3^8 fbe Stcft* [Book VII. 



outer end. This pump commonly (lands near the 

 corner of the front of the houfe, and raifes the column 

 of water up to the cittern O, into which it is conducted 

 by a trough. 



O, the jack-head ciftern for fupplying the injection, 

 which is* always kept full by the pump N j it is fixed 

 fo high as to give the jet a fufficient velocity into the 

 cylinder when the cock is opened. This ciftern has a 

 pipe on -the oppofite fide for conveying away the fur 

 perfluous water. 



P P, the injection-pipe, of three or four inches dia- 

 meter, which turns up in a curve at the lower end, 

 and enters the cylinder bottom ; it has a thin plate of 

 iron upon the end a, with three or four adjutage holes 

 in it, to prevent the jet of cold water of the jack- head 

 ciftern from flying up againft the pifton, and yet to 

 condenfe the fleam each ftroke, when the injection- 

 cock is open. 



* <?, a valve upon the upper end of the injection-pipe 

 within the ciftern, which is fhut when the engine is 

 riot working, to prevent any wafte of die water. 



/, a fmall pipe which branches off from the injection- 

 pipe, and has a fmall cock to fupply the pifton with a 

 little water to keep it air-tight. 



Q^the working plug, fufpended by a chain to the 

 arch g, of the working beam. It is ufually a heavy 

 piece of timber, with a nit vertically down its middle, 

 and holes bored horizontally through it, to receive pins 

 for the purpofe of opening and (hutting the injection 

 and ileam cocks, ^s it afcends and defcends by the 

 motion of the working beam. 



h, the handle of the fteam-cock or regulator. It is 

 fixed to the regulator by a fpindle which comes up 

 through the top of the receiver. The regulator is a 

 circular plftt? 9t" brafs or ca ^ i ron > which is moved 



horizontally 



