243 



XVIII. — On Changes of Density which take place in 



Rolled Copper by Hammeri7ig and Annealing. 



By Mr. Charles O'Neill. 



Read March 5th, 1861. 



A GENTLEMAN engaged in the application of copper to a 

 certain purpose in the arts believed that it was possible to 

 compress or condense the best commercial rolled copper 

 so as to increase its density and improve it for the pur- 

 poses he had in view, which I may state were in connexion 

 with engraving or etching upon the metal. He devised or 

 applied a powerful machine for the purpose of testing this 

 idea, by means of which a great power could be brought 

 to bear upon the copper by a succession of blows acting 

 through a regulated space on the principle of the geuou. 

 The results were not satisfactory, and I was applied to in 

 order to ascertain what was the actual increase of density 

 obtained by a moderate amount of hammering. The first 

 experiments I made did not show that there was any in- 

 crease of density, but pointed in the opposite direction, 

 intimating a loss of density. Nobody was inclined to 

 accept this result, but further experiment confirmed it, 

 and then a regular series of experiments was made to test 

 the point, which resulted in a further confirmation of the 

 earlier experiments. It was afterwards found that anneal- 

 ing the hammered pieces of copper increased their density, 

 bringing them almost exactly to the same density they 

 possessed before hammering. I proceed to give details of 

 several of the experiments. 



