. 5h J 
ing-a flat flider.at the orifice OF 
fhe tube, which, being puthed in 
when the tube and the focket-are 
full of .air, cuts off exactly the cos 
lunmn of dir Within the tube, and 
at once fhuts out that quantity of 
air which is. more than the three 
inches wanted. All that part of 
the column of air which is thus cut 
oit by the flat flider, is let out by 
een ing. or ines ORS the whole 
be tak ‘Ke oe whales 
change may afterwards happen to 
the €xpanfive force, or to the elaf+ 
ticity cat the air within this mea 
GUE DS > ; 
ADbE Fontan ufes thig Pudiomé= 
» 
