APPENDIX. 341 
nefs at great Depths, and in what Proportion 
at different known Depths, and in different 
lengths of time, that an Allowance may ac- 
cordingly be made for it at unfathomable 
Depths. 
16. And becaufe it is probable that the 
Temper of the Air, when the Experiment is 
made, will be either warmer or colder, than 
that of the Sea at a confiderable Depth, it 
will therefore be advifeable to let down the 
Inftrument with a Line to a good Depth, 
there to continue for fome time, till the Air 
in it may be fuppofed to come to the fame 
Temper with the Sea Water : Then the Ma- 
chine is to be pulled up fo far above Water^ 
as to let the Air freely pafs either in or out 
of the Globe and Tube, according as the in- 
cluded Air (hall either have dilated or con- 
traded. Then inffantly let the Machine 
loofe to drop down to the Bottom of the Sea ; 
Which it will do by means of a finking 
Weight of Ballaff, which muff be fixed in the 
following manner, viz. 
17. The finking Weight of Ballaff: muff: 
be fo fixed to the Machine, by means of a 
Catch-Hook, that as foon as the Weight 
touches the Ground at the Bottom of the 
Z 3 Sea^ 
