IN ROLLED COPPER BY HAMMERING^ ETC. 247 



degree of Fahrenheit; an increase of heat of 78 degrees 

 would expand the copper about -^-q. This increase of heat 

 I ascertained to be produced. If there be not a connexion 

 between the heat produced and the decrease of density I 

 can conceive no cause. But to attribute it to this cause 

 would presuppose a permanent retention of the expanded 

 statCj of which I know no instance. The particular brittle- 

 ness of hammered copper seems to show that the molecules 

 are in quite a different state to those in annealed copper. 

 It was to draw attention to this singular loss and recovery 

 of density, that I have submitted these few facts to the 

 Society. 



