[ i65 ] • 



Now on examination k will be found that there Is fufficient 

 reafon to think that this equality or compenfation took place in 

 every inftance. 



Thus, comparing coaks and charcoal, we muft obferve that, 

 according to Dodor Watfon's experiments, charcoal gains 9 per 

 cent, by expofure to the air for a few days after it is made, by 

 abforbing partly air and partly moifture.— 3 Watfon, p. 43. 

 And, according to Dodor Prieftley, 15 per cent, in a month; and 

 this feems its maximum.—^ Prieft. p. 417- new edit. But coaks 

 gain only 3 per cent.-3 Wats, p. 46. and ftill lefs when well 

 burned. Thefe dedudions being made, it will be found that 

 the abovementioned 6oolbs. of charcoal will be reduced to 510, 

 and the 403lbs. of coak to 391*; the difference then is only 

 1 1 gibs. 



To account for the equality of refults, notwlthftanding this 

 difference, we mufl confider that coal containing afphalt, a much 

 denfer fubftance than any vegetable oil, is never fo thoroughly 

 chared as woods are, as Dodor Watfon has alfo hinted ; fo we 

 have feen that Newcaftle coal is reduced only 72 per cent. 



though 



* Here I mua mention an error of ipipveflion Jn Mr. Lavoifier's Memoires, which 

 may deceive : In the text, p. 386, the quantity of coaks is fa.d to be 552, but in 

 the third table, p. 39'. " is faid to be 4°3 i f° ^'f° i" '^^ ^"^ '1^= quantity of char- 

 coal is faid to be 960, and in the table only 600, though the ,neafures of both are 

 the fame in both pages. However I found the text wrong and the table right. 



