134 



MATHEMATICAL AND PHYSICAL SCIENCE. 



[Diss. VI. 



(605.) 

 Lavoisier. 



(606.) 

 His contri- 

 butions to 

 heat and 

 chemistry. 



A man indifferent to external relations pursues even 

 his studies at a disadvantage; and the patient la- 

 bours of so long a life devoted to a single object, 

 would perhaps have told to greater effect had he 

 published the results more frequently, and had he 

 communicated more freely with those qualified to in- 

 terchange their views with his. His excellent mathe- 

 matical education, and his unusual skill in experi- 

 ment, combined with a habit independent of either, 

 but not less valuable, of patiently drawing inferences, 

 might have placed him in the first rank as a discoverer 

 in Heat, in Electricity, or in Optics, 1 each of which 

 sciences was so soon to take a surprising step in ad- 

 vance. In several of his important researches, he 

 was more or less anticipated ; a circumstance which 

 his cold nature would perhaps scarcely have allowed 

 him to make an effort to prevent. Black preceded 

 him in most of his excellent experiments on heat ; 

 JEpinus in his theory of Electricity ; Watt was at least 

 close on his traces in suspecting that water consists 

 of oxygen and hydrogen ; and the admirable experi- 

 ment on gravitation had been devised by his friend 

 Micbell, and was not improbably recalled to his re- 

 collection, by the happy use of the torsion balance 

 by Coulomb. It is given but to a few to achieve great 

 discoveries, nor is the longest life always the most 

 productive. Cavendish had his share, and some of 

 the most considerable of these were even made later 

 in life than is usual amongst experimentalists. 2 It 

 is no mean eulogy of him to say, that the purity and 

 ardour of his pursuit of truth were never exceeded, 

 and that had he been more ambitious of praise, he 

 might have stood as pre-eminent in mathematical 

 physics as he did in chemistry. 



ANTOINE LAURENT LAVOISIER stands in intimate 

 connection with Cavendish, as well by the nature of 

 his pursuits generally, as by the brilliancy and im- 

 portance of his chemical discoveries, which were 

 nearly contemporaneous with those of Cavendish. 

 He was born in 1745, and suffered by the guillotine 

 on the 8th May 1794, without even the shadow of 

 a misdemeanour. He was attached to the sciences 

 of Heat and Chemistry, which he prosecuted with 

 admirable success. He happily availed himself of 

 the discoveries of Black, Priestley, and Cavendish, as 

 well as his own, to establish the important chemical 

 theory which has immortalized him. It is to be re- 

 gretted that he was not always just in citing the 

 English writers from whom he so freely borrowed. 

 Such looseness was, however, common at that period, 

 and (unfortunately) has continued to be so in France 

 even to our own time. 



Lavoisier's more important papers may be classed 

 under two heads ; those referring more immediately 

 to the subject of Heat as a branch of physics ; and 

 those of a more strictly chemical character, princi- 

 pally in support of the " Oxygen-Theory," and con- 



sequently also intimately connected with the doctrine 

 of heat considered in reference to its most ordinary 

 source, Combustion. 



He published in 1772 a paper on the Latent Heat (507.) 

 of Water, and some years afterwards one on the Latent Papers on 

 Heat of Steam, which, in general, merely reproduce h . eat cal<1 

 the views of Black. In the memoirs of the Aca- g p c j fic ~~ 

 demy of Sciences for 1780 (published 1784), we heat, 

 find an important paper on Heat written in conjunc- 

 tion with Laplace, in which the calorimeter is de- 

 scribed, though not under that appellation, together 

 with its applications and their results. The prin- 

 ciple of the calorimeter is too well known to require 

 to be detailed here; but the authors of the joint 

 memoir refer, with commendable precision, to the pre- 

 vious labours of Wilcke of Sweden, who first employed 

 the melting of snow to measure the quantities of heat 

 given off by bodies in cooling. To Laplace and La- 

 voisier, is, however, due an important addition which 

 could alone impart any value to the results, that of 

 the external chamber of ice which prevents fusion 

 taking place by the contact of the external air and 

 by radiation. The French philosophers were not so 

 successful in eliminating the oth^r source of inac- 

 curacy specified by Wilcke, which arises from the 

 difficulty of drawing off the whole of the melted 

 water. Sir John Herschel has of late years proposed 

 what seems to be an important improvement on the 

 calorimeter, by filling the interstices of the snow or 

 ice with water, and estimating the quantity of the 

 former melted by the contraction of volume of the 

 compound mass. I am not aware that it has been 

 as yet practised. I have stated in Art. (88) one ground 

 on which the idea of the calorimeter (so far as not 

 anticipated by Wilcke), may be probably ascribed to 

 Laplace. Another is to be found in the fact that, 

 in the opening of the description of the method in 

 the paper which we are considering, Laplace writes 

 of himself in the first person. 



Of the memorable revolution which Lavoisier in- (608.) 

 troduced into chemistry, more immediately in con- Chemical 

 nection with the subject of combustion, I cannot be the< ""7 of 



, .' , . combina- 



expected to speak here at length. It is well known tion and 

 that the early chemists entertained more correct oxidation, 

 views as to the calcination of metals than those pre- 

 valent during the greater part of the eighteenth cen- 

 tury under the influence of Stahl's theory of Phlo- 

 giston ; and that Lavoisier, in the first instance, only 

 led chemists back into the right road by insisting 

 that the increase of weight observed when metals are 

 calcined in air, must be due to some ponderable sub- 

 stance associated with the metal and derived from the 

 air, and not to the escape of an imaginary spirituous 

 substance, endued with positive levity, and termed 

 Phlogiston. But it required the progress which had 

 already been made in pneumatic chemistry by Black 

 and Priestley, and especially the discovery of oxygen 



1 This last subject seems to have been comparatively indifferent to him. 



2 His discovery of the composition of water was made when he was about fifty years of age. 



