10 6 Anal^fis of the Air. 
ftrongeft veffcls 5 and from the vaft cxplofive 
force with which the air generated from 
nitre in the firing of gun-powder, will burft 
afunder theftrongeft bombs or cannon, and 
whirl fortifications into the air. 
This fort of mercurial gage,^ made ufe of 
in Experiment 89, with fome unftuous mat- 
ter, as Honey, Treacle, or the like, on the 
Mercury in the tube , to note how high it 
rifes there, might probably be of fervice^ 
in finding out unfathomable depths of the 
Sea, by fixing this fea-gage to fome 
buoyant body which fhould be funk by a 
weight fixt to it, which weight might by 
an eafie contrivance be detached from the 
buoyant body, as foon as it touched the bot- 
tom ofthefea,- fo that the buoyant body 
and gage would immediately afeend to the 
furfacc of the water j 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 fecn ; 
For 'tis probable that from great depths it 
may rife at a confide.rablc diftance from the 
fhip, tho' in a calm. 
For greater accuracy it will be needfuU 
firft to try this fea*gage, at feveral different 
depths, 
