338 APPENDIX. 
have dcfcended 6 ^ 6 y Feet, that is, a Mile 
and a Quarter, and a hundred and thirty two 
Feet. 
1 1. Suppofe again the Machine to have 
defeended to the Depth of three hundred 
and ninety nine Columns, then the Air will 
be comprefl'ed within ^^th part of the 
whole, that is, nearly within one Inch and 
Qiiarter of the Top of the Tube; in this 
Cafe the Machine will have defeended two 
Miles and half, wanting fifty three Feet 5 
which may probably be the greatefl: Depth 
of the Sea. 
12. But if there were occafion to explore 
greater Depths than this, it might we fee be 
done with tolerable Accuracy, by enlarging 
the Capacity of the globofc Veffel, which 
plight be done without making it very cum- 
brous. For fuppofe the Diameter of the Tube 
w^ere about ^ths of an Inch, viz. common 
Musket Barrel bore, and that it were fifty 
Inches long, if the globofe Veffel were nine- 
teen times as big, it would not in that cafe 
exceed the Bulk of three Gallons. But the 
bigger the globofe Veffel, the greater care 
niuft be taken to fecure well the Screw where 
It 
