an i trip roved Air-Pump , &c. 44 - 
\ and / , but as thole {lop- cocks muft be turned by means of a 
key adapted to their fquare tops, and in that cafe their friftion 
again ft the caps would unfcrew or tighten them ; therefore a ring 
is put round each cap, which ring is prevented from turning by 
a pin, and is faftened round the cap by means of a fcrew with a 
milled head. Thefe rings are feen in fig. i . of plate II. Each 
of the flop- cocks is perforated with a hole, which goes from one 
fide to the bottom of it. 
The upper part of the piece of communication terminates in 
a ball a, into which the lower and conical extremity b of the 
tube d is adapted by grinding, and is faftened by the cap c. 
1 he tube d is loldered to the part f, which is made fall to the 
upper board of the frame of the machine, and to which the 
plate//, having the rimgg, is fcrewed with a leather between. 
The lower part of the piece np is fcrewed with a leather be- 
tween to the top of the ftrong brafs veftel qrs , and is termi- 
nated as appears in the figure, for a reafon that will be made 
evident in the fequel. The veftel qrs is faftened to the middle 
fhelf of the wooden frame by fcrews j-j ; and it lias a perfora- 
tion at bottom, which is fhut by the fcrew nut t , and ferves to 
let out the oil, which, after working the machine for fome 
time, will be found lodged in the veftel qrs. 
The tube E r is foldercd into the piece D, and likewife into 
the veftel mentioned above, wherein it proceeds till very near 
the top of the veftel, where it opens. 
The pifton of the pump, with its axis GG, is moved up- 
wards and downwards by means of the rock-work, wheel, 
and handle; which parts being clearly {hewn in fig. i. and 2 . 
of plate II. and alfo being nothing new, require no farther 
defcription. 
4 
To 
