518, Mr. PRINCE’s Account sof, 
the hole into which tubes, &c. are occafionally fcrewéd tó per- 
form experiments without removing the plate: the pricked 
line at O fhows the place of the {crew which preífes the plate 
againft the pipe: P Q. the pipe and common gage ftanding in 
front of the pump. SERO 
Fig. 2. is a horizontálfe&tionof the cock and pieces, contain- 
ing the ducts leading from it to the receiver, the cifterns, and 
the valves on the top of the barrels. - A B the du& connecting 
the cifterns together. -C D the du& leading from the cifterns 
to the cock. GH the du& leading from the cock, through 
the pipe A B, (fig. 1.) to the valves. ^ DE the du& through 
the.cock, which occafionally connects the two Jait-mentioned 
ducts with the duct E F, leading from ‘the cock to the receiver. 
I. the du& in the cock leading to the atmof; phere, which, when 
connected with the du& at D, lets the airinto the cifterns and 
barrels for condenfation ; the other duct through the cock at 
the fame time connecting H and E. This du& alfo, when 
connected with E, reftores the equilibrium in the receiver. 
KL is part of the du& leading from the cifterns to the gage. 
The pricked circles fhow the places of the pipe and valve- 
pump on the piece, and 7 the place where the air enters the 
valve-pump from the duct-G H, and is thrown into the atmof-- 
phere, when the pump exhaufts. : i 
Fig. 3. fhows the under furface of the boxes, which contain 
the collars of leathers, with the crofs-piece, whieh connects 
them together, having a du& through it, as reprefented by the 
pricked line, through which the air pafles from the. valves to 
the pipe: this fig. is defigned chiefly to fhow the places in 
which the valves play, as at I. 
š 
Fig. 
