20 6 Anahfis of the Air. 



ftrongeft veiTels ; and from the vaft cxplofive 

 force with which the air generated from 

 nitre in the firing of gun-powder, will bud} 

 afunder the ftrongeft bombs or cannon, and 

 whirl fortifications into the air. 



This fort of mercurial gage, made ufe of 

 in Experiment §9, 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, vis& 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 of the Tea,- fo that the buoyant body 

 and gage would immediately afcend 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.; 

 Por 'tis probable that from great depths it 

 may rife at a confiderable diftance from the 

 {hip, tho' in a calm. 



Tor greater accuracy it will be needful, 

 fir ft to try this fea-gage, at fcveral different 



depths 



