244 MR. CHARLES o'nEILL ON CHANGES OE DENSITY 



First Series. 

 I had ten pieces of copper cut from different parts of 

 tlie same sheet, which was represented as being best rolled 

 copper. The thickness was about x\ inch, and the pieces 

 weighed from 252 to 320 grains, each being rather more 

 than an inch square. I cleaned them with dilute nitric 

 acid and brickdust, so as to get a clean surface, and then 

 took the density of each piece by a balance which would 

 indicate clearly the lOO^A of a grain, and all the weigh- 

 ings were made to that fineness. I obtained as follows : 

 No. 



I .. 



.... 8-884 



No. 6 



8-881 



2 . 



.... 8-885 



7 



8-88o 



.1 ■ 



.... 8-884 



8 



8-872 



4 ■ 



.... 8-875 



9 



8-870 



5 ■ 



.... 8-884 



10 



8-874 





Mean density . 





8-879 



The pieces were then separately hammered in the 

 genou, each receiving about fifty blows ; the blows passed 

 through about x\ inch, and the pieces being at liberty to 

 extend, they did extend perhaps one-half, but without any 

 cracks or fissures. They were perceptibly warmed by the 

 hammering, though the massive cast iron bed did not 

 allow them to get very hot. After the hammering they 

 were carefully cleaned, and their density again ascertained 

 with the following results : 



No. I 8-850 No. 6 8-866 



2 8-856. 7 8-855 



3 8-851 8 8854 



4 8-856 9 8-855 



5 8-848 10 8-863 



Mean density 8-855 



Loss on density 0-024 



- The pieces were now annealed by putting them in red 

 hot sand, and letting them cool slowly. They were then 

 cleaned carefully and their density taken as follows : 



No. I 8-882 No. 6 



2 8-885 7 



3 8-883 8 



4 8-882 9 



5 8-883 10 8S85 



Mean density 8-884 



