to ruin. combining with water, and then dis. The introduction of fixed air amongst the solving lime-stone and iron; which il. acids, by BERGMANN, though it simlustrates the effects of petrifying waters, plified chemistry in a small degree, ap. of stalactites, and of the presence of peared but a slight palliative to the rairon in mineral waters. In short, he dical vice which was now admitted convinced himself that it is precisely The science had remained in this state this same air which is given out on the for the space of seven years, when Lacombustion of charcoal, and which ren. VOISIER received the first light of his ders this kind of combustion so dan. famous doctrine. Haring obtained a gerous.

quantity of fixed air, from the reduction His experiments on inflammable air of metals by carbon, he concluded, that were still more novel and interesting the calcination of metallic substances Before the period in question, scarcely was nothing more than their combination any one had given attention to the nature with fixed air. A year afterwards, BAYER of this fuid, which was known only from reduced calces of mercury without carthe explosions which it sometimes caused bon, in luted vessels, and thus sapped in the mines. Mr. Cavendish, however, the principal foundation of the phlogistic ty treating it like fixed air, proved that theory. Lavoisier next examined the inflammable air is identical, and pose air produced by these experiments with sesses the same properties, whether it be out carbon, and found it respirable; and obtained from the solution of iron, or nearly about the same time, PRIESTLEY from that of zinc or copper : and amongst discovered, that this was precisely the these properties, he particularly proved it part of the atmosphere necessary at once to possess that specific gravity, or other for respiration and combustion. rarity, which renders it nearly ten times LAVOISIER now made his next step. Jighter than common air; and of which He asserted, that respiration, the calcipeculiar quality our brother-member, M. nation of metals, and combustion, are CHARLES, has since made such a notable similar operations, caused by the combi. application, by rendering aërial travel. nations of respirable air; that fixed air is ling safe and easy! In short, we inay the peculiar product of the combustion of say, that, without the discovery of Mr. charcoal; but the phenomena of solu. CAVENDISH, and the application of it by tions, and the inflammable air which apM, CHARLES, the attempt of M. de pears on those occasions, were not yet MONTGOLFIER would scarcely have been explained. It required six more years to practicable, so numerous are the dan- ascertain these points, and Mr. Caves. gers and embarrassments of the aëronaut, DISH had the honour of the discovery. if he be obliged to keep the common air Scheele had observed that, on burndilated by means of fire, as must be the ing inflammable air, he obtained neither case with all the Montgolfier balloons. fixed air nor phlogisticated air; the

The labours of Mr. Cavendishi reepectwhole seemed to disappear. MACQUER, ing airs had, however, far greater con- endeavouring to retain the vapour from sequences, the importance of which was this combustion, observed, with astospeedily discovered. The fact, once nishment, some moisture on the vessels ascertained, that there might exist several he made use of; but he thought with elastic fluids, invariable in their pro. Scheele, that the airs were lost. Mr. perties, and specifically ditferent in their Cavendish, who had in some degree in nature, led to the first investigations of troduced inflamınable air into chemical PRIESTLEY, which made known (wo experiments, was the first to point out new kinds of Auids, phlogistic and nitrous the great part which it would act in the mir. Soon after this discovery, men be- science. Acting, as he did, on his gan to find out in what way the different first discovery, with precision, on a sube airs influenced the phenomena of nature, ject vaguely understood before his time, and to infer, that systems of pliilosophy he deflagrated inflammable air in closed and cheu istry, established without due vessels, by the electric spark, by supregard to such powerful and universal plying gradually as much respirable ait agents, could not be permanent. The as was necessary for the combustion : minds of philosophers, agilared by im- he then found, that the former of these patience and doubts, which formed their principal resource, were in a sort of fer. Philos. Trans, 1784 ; Part I. p. 119.

airs absorbed a certain portion of the which was then called phlogiston, but latter, and that the whole resolved into a which has since been termed azote. quantity of water, equal to the weight of On examining afterwards the product the two airs that had disappeared. from the detonation of nitre by charcoal,

This great phenomenon, which Mr. he found it to consist of this same phloCavendish spent tbree years in confirm- gisticated air and fixed air. It was the ing, was announced to the Royal Society carbon which had given out the latter. on the 14th of January, 1781. Our bro- Consequently the former could only have ther member, the Count de PELUSE, who been furnished by the acid of the nitre. had conceived the same idea, and made Mr. Cavendish was soon enabled to the same experiments as Mr. Cavendish, prove, by direct experiments, the accus communicated the result about the same racy of bis conjecture. On firing, by time to LAVOISIER and M. de LAPLACE, the electric spark, a mixture of atinoIf the combination of the airs give out spheric and phlogisticated airs, he con. water, said M. de Laplace, this must be verted it into nitrous air ; which, of itself, the result of its decomposition, Pbilo changes into an acid by a new addicion sophers then employed themselves in de- of atmospheric air. composing water, in the same manner as Thus the elements of che nitrous'acid they had coinposed it. Lavoisier per. were discovered to be the same as those formed the two operations, with great so. of the atmosphere, only in different prolemnity, before a committee of the Aca. portions; and from ihat time we had demy; and those experiments, having clear ideas of the universal, and till then formed the basis of his new theory, threw incomprehensible, generation of that much light on what had till then escaped acid. notice.

