(605.) 
Lavoisier, 
(606.) 
932 
A man indifferent to external relations pursues even 
his studies at a disadvantage; and the patient la- 
bours of so long a life devoted toa 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, 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; 
Z£pinus 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 
Michell, and was not improbably recalled to his re- 
collection, by the happy use of the torsion balance 
by Coulomb. Itis given but toa 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.? It 
is no mean eulogy of him to say, that the purity and 
ardour of his pursuit of truth were neyer 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 
His contri- ynder two heads; those referring more immediately 
butions to 
heat and 
to the subject of Heat as a branch of physics; and 
chemistry, those of a more strictly chemical character, princi- 
pally in support of the «‘ Oxygen-Theory,” and con- 
. f 
MATHEMATICAL ben PHYSICAL SCIENCE. 
“~~ (Diss. VI. 
sequently also intimatély 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 (607.) 
of Water, and some years afterwards one on the Latent Papers on 
Heat of Steam, which, in general, merely reproduce cata 
the views of Black. In the memoirs of the Aca- spec 
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 other 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) oneground 
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- 
troduced into chemistry, more immediately in con- Chemical 
theory of 
; combina- 
It is well known ¢ion and 
that the early chemists entertained more correct oxidation, 
nection with the subject of combustion, I cannot be 
expected to speak here at length. 
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. 
