120 



Messrs. F. C. Calvert and R. Johnsou on the 



of its weight of copper, is, notwithstanding, nearly as hard as iron. 

 This remarkable influence of copper in the bronze alloys is also 

 visible in those composed of 



Sn Cu'^, containing 88-97 of copper. 

 SnCu^o, „ 91-49 



SnCu^s, „ 93-17 



Copper acquires such an increased degree of hardness by being 

 alloyed with tin or zinc, that we thought it interesting to ascertain 

 if alloys composed of these two metals would also have a greater 

 degree of hardness than that indicated by theory : we accord- 

 ingly had a series of alloys prepared in equivalent quantities ; and 

 these are the results arrived at : — 



These results show that these metals exert no action oi^ each 

 other, as the numbers indicating the degrees of hardness of their 

 alloys are rather less than those inquired by theory. Our re- 

 searches on the conductibility of heat by the three above series 

 of alloys throw, we believe, some light on the great diflPerence 

 which the alloys of bronze present as compared with those of tin 

 and zinc ; for we have stated above that the latter conduct heat 

 as a mixture of metals would do, and not as the former series, 

 which conduct heat as definite chemical compounds. 



We shall conclude by giving the degrees of hardness of two 

 other series of alloys, viz. those composed of lead and antimony, 

 and lead and tin. In the series of lead and tin, we find that tin 

 also increases the hardness of lead, but not in the same degree 

 as it does that of copper. 



