116 MR. F. C. CALVERT AND MR. R. JOHNSON 
This table exhibits a curious fact, viz., the high degree 
of hardness of cast iron as compared with that of all other 
metals, and although we found alloys which possessed an 
extraordinary degree of hardness, still none were equal to 
cast iron. 
The first series of alloys we shall give is that of copper 
and zine. 
Obtained | Calculated* 
Formule of Alloys and per centages. eet eet eos ores ae 
/ lbs. hs 
ZiOagitiy ter be Ww kss..d 2050 | 427-08 | 28083 
bad te aie. fd 2250 | 46875 | 276-82 
Pant geen ker 2250 | 468-75 | 276-04 
LAC pyc ae 2270 | 472-92 | 261-04 
Zn Cu a sos} ae (eae 2900 | 60417 | 24333 
Cu Zn, Va pat seseaeeeees| Broke with 1500 Ibs. without 
Cu 2464. the point entering. 
Cu Zn, vo 75.36 Marere ty 95 8 Broke with 1500 lbs. with an 
Pan ipees impression $ mm. deep. 
Cu Zn, ics 80°43 se dele ine Entered a little more than the 
Cu 16:30 ) above; broke with 2000 lbs. 
Cu Zn; \Zn asin SPR: Entered 2 mm. with 1500 lbs.; 
B ) broke with 1700 Ibs. 
These results show that all the alloys containing an 
excess of copper are much harder than the metals com- 
posing them, and what is not less interesting, that the 
increased degree of hardness is due to the zinc, the softer 
metal of the two which compose these alloys. ‘The quan- 
tity of this metal must, however, not exceed 50 per cent. of 
the alloy, or the alloy becomes so brittle that it breaks as 
the steel point penetrates. We believe that some of these 
alloys, with an excess of zinc, and which are not found in 
commerce owing to their white appearance, deserve the 
* To calculate the hardness of an alloy we multiplied the per centage 
quantity of each metal by the respective hardness of that metal, added the 
two results together, and divided by 100. The quotient is the theoretical 
hardness. 
