56 ON THE ALLOYS OF COPPER AND ZINC. 
which agrees with those of Karsten,* of Mallet,t and of Guettier.f Calvert and 
Johnson $ have recently attempted to express these differences numerically. The 
alloy containing 54 per cent of copper, which is still so tenacious that small bits 
cannot readily be broken from it, was found to be exceedingly difficult to cut 
with a cold-chisel; for though stil so soft that it could be filed without any 
very great trouble, it destroyed at once the edges of cutting instruments, though 
the latter were well tempered. ‘This peculiarity appears to be connected with the 
fibrous structure of the alloy. 
In conclusion, I must express my gratitude to my friend, Professor J. P. Cooke, 
of Cambridge, who has kindly invited me to make use of the admirable laboratory 
in which this research has been conducted. By his suggestion, moreover, my atten- 
tion was first directed to the subject. Nor can I omit to mention the fact, that I 
am indebted to Messrs. J. Davis, Jr. and John Revere, officers of the Revere Copper 
Company of Boston, for the gratuitous use of the large quantities of metal which I 
have employed. I have also been permitted by them to make free use of the fur- 
naces and other appliances in the extensive founderies of the company. For the 
valuable aid and uniform kindness of these gentlemen, I would here return my 
warmest thanks. 
* Loc. cit., S. 393. 1 Loc. cit, passim. $ Loc. cit., p. 199. 
T Loc. cit, p. 307; also Gmelin's Handbook, (Cavendish Soc. Edit.,) V. 479. 
HARVARD COLLEGE LABORATORY, 
September 1st, 1859. 
