232 



Royal Society :- 



that, as for conductibility of heat by bodies, their molecular condi- 

 tion exercises the greatest influence on their expansion. For ex- 

 ample, we have found that the same bar of steel gives, according to 

 its degree of tempering, the following ratios of expansion : — 



The influence of the molecular state of bodies is also clearly illus- 

 trated in the class of compounds or carbonates of lime : — 



Chalk 



Lithographic stone 

 Stalactite 

 Marble . 



Rates of expansion 

 from 0° to 100°. 



19*6 

 45-0 

 67*0 

 71-0 



Influence of Crystallization. 



Crystallization influences the expansion of bodies as it does their 

 power to conduct heat ; thus, the same zinc cast horizontally or ver- 

 tically has not only a different crystallized structure, but also expands 

 in a different ratio. 



We have also examined the ratio of expansion in several series of 

 alloys made in multiple and definite proportions, but shall give here 

 only one series as illustrating our results. 



