(2193) 
drawn fmall with a lamp, aud turned down a little way,after 
theEiannerexpreffedinF/^^ I. This Cylinder was immerfed 
perpendicularly widi the crooked end uppern[ioft ; by which^ 
it funk in the water^the preiTure thereof did gradually force 
in fo much water as thruft out the Air proportionable to every 
depth, till the Cylinder was fo far immers'd, that the hole of 
the Crooked part of it was juft 39 feet under water/ andtheit 
it being drawn up, by meafuring from the bottom of the Cy- 
linder to the height of the hole in the crooked part by a pair 
of Compaffes, the water was found to fill the Cylinder fo near 
the half, that^the motion of the fuperfice of the water3(whtch 
then was very fmooth) and the minutenefsof the difference 
being confider'd, it was thought fit to ftate it to jufthalf 3 ac- 
cording to whichjConfirm'd by the Trials at other depths^ the 
enfuing table was computed. 
The Proportion of theJF<?f^^if of Salt- water to that of Frefii, 
was found by weighing fome Ounces of both in a bottle \^here- 
of the weight was exactly known, and which was made with fo 
fmall a neck, that the addition or diminution of one fingle 
drop in it was difcernible^ 
The Table is on thefe grounds computed upon the fupposM 
Perpendicular immerfion of a Cylinder of 60 inches, clofe at 
one end,and having the open end downwards* The firjl Co- 
lumn ftiews the feveral depths in Feet and parts of Feet. The 
fecondy in half Fathoms and whole Fathoms > a Fathom be- 
ing fix Englifh feet* The third, the proportionable parts of 
Compreflion of any Quantity of Air at the feveral depths in 
tbefirft 2 Columns. The /b«r^^ hath thefe proportions to a Cy- 
linder of 60 inches,expreft in Inches and parts of Inches.-which 
may eafily be further calculated to any other depth defired. 
And that thefe Trials may not be thought to have been 
made out of meer Curioficy, they will^by confidering and pra- 
ctical men^be found Ufeful for thofe, who have occafion to 
dive for recovering things loft in water, forafmuch as by thofe 
Experiment? they may afore hand know, to what depth they 
may^when they fink in the Diving Bell or other fit Inftrumcnrs, 
endure the Compreflion of the Air for refpiration^as alfojhow 
they may furnifli themfelves with Air in a fit vefTel for fupplv* 
Ggga The 
