f 4 2 5 ] 
GI is the fiphon-gage j which fcrews on and off, 
and is adapted to common purpofes. It confifts 
of a glafs tube hermetically fealed at c , and fur- 
nifhed with quickfilver in each leg $ which, before 
the pump begins to work, lies level in the line 
a b ; the fpace be being filled with air of the com- 
mon denfity. When the pump exhaufts, the air 
in be expands, and the quickfilver in the oppofite 
leg rifes, till it becomes a counter-balance to it. 
Its rife is fhewn upon the fcale le , by which the 
expanhon of the air in the receiver may be nearly 
judged of. When the pump condenfes, the quick- 
filver rifes in the other leg, and the degree may be 
nearly judged of by the contraction of the air in 
be : marks being placed at ~ and of the length 
of be from c ; which fliews when the receiver con- 
tains double or treble its common quantity. 
KL is a ferew-frame to hold down the receiver, in 
condenfing experiments, which takes off at plea- 
fure ; and is fufficient to hold down a receiver, 
the diameter of whofe bafe is 7 inches, when 
charged with a treble atmofphere : in which cafe 
it aCts with a force of about 1200 pounds againft 
the ferew-frame. 
M is a ferew, that fatten s a bolt, which Hides up 
and down in that leg, by means whereof the ma- 
chine is made to ttand fall on uneven ground. 
Fig. II. 
Is a perpendicular feCtion of the barrel and cock, 
&c. where 
AB reprefents the barrel. 
H h h 
CD 
