in various Substances. 447 



The raw silk was very fine, and was very equally dis- 

 tributed through the space it occupied, and it formed a 

 warm covering. 



The ravelings of taffety were also fine, but not so 

 fine as the raw silk, and of course the interstices be- 

 tween its threads were greater, and it was less warm ; 

 but the cuttings of sewing-silk were very coarse, and 

 consequently it was very unequally distributed in the 

 space in which it was confined ; and it made a very bad 

 covering for confining Heat. 



It is clear from the results of the five last experi- 

 ments, that the air which occupies the interstices of 

 bodies, made use of for covering, acts a very important 

 part in the operation of confining Heat; yet I shall 

 postpone the examination of that circumstance till I 

 shall have given an account of several other experi- 

 ments, which, I think, will throw still more light upon 

 that subject. 



But, before I go any further, I will give an account 

 of three experiments, which I made, or, rather, the same 

 experiment which I repeated three times the same day, 

 in order to see how far they may be depended on, as 

 being regular in their results. 



The glass globe of the passage-thermometer being 

 filled with 1 6 grains of cotton-wool, the instrument was 

 heated and cooled three times successively, when the 

 times of cooling were observed as follows : 



