an improved Air-Pump, kz. 44 1 
oi-.lcr to bring down again all thofe parts, and to Unit the valve 
wlien the prefl'ure of the foot is removed, there is an open 
hrafs tube N, fattened to the piece K, which contains a fpiral 
fpruig, that, bearing againft the extremity of the brafs frame 
00, pufhes it downwards. 
This principal mechanitm being difpatched, it will be very 
cafy to deferibe the remaining parts of this excellent machine : 
but before we proceed to that, I fhall briefly deferibe another 
mechanifm, which Mr. Haas has lately contrived, to fupplv 
the place of that juft mentioned, viz. of the lower part of the 
infhument, as being much more limple, and capable of an- 
fwering the fame purpofe. 
A feel ion of this new thought, which he is going to execute 
for another pump, is (hewn in fig. 7. of plate III. 
AB is the lower extremity of the barrel. CCDE is a piece 
of brafs perforated quite through with a large and cylindrical 
hole, and is ferewed to the barrel inflead of the piece K of fig. 
1. with a leather between. O11 one fide of this piece CDE, 
part of the furface is flattened, and to it is adapted, bv means 
of ferews and a leather, the piece of brafs G, to which the 
tube H is foldered, which correfponds to the tube RS of fig. 1. 
The aperture of CC, towards the cavity of the barrel, is co- 
vered by a piece of oil-filk, like that reprefented in fig. 6. 
which is kept flretched by a brafs ring LL, funk into the piece 
CCD. 
Within the cylindrical perforation of the piece CCDE, there 
is a long pifton Kir, conlifling of the following parts. IK is 
its axis, which fpreads at top into a flat plate r, and the lower 
extremity of which is fattened at N to the lever MO, which 
moves round the center M. Towards the middle of the axis, 
there is a piece of brafs, the fhape of which is more eafily 
M m m 2 underflood 
