Analyfis of the Air. tit 
ftrongeft bombs or cannon, and whirl for- 
tifications in the air. 
This fort of mercurial gage, made ufe of 
in Experiment 89, with fome un&uous mat- 
ter, as Treacle, or the like tinged liquor, 
on the Mercury in the tube, to note how 
high it rifes there, might probably be of fer- 
vice, in finding out unfathomable depths of 
the Sea, viz. by fixing this fea gage to fome 
buoyant body which fliould be funk by a 
weight fix'd to it, which weight might by 
an eafy contrivance be detached from the 
buoyant body, as foon as it touched the bot- 
tom of the fea 5 fo that the buoyant body 
and gage would immediately afeend to the 
furface of the water 5 the buoyant body 
ought to be pretty large, and much lighter 
than the water, that by its greater eminence 
above the water it might the better be feen $ 
for 'tis probable that from great depths it 
may rife at a confiderable diftance from th& 
fhip, tho" in a calm. 
For greater accuracy it will be needful, 
firft to try this fea-gage, at feveral different 
depths, down to the greateft depth that a 
line will reach, thereby to difeover, whe- 
ther or how much the fpring of the air is 
difturbed or condenfed, not only by the 
P z great 
