[ 334 I 



the fpace under or above the piflon, to the contrary ; from 

 which efFedl of this pipe, I call it the circulating pipe. 



The other pipe or dudl is reprefented at c d, fig;. 2, which 

 exhibits a back view of the pump : its extremity c, enters 

 the b'ock of metal V, to communicate with the dudl there- 

 in, and fo with that through the cock into the barrel : its 

 end c has a wing foldered to it, by which it is firmly 

 fcrewed to the piece V, this being necefTary, left the cement, 

 by which alone the joint there is made air-faft, fliould be 

 cracked by any fhock moving the barrel ; or it might perhaps 

 be fecured by the fcrew with only leather interpofed ; this du(5l 

 is a very wide one, that the air n:iay the fooner pafs through 

 it; it has a turn at right angles at d, and another at e, from 

 whence it extends under the pillar B, and pump-plate C D, 

 through the middle of which it rifcs at A ; it has a branch 

 turning at right angles froiu A, under the pump-plate, the 

 end of which terminates in a round orifice with an infide 

 fcrew, that by means of a pipe, furniO.ed with a ftop-cock, or 

 otherwife, another pump-plate and receiver, or feveral of them, 

 may be connedled with it, being laid on the fame table which 

 fupports the pump : when fuch are not ufed, the orifice is 

 clofed with a ftop-fcrew as at D. From' this pipe rifcs a 

 branch E, inferted into the top of the brafs cap F of the glafs 

 veflel Y, and opening into the veflel by a dud made in the 

 thick plate of the cap. G, is a reduced barometer tube to be 



filled 



