Hardness of Metals and Alloys. 115 



other is admitted to be the harder of the two bodies experimented 

 upon. Thus, for example, 



Diamond, Iron, 



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 dififerent 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 apparatus 

 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 removing the weight from the end 

 of the longer arm of the lever. The machine consists of a lever, 

 H, with a counterpoise, B, and a plate, C, on which the weights 



arc gradually placed. The fulcrum L bears on a square bar of 

 iron A, passing through supports, E E. The bar A is graduated at 

 a, and has at its end a conical steel point, F, 7 millims. or 275 

 of an inch long, 5 millims. or 01 97 of an inch wide at the base, 



I '> 



