BY IIEAT OF METALS AND ALLOYS. 



877 



foiming them is not surprising, as in all probability there exist chemical combinations 

 between the two metals,— just as it may be said that the specific gravity of an alloy ik 

 approximately equal to the mean specific gravities of the volumes of tlie component metals, 

 so also from the foregoing we may deduce that the volume which an alloy mil occupy 

 at any temperature between 0° and 100° is approximately eqml to the mean of the com- 

 ponent volumes of the metals at the same temperature, or, in other words, the cubical or 

 linear coefficients of expansion, by heat of an alloy between 0° and 100° are approximately 

 equal to the mean cubical or linear coefficients of expansion by heat of the cwnponenf 

 metals. 



In Table XII. I have given the values from Table X., together with the observed and 

 calculated specific gravities and conducting-powers of the alloys experimented with. 



The specific gravities of some of the alloys are not given, as they were not determined 

 with the others. Their values deduced, with the help of the data given in this paper, 

 would not be correct, as for the present research the castings were made more with the 

 idea of producing a perfect surface than an absolute solid ; no doubt many of them had 



MDCCCLXVI. 6 c 



