[ 262 ] 
Millionth parts. Specific gravity. 
Compreffion of fpirit of wine 66 — 846 
Oil of olives 48 — 918 
Rain-water - 46 — 1000 
Sea- water - - 40 — 1028 1 
Mercury - - 3 — 13595 
Thefe fluids are^not only compreffible, but aifo 
eiaftic : for if the weight by which they are naturally 
compreffed be diminifhed, they expand; and if that by 
which they are compreffed in the condenfer be re- 
moved, they take up the fame room as at firft. That 
this does not arife from the elafficity of any air the 
fluids contain, is evident ; becaufe their expanfion, 
by removing the weight of the atmofphere, is not 
greater than their compreffion by an equal additional 
weight : whereas air will expand twice as much by 
removing half the weight of the atmofphere, as it 
will be compreffed by adding the whole weight of 
the atmofphere. 
It may aifo be worth obferving, that the compref- 
fions of thefe fluids, by the fame weight, are not in 
the inverfe ratio of their denfities or fpecific gravities, 
as might be fuppofed. The compreffion of fpirit of 
wine, for inftance, being compared with that of 
rain-water, is greater than in this proportion, and the 
compreffion of lea-water is lefs. 
The weight of 324 feet of fea- water is equal to 
the mean weight of the atmofphere : and, as far as 
trial has yet been made, every additional weight equal 
to that of the atmofphere, compreffes a quantity of 
fea- water 40 millionth parts; now if this conflantly 
holds, the fea, where it is two miles deep, is com- 
preffed by its own weight 69 feet 2 inches ; and the 
water at the bottom is compreffed 1 3 parts in icoo. 
XLVI 1 I. Conafi 
