Specific Gravities of Alloys. 355 



has a special conductibility of heat. Thus the alloy 



The same fact is also observed in the expansion or contraction 

 of these alloys. Whilst, on the contrary, the alloys of tin and 

 zinc being mixtures, conduct heat, have a specific gravity, and 

 expand according to theory, or the proportion of tin and zinc which 

 compose each alloy. Thus for heat,— 



Obtained. Calculated*. Difference. 

 ZnSn^ . . . . 15-15 14-90 0-25 



ZnSn .... 16-00 15-80 010 



Zn^Sn .... 16-65 16-95 0-30 



Specific Gravity. 



Obtained. Calculated*. Difference. 

 ZnSn^ . . . . 7-274 7-193 0-081 



ZnSn .... 7-262 7-134 0-128 



Zn^Sn . . . . 7-188 7-060 0-128 



We shall divide our researches on the specific gravity of alloys 

 and amalgams under two heads : first, those which have a higher 

 specific gravity than indicated by theory; and secondly, those 

 which have a less specific gravity, or expand. ■ .■ , a 



I. Alloys which have a higher specific gravity than indicated 

 by theory. Results : — 



* The principle upon wl.ich tlie theoretical conductibility, specific gra- 

 vity, and ixpausion are calculated, is similar to that followed with respect 

 to hardness, for which see page 4 of our pauer " On HarUnes;. 

 2 A 2 



