56 On the Heat produced by 
might be produced in the urine of any one animal, by such 
alterations of diet, as its constitution would permit; for as 
far as any inference can be drawn from these varieties, 
which naturally occur, it would appear, that persons sub- 
ject to calculi consisting of uric acid, as well as gouty per- 
sons, in whom there is always a redundance of the same 
matter, have much reason to prefer vegetable diet ; but that 
the preference usually given to fish above other kinds of 
animal food, is probably erroneous. 
IX. On the Heat produced by Friction or Compression, 
By M. Berruo.yuet.* 
Some years ago, with a view of more fully elucidating 
the origin of the heat occasioned by compression and fric- 
tion, I formed the idea of examining by the help of a ily- 
press, the effects of compression on the metals: I applied 
to M. Gengombre for a press belonging to the Mint, and I 
requested Messrs. Pictet and Biot to assist me in my ex- 
periments. These were pursued for some time with ail the 
precision that might be expected from such skilful coadju- 
tors; but they were interrupted and abandoned before being 
brought to the point which I wished: I shall nevertheless 
present the results of some of these experiments. 
I prepared pieces of gold, silver, copper, iron and bronze; 
all of the same dimensions, in order to submit them to the 
action of the press; but the experiments were chiefly made 
with those of silver and copper. 
In order to determine the heat which the pieces of metal 
acquired by the shock of the fly-press, a thermometer 
placed horizontally was at first used; but it was afterwards 
found best to throw the piece of metal into a quantity of 
water sufficient to cover it. We had ascertained by preli- 
minary experiments the relation which exists between the 
heat acquired by a certain weight of water, and the tem- 
perature of a given weight of each metal plunged into it : 
we thus estimated, by means of the heat which the water 
acquired on comparing its weight with that of the metal, © 
the temperature to which the metal had been raised. 
We submitted a piece of metal to the shocks of a fly- 
press put in motion by two men who were accustomed to 
this operation: we determined the heat acquired, and al- 
Jowed the metal to return to a temperature precisely similar to 
* Mem, d’ Arcueil, tom. ii. page 441, F 
Po, that 
