1817.] Collet-Descotils. 421 
malady under which he sank. Under the appearance of strength 
and health, he suffered a perpetual uneasiness, which rendered the 
labours of the laboratory very disagreeable, and often insupportable. 
He exhibited an example of the best social and domestic virtues. 
He was devoted to his friends; full of affection for a father who 
has survived him ; occupied continually with the care of his chil- 
dren ; an excellent husband ; the happiness which he enjoyed with 
an admirable wife was noticed by all. Descotils had a very elevated 
character, such as we should like to find in all those who cultivate 
the sciences. He bequeaths to his two sons a name which he has 
honoured by his labours and his noble qualities, and which will long 
Jecal the loss of a distinguished philosopher and an excellent man. 
He died Dec. 6, 1815, of a chronic peritonites, at the age of 42. 
ARTICLE II, 
On the Chemical Phenomena of Heat. By Mr. J. B. Emmett, of 
Trinity College, Cambridge. 
Tue following pages contain. a brief examination of some facts 
relating to the effects of heat. They are the beginning of a series 
of papers on the principles of chemical philosophy. In some of the 
first communications I propose examining these subjects in a popu- 
lar point of view, in order that they may be readily understood and 
applied by those chemists who have not acquired any considerable 
degree of mathematical knowledge; afterwards | shall proceed toa 
more rigorous solution of the various problems, and apply the prin- 
ciples to the phenomena of decomposition, the investigation of the 
laws of affinity, simple and compound; the laws of expansion of 
solids, liquids, and aeriform bodies ;. and the laws of crystallization. 
The subject involves many difficulties; in our progress we shall 
observe many facts which the principles cannot at present explain. 
Let not these, however, condemn the whole ; let us consider them 
as comets, to ascertain whose orbits we are not yet furnished with 
sufficient data. Regular and patient investigation will clear the 
path, and gradually remove these difficulties. The phenomena of 
crystallization will present the most numerous and greatest difficul- 
ties, which will of course come under consideration in due time, 
and be minutely investigated. In the course of these researches I 
have not met with one fact which militates against the principles 
laid down. 
All bodies, whether in the state of solidity, fluidity, or aeriform 
elasticity, are augmented by an increase, and contracted by a dimi- 
nution, of their sensible heat. From these phenomena, it is mani- 
fest that the particles of that which we usually denominate matter 
are acted upon by two powerful antagonist forces—one centripetal, 
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