One cannot peruse without a sort of In fact, water being nothing but a com- enthusiasın, the history of this epoch, bination of the two airs, wherever it is the most brilliant which ever occurred found, it will always furnish them by de- to chemistry. Discoveries seemed to cornposition; and, wherever the airs press upon one another. Mr. Cavendish exist, water can be produced from their having colamunicated the experiment he combination. llence, as inflammable had just made on the nitric acid to our air is obtained by metallic solutions, and colleague BERTIOLLET, he received from by a series of other results, the compo- him, in return, post after post, accounts sition of organised beings, and the most of the decomposition of ammonia, in incomplicated changes of their principles flammable, as well as in phlogisticated are effected. In short, from this period, air. For what men, and what an age, was the theory of chemistry was placed upon such a correspondence reserved! immutable bases.

At length, Mr. Cavendish examined Thus, it may be said, that this new them the atmosphere itself; and it produced ory, which has effected so great a revo. on living beings such various effects, that iurior, in the sciences, is indebted for its it was naturally supposed to be very va. origin to a discovery by Mr. CAVENDISH; riable in the proportion of its elements. and that a second discovery, by the same Priestley, who had discovered the pure philosopher, rendered it complete. and respirable air, had also discovered

This gentleman, however, made a the means of ascertaining the quantity of third discovery, which would have been such air io for the respirability of) any sufficient to immortalise him, if the two air whatever. It was only necessary to others had not occurred: it was that of measure the portion of pure air which the composition of the nitrous acid, a was absorbed on mixing it with nitrous substance so useful in the arts, and so air; but his instruments were not at that abundant in nature; a substance about time perfect; notwithstanding the inwhich, before the time of Mr. Cavendishi, provements made in them hy FONTANA. chemists entertained only vague and hy

Mr. Cavendish, by a slight difference pothetical ideas.* .

in the process of making them, gave them From his first experiments on the com- a much greater precision;* and, having bustion of inflamınable air, it occurred to employed them in comparing pure air in him that there was a formation of nitrous different places, and at various times, he acid, and that it would accrue in propor. ascertained a result which was little exţion to the quantity of the air employed, pected; namely, that the quantity of re* Phil. Trans. 1786.

* Philos. Traps. 1745, Part I. p. 106.

spirable

spirable air is erery where the same ; and gave to his labours such a degree of perthat the sineils which so sensibly affect fection, that, even at the present day, our organs, and the miasmata which so nothing can be added to, or abstracted dreadtully assail our system, cannot be from them; although his first reports were destroyed by any chemical means; a published more than forty years ago, and fact, which, though on the first view it is the science to which they relate has unvery discouraging, nevertheless affords to dergone, in the interval, a complete rethe reflecting mind an immense scope, volution ; an advantage which perhaps and exposes, at a vast distance, the sha. no other man has possessed since writdows of sciences which exist not yet forings on the sciences first became general. us, but for which alone it is perhaps re- This rigorous spirit of investigation, inserved to explain to us the hidden secrets troduced into chemistry through the inof those which already prevail.

fuence of Mr. Cavendish, has rendered M. DE HUMBOLDT bes confirmed this as eminent services to this science as bis fact iy the most distant regions, by means discoveries themselves; for it is to liis · of the eudiometer of intlamınable air; system that we are indebted, in a great

and M. Gay Lussac, on ascending in a degree, for those discoveries which he balloon, found it equally true at the did not make. greatest heights which man could reach, About the middle of the eighteenth as it was in the inferior strata of the ale century chemistry seemed to be the only mosphere. Thus these courageous phie asylum for the systems and suppositions losophers always made use of an agent which Newton had driven from philosofound out by Mr. Cavendish, to verify phy. Cavendish and Bergmanı expelled another of his discoveries.

• them from this last resort, and cleaused Such are the ciccumstances which have this Augean stable from the filth of the justly given Mr. Cavendish a place Hermetic philosophy. After them 10amongst chemists. They occupy, in de. body dared to operate otherwise than scription, but a very few pages of print; with determinale quantities, and by but they will outlive many a large vo- keeping an exact account of all kinds of lume: the labour, however, which they products! It is this mode of proceeding once cost, must not be estimated by the which forms the distinguishing characlespace which they now hill.

ristic of moderu chemistry, much more To untie the concealed knot which so than its theories, which, however fiue unites so inany complicated phenomena; they may appear to us, would not perto pursue the same principles, amidst so haps be invulnerable if we were al some many alterations and metamorphoses, future time to succeed in obtaining suband particularly to expose so clearly stances which at present are unknowa what bad for so many centuries escaped to us. the most able of men, and to make these The persevering or rigid spirit of Mr. facts evident to all the world, could only Cavendish was owing to a profound study be the effect of the most persevering and of geometry, of which he likewise made well-directed cogitations. Mr. Caven- direct applications, and sometimes with dish, indeed, was a living proof of the as much success as his researches in truth of the adage of one of his most il cbeinistry, Justrious cotemporaries that genius is Sueli, in particular, is his determination only an additionaliucitement to patience; of the menn density, or, what is the same which is strictly true, when we allude to thing, of the total weight of the globe; the patience of a man of intellect.

