342 APPENDIX. 
Sea, the Catch may then by means of a 
Spring, let go its hold ; whereby the Buoy 
will be at Liberty to carry the Machine up to 
the Surface of the Water. 
1 8. The Weight of the finking Ballafl: 
ought to be fo proportioned, as to be juft 
fufficienc to fink the Machine at firft, for as 
the Machine defeends it grows continually 
fpecifically heavier, by reafon of the Conden- 
fation of the Air in its Cavity, on which ac- 
count its Motion will be accelerated, as well 
as on account of the inceflant Adion of the 
Power of Gravity upon it, (o that if this gra- 
vitating Power far exceeded the contrary Re- 
nitency of the Buoy, it would ftrike the Bot- 
tom of the Sea with fo great a Force, as 
might endanger the breaking of the Ma- 
chine. 
Ip. It would therefore be advifeable firft 
to let down the Buoy with fomething of equal 
Weight with the Machine, and an Iron Rod 
intervening between the Machine and the 
Buoy, thereby to guefs by the bending or 
not bending of the Rod, with what Degree 
of Force it might ftrike the Bottom of the 
Sea. And if the Force (hould be found to 
be great, I believe it might be advifeable to 
fix 
