146 VOYAGE to MADAGASCAR. 



a vacuum, they have added a parricular 

 pipe which communicates with the cylinder, 

 and to which they have given the name of 

 a condenfer : it is through this part that the 

 cold water is inje£ted. In order, alfo, to 

 facilitate the redu€tion of the fleam, at the 

 moment of injeiftion, they have added 

 a fraall pump, which is dellined folely for 

 caufing a vacuum in the condenfer. A very 

 fail pie and well-known piece of machinery 

 ferves to regulate the fteam-engme^ and to 

 give it ^ circular motion. For this purpofe 

 a heavy wheel, of a large diameter, is em- 

 ployed, which communicates with the pi ft on 

 of the engine, by means of bent levers, like 

 thofe ufed for turning a fpinning- wheel by 

 the foot. In common engines, the wheels 

 which ferves as a regulator, ought to be 

 twenty feet in diameter, and to weigh from 

 two to two and a half tons. The greater 



part 