an idea which bas at first somethiog in it Another qualification equally laudable, that is terrific, but which is nevertheless was this gentleman's rigid system of ex. reduced to a siiaple mechanical problem. periments. No sophistry, nothing of a Archimedes only wanted a point of sup. doubtful nature, was suffered to pass un- port to enable lin w ove the carih, but elucidated. His perseverance was so this was not necessary to enable Mr. Car well known, that his cotemporaries took vendish to weigh it! pleasure in submitting to him the results Mr. MITCHELL, apother Member of the of their inquiries; being almost certain, Royal Society, who died some time agus thai, if he approved of then, nobody else hau conceived the means of perforining culi amend them. He was, however, this experiment, and had constructed an more severe with himseli, in maiters of apparatus, which was nearly the same * science, than he was towards any other person; and it was this rigid plan which # Phil. Trans, 1798. Part II. p. 469.

CON

our late celleague, M. COULOMB, bad al At first this discovery appeared to conready employed, for measuring the power tradict that of MASKELYNE, in which the of electricity and that of the load-stone. deviation produced by the vicinity of a

A lever six feet long, and having at its mountain, on the plumb line of his ina extremities a little leaden ball, was sus. struments, had made him conclude, that pended horizontally by the middle to a the mean density of the globe was only vertical thread. When the lever had at. four times and a half greater than ibat of tained an equilibrium, and become sta- water. But it is asserted that, these excionary, there was brought towards each periments having been since made with of its ends a great mass of lead, of a more accuracy, their result comes much given weight and diameter: the attrac nearer to that of Mr. Cavendish. tion of the masses on the balls put the This gentleman was also one of the lever in motion, the thread then twisted, first who applied calculation to the theory in order to yield to this action, and of electricity. He performed this task stretching, to return to its former state, before the appearance of the work of it inade the lever describe little horizon- Epinus, but the account of it was not tal ares, as the-ordinary weight: that is printed till afterwards. It is founded on to say, the teraction of the earth causes the same hypothesis; that is to say, on vertical arai, o be described by the peri- one single electric substance, the pardulum; and, on comparing the extent and ticles of which mutually repelled each duration of these oscillations with those other, and would be atiracted by other of the pendulum, we obtain the produce bodies. But Mr. Cavendish went further of their causes, that is, of the attrac- than Epinus, by supposing that, if this tive power of the masses of lead, and of action is exerted in a less degree chan that of the whole terrestrial globe. But the inverse of the cube from the distance, we can only give a rough sketch of the we n ay prove, by means of the theorem apparatus, and of the cautions and cal. of Newton, on the attraction of a sphere, culatious which the experiment required. that all the electric matter of a body of The moveable power of the lever was this form inust be on its surface.* such, that the least difference of heat be. It is known that our colleague, the late tween the two balls, or only between the M. Coulomb, has since shown, by direct different parts of the air, occasioned a experiments, that the action of electric current that was sufficient to make it vie city is exerted in the inverse ratio of the brate. It was even necessary to find the square of the distance; and lie bas prored degree of attraction of the sides of the in a much more general banner, ibe newooden box in which it was contained cessity of this distribution on the surface and the care in measuring the extent of of bodies, whatever may be their figure. the vibrations, and even to observe When Walsa announced the analogy them without altering them by approach. between the shock given by the torpedo, ing too bear, was inconceivable. All and that of the Leyden phial, it was ob these difficulties did not occur till the jecied that this first did not produce performance of the experiments, and the sparks. Mr. Cavendish, however, set delicate means which were used to over- about explaining the difference. He come them, the necessity of which had constructed, on the principles of his cxe not been foreseen, even by Jir, Mitchell, planation, a kind of artiócial torpedo, belong entirely to Mr. Cavendish. The which presented the same phenomena result was singular. The mean density on being electrified. The real cause of of the globe must be almost five times animal electricity, nevertheless, did not and a half greater than that of water. occur to him; and it remaineri for Volta From this discovery it results, that not to discover an apparatus for continually only the globe has no vacuum, but that producing this wonderful fluid, and in. the substances in its interior must be cessantly to electrify of its own accord: heavier than those on its surface; for the an apparatus, very probably, sinilar, in stones of which common rocks consist its essential points, to those with which are not more than about three, or sel nature has supplied electric fish. dom four, times heavier than water; and It is also hown that the same Me no known stone is five times as heavy. Walsh observed sparks ennitted from the We may therefore believe that metals electric eel of South America: a fish abound most towards the centre of the which possesses this property in a much globe. Thus has this simple experiment given entirely new ideay respecting the Phil. Trans. 1771, p. 584. theory of the earth.

+ Phil. Trans, 1776, p. 196.

greater

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