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VII. — On the Hardness of Metals and Alloys. 
By F. Cracu Catvert, M.R.A. of Turin, F.C.S. &c.; and 
Ricwarp Jounson, F.C.S., Se. 
Read April 6th, 1858. 
Tue process at present adopted for determining the com- 
parative degree of hardness of bodies consists in rubbing 
one body against another, and that which indents or 
scratches the other is admitted to be the harder of the 
two bodies experimented upon. Thus, for example, 
Diamond, Tron, 
Topaz, Copper, 
Quartz, Tin, 
Steel, Lead. 
This method is not only very unsatisfactory in its 
results, but it is also inapplicable for determining with 
precision the various degrees of hardness of the different 
metals and their alloys. We therefore thought that it 
would be useful and interesting if we were to adopt a 
process which would enable us to represent by numbers 
the comparative degrees of hardness of various metals and 
their alloys. 
To carry out these views we devised the following appa- 
ratus and method of operating. The machine used is on 
the principle of a lever, with this important modification, 
that the piece of metal experimented upon can be relieved 
from the pressure of the weight employed without re- 
moving the weight from the end of the longer arm of the 
VOL, XV. Q 
