<2 Mr. Cartwright' 's Patent Steam Engine. 



vacuum ; which, in confequence of the elaftic vapour that 

 feparates from water injected in the ufual mode of conden- 

 fation, no one in the leaft converfant with the philofophy of 

 the fleam engine need be told is impoffible. The con- 

 denfation, in Mr. Cartwright's engine, is performed by the 

 application of cold to the external furface of the vcffel con- 

 taining the fleam. Mr. Cartwright is not, however, the 

 firft who tried this method; the fame has been attempted by 

 feveral; but with fo little fuccefs, that one of our firft 

 engineers in this line has been heard to give it as his opinion, • 

 that, were a pipe to be laid acrofs the Thames, the condenfa- 

 tion' would not be quick enough to work a fleam engine 

 with its full effect. The manner Mr. Cartwright manages 

 this bufinefs is by admitting the fteam between two metal 

 cylinders lying one within the other, and having cold water 

 flowing through the inner one, and enclofmg the outer one. 

 By thefe means a very thin body of fleam is expofed to the 

 greateft poffiblc furface. But this is not all : by means of a 

 valve in the pifton there is a conflant communication at all 

 times between the condenfer and the cylinder, either above 

 or below the pifton, fo that, whether it afcends or defcends, 

 the condenfation is always taking place. 



To reduce the friction of the pifton, which, when frefh 

 packed in the common way, lays a very heavy load upon the 

 engine, Mr. Cartwright makes his folely of metal, and ex- 

 panfive. There is a further advantage in this method, from the 

 faving of time and expence in the packing, and from the pifton 

 Otting more accurately, if poflible, the more it is worked. 



Mr. Cartwright has been equally attentive in Amplifying 

 all the other parts of the engine ; his engine having only 

 two valves, and thofe are as nearly felf-acting as may be. 



But what will probably be efleemed one of the moft im- 

 portant circumftances attending thefe improvements, is the 

 opportunity they afford of fubftituting ardent fpirit, either 

 wholly or in part, in the place of water, for working the 

 engine. For, as the fluid with which it is worked is made to 



circulate 



