212 



A P P E N D I X. 



" confuQiption of water in the boiler is very inconfider- 





(( 



able, . in comparifon to what would happen if the 

 compreffion arifing from the throat-pipe and valve of 

 *' that machine was taken off, and the prcflure of the 

 atmofphere only admitted. But by the reilraint of that 

 *' valve, the vapour becomes hotter, and increafes in 

 " rarity and elafticity ; qualities eflential to the purpofes 

 " of the engine, although tjie reverfe of thofe which 

 " oun-ht to take place in common diftillation. For the 

 " columns of vapour Hiould be rcniovcd from the boiling 

 " fluid as fafl: as they afcend, without luftering any other 

 " refiftance than that- of the atmofphere, which, in the 

 " ordinary bufinefs of diftillation, cannot be prevented, 



*' The impropriety of the common procefs of diftillation, 

 will appear evident by comparing it with the above 

 principles and fd&s. 



It 





" In the common method of diftillation, the whole 

 " column of vapour from a ftill ot v^'hatever iize, after 

 afcending to the ftill-head, mufl: not only find its paffage 

 through a pipe of fcarce an inch and half diameter ; but 

 " defceud contrary to its fpecific gravity through air 

 " which is fifteen times its weight, in fpiral convolutions: 

 " a courfe fo extremely ill adapted to the progrefs of an 

 *' elaftic vapour, that frequent! v the flill-head is blown off 

 " with incredible violence, owing to the increafcd heat 

 1, '' and 



