[ 3-6 ] 



"upward from the proper diredliion, when it is urged forward 

 by the wheel, and yet checked by the pifton rod after the pif- 

 ton is raifed to the top of the barreh To confine the rack 

 in the true Hne of its motion, it is made perfedlly ftraight 

 and of the fame dimenfions in its whole lenjrth, and its cafe 

 the fame, fo as to fit each other mofl cxaftly, that it inay be 

 kept in its due pofition when the greatefl part of it is drawn 

 out of the cafe; for which purpofe alfo it is made, (as like- 

 wife the cafe) fo much long-r at either end than the part 

 necefTary to be toothed, as to permit a great part of it to re- 

 main in the cafe whrn the piflon rod is drawn out to its 

 utmoft extent : accordingly, in this pump, it adls in this refpc(fl 

 as well as could be wiflied *. A notch is cut out of the cafe 

 at I, to allow the teeth of the wheel to take into thofe of 

 the rack ; and to keep the cafe firmly in its place, little notches 

 are cut in the upper edge of it, into which the contiguous 

 parts of the pillars are let, and it is fecured fo by wedges 

 2, 2, underneath. It will be known that the cafe of the 

 rack h:is its due pofition when, the arna G being taken ofF, 

 both the rack and the pii^on rod, pulled out to their limit, 



are 



* By this contrivance of fixing the barrel of the pump horizontal and its rack 

 underneath the barrel, it is ni:.de fo portable that I have picked it (the gage glafs 

 and receiver being taken off) in a box two feet lon^.;, eighteen inches wide and feven 

 in deptli ; and it fliould be remembered, that the moft operofe parts of it here 

 defcribed are the frame; and machinery necciTary to render a pump with fo long a 

 cylinder portable ; a great part of which machinery, if it were not portable, would 

 not be fpared, but merely exchanged for the huge frame of thofe fo conftrudled. 



