354 Dr. Calvert and Mr, R. Johnson on the 



of conical. In this case there would be such an enormous amount 

 of friction to be overcome before such a phiff could be forced out, 

 that we cannot draw any inference from the formula. There 

 would indeed be friction in eveiy case where /8 is less than a, and 

 therefore the result stated in paragraph 18 is the only one to 

 which the calculation leads. j j^^ Pratt. 



Calcutta, August 22, 1859. 



LV. On the Specific Gi'avities of Alloys. By F. Grace 

 Calvert, Ph.D., F.R.S., F.C.S. ; and Richard Johnson, 

 F.C.S. i^-c.^ 



THE study of alloys and amalgams having been made espe- 

 cially with impure or commercial metals, the results ob- 

 tained have been such that it has been impossible to solve the 

 important question. Are alloys and amalgams chemical mixtures 

 or compounds ? It is with the hope of throwing some light on 

 this subject that we have for the last two years been engaged in 

 examining comparatively some of the physical properties, such as 

 the conductibility of heat, tenacity, hardness, and expansion of 

 alloys and amalgams made with pure metals, and in multiple and 

 equivalent quantities, as follows : — 



1 Copper and 1 Tin. 

 1 „ and 2 „ 

 1 „ and 3 „ 

 1 „ and 4 „ 

 1 „ and 5 „ 

 and 



1 Tin and 2 Copper. 

 1 „ and 3 „ 

 1 „ and 4 „ 

 1 „ and 5 „ 



By this method we have succeeded in ascertaining, first, the 

 influence which each additional equivalent quantity of a metal 

 exerts on another ; secondly, the alloys which are compounds and 

 those which are simple mixtures ; for compounds have special 

 and characteristic properties, whilst mixtures participate in the 

 properties of the bodies composing them. This method of in- 

 vestigating alloys and amalgams has enabled us to ascertain 

 which metals combine together to form definite compounds, and 

 those which, when melted together, only form mixtures. Thus, 

 for example, bronze alloys are definite compounds, for each alloy 



* Communicated by the Authors. 



