58 Onthe Heat produced by Friction or Compression. 
meter. It was 19,2357: we re-melted it, and its specific 
gravity became 19,2240. After having polished it, its spe- 
cific gravity was 19,2390: we then struck it, and its specific 
gravity became 19,2487. 
Piece of silvers 6. anti Oe. As Wis Malo SET 
Piece of re-melted silver..........000000. 10,4465 
Piece of silver strucks,.0ii.5). 0 os Vee cle’t oc ee O94838 
PIBCO\ Ge COPREr). cinmegaytiawis sk 0.0.0.0 01304 5 See 
Piece) On Copper, SUCK gidrs «6.0 + «ses ee 
Piece of copper, struck a second time ...... 8,9081 
If we compare the foregoing experiments, we see that, 
independently of the difference of the specific gravities of 
the metals, gold undergoes in the compression caused by 
the shock a less condensation than silver, and the latter in 
its turn less than copper; and that thé heat extricated is in 
proportion to the change of dimension. But we must 
compare the piece of copper with that of silver and of 
gold, regarding all three in the state in which they are 
when they are reduced into plates, 7. e. when they have 
undergone the pressure of a flatting-mill, because copper 
cannot acquire its greatest dilatation by re-melting, which 
alters its surface. The re-melting, by producing a greater 
state of dilatation, diminishes the tenacity, which was owing 
to the compression of the metal, and it increases at the 
same time the proportion of caloric, which varies with the 
dimensions. 
We struck into moulds some pieces of similar dimension 
to the above ; but the heat extricated was less considerable, 
and the specific gravity received less increase than when the 
pieces struck were at liberty. This was certainly owing to 
the particles in the latter case coming more closely together 
by sliding over one another. 
At the commencement of our experiments we made use 
of copper, and had, as we supposed, clearly ascertained that 
heat was extricated by compression; but, when all circum- 
stances were alike, mstead of heat, we had a production of 
cold. We verified the temperature of all the objects which 
could have any influence, and we found, by employing a very 
accurate thermometer of M. Pictet’s, which we had used 
throughout the experiments, that the stamper of the fly- 
press was nearly half a degree below the temperature of 
the copper: we directed one experiment towards this ob- 
jeet, and we ascertained that the communication of tem- 
perature takes place in a much more rapid manner by means 
of the blow and of compression, than when the bodies are 
simply 
