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under furface of the arm being on a level with the upper 

 one of the bar; this arm fupports the gage glafs Y, and ter- 

 minates in a crofs piece (making together the form of the 

 letter T) to which piece and to the arm, the receiver-plate is 

 fcrewed by fcrews underneath, inferted into its thick margin. 



The bar M fupports the upright pieces or pillars o, o, 

 terminating in the femicircular arms p, p, on which the bar- 

 rel is fattened by four fcrews at p, p, fcrewed a little way 

 into its projeding rings. Thefe pillars are made of iron, and 

 very ftrong, being half an inch in thicknefs ; they are alfo 

 moft firmly fixed, and fhould be brazed in the bar which fup- 

 ports them ; this being neceflary, as all the force of the handle 

 of the wheel, by which the rack is worked, bears againft thefe 

 pillars ; and, if they were to be Shaken, the cement by which 

 the receiver pipe is connedled with the pump would be broken 

 which cannot otherwife happen. The pillars fupport alfo the 

 iron cafe or flieath P P, extended underneath the pump barrel, 

 ■Within which cafe Aides the toothed bar or rack F, moved by 

 the wheel, and this rack (with its cafe) is fixed exadlly pa- 

 rallel to the axis of the cylinder, that it may draw out the 

 piflon rod precifely in that diredion in which itfelf moves : 

 the bar is -^V of an inch in thicknefs, but is an inch in 

 breadth from the bottom of its teeth to the back of it. It 

 is made thus firong that the end of it may not be ftralned 



upward 



/ 



