Prof. Regnault on the Specific Heat of some Simple Bodies. 117 



pounds of silicon ; and the chemical and crystallographical ana- 

 logies which have been sought to be established between these 

 compounds and other similar compounds whose formula? are 

 definitely known, are by no means certain. Hence it becomes 

 interesting to determine the specific heat of silicon j and during 

 the last few years I have neglected no opportunity of doing so. 



I worked on two varieties of silicon ; crystallized silicon, pre- 

 pared by M. St. -Claire Deville's method, and the same silicon 

 melted at a very high temperature. 



First specimen of crystallized silicon lent by M. Deville; it 

 was in small lustrous crystals, from which the uncrystallized 

 part had been separated as completely as possible : — 



M . 



. . 44^-11 



41& r -06 



38s r -74 



P • 



. . 2^027 



2^-027 



2^-027 



T . 



. 97°-83 



97°-70 



97°-83 



ff . 



. 21°-02 



19°-34 



19°-31 



Aff . 



. . l°-5356 



l°-5032 



l°-4359 



A . 



. . 466^-69 



4668*69 



466s r 69 



C . 



. 0-1655 



0-1686 



01679 



Mean .... 0-1673. 



Second specimen of crystallized silicon lent by M. Rousseau; 

 it had been prepared by M. St. -Claire Deville' s method, and the 

 best-defined and most lustrous crystals were selected : — 



M 



P 



T 



& 



A& 



A 



C 



33& r -38 



2^-027 

 97°-50 

 14°-95 

 1°-4991 

 434^-58 

 0-1757 



34^08 



2? r 027 

 97°-50 

 15°-65 

 1°-5161 

 434^-58 

 0-1767 



Mean 



. 0-1762. 



Third specimen of crystallized silicon from another prepara- 

 tion, which M. Rousseau made by the same method : — 



M 



P 

 T 



e 



AS' 



A 



C 



44^-53 



2^-027 

 99°-67 

 12°-85 

 1°-9714 

 422s r -96 

 0-1712 



Mean . . 



42^-515 

 2^-027 



99°-77 



13°- 70 

 l°-9275 

 422s r -96 

 0-1751 



. 0-1742. 



43^-815 

 2& r -027 

 99°-82 

 ll°-37 

 2°-0017 

 422^-96 

 0-1722 



Lastly, Captain Caron lent me a large quantity of crystallized 

 silicon, remarkable for its lustre and the distinctness of its crv- 



