524 On Heat & Cold produced by Mechanical 
which was near the open end of the tube, and 
subject to rise or fall by any variation of elas~ 
ticity of the air on either side, being a proper 
manometer: then doubled the density of the 
air in the receiver, and opening the stop-cock, 
the mercurial column soon ran up to its former 
station, but instantly turning the cock again, the 
mercurial column returned or fell down gra- 
dually for 5 or 10 seconds, to the amount of 
neatly , of the whole aérial column, and 
then became stationary. Again opening the 
cock, a quantity of air rushed out, and the mer- 
cury resumed its original station. These effects 
were always the same, on a repetition of the 
experiment. 
EXPERIMENT 11. 
Let the mercurial column of the manometer 
down by a wire tot of the length of the tube 
from the sealed end; then exhausted 3 of the 
_air from the receiver, which was seen by the 
mercury rising to the top of the tube; and upon’ 
opening the cock the mercury fell to its former 
station, but then suddenly turning the cock, the 
mercury gradually rose for the space of 5 or 10 
seconds to more than 4, of its original height 
above the stationary point, and remained there 
till the cock was opened; after which it resum- 
ed its proper station, 
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