HYDROSTATICS. 
from the following table, taken from the 
observations of Dr. Blagden and Mr. 
Gilpin. 
Decrees cf 
Heat. 
Balk of the Water. 
Specific Gravity. 
30° 
35 
99910 
1.00090 
40 
99070 
1.00094 
v 45 
99914 
1.00086 
50 
99932 
1.00068 
55 
99962 
1.00038 
60 
100000 
1.00000 
65 
100050 
0.99950 
'■ 70 
100106 
0.99894 
75 
100171 
0.99830 
80 
100242 
0.99759 
85 
100320 
0.99681 
90 
100404 
0.99598 
95 
100501 
0.99502 
too 
100602 - 
0.99402 
We must suppose the water of .the Dead 
Sea to be highly impregnated ; since it ap- 
pears to weigh nearly a fourth more than 
common sea water. 
The anomalies lay between 32° and 45°, 
and are accounted tor by the contraction 
which takes place in water about to freeze, 
and its sudden expansion afterwards : by 
this we understand the course of bottles, 
pitchers, &c. being burst when the water 
they contain freezes. The difference in 
bulk between water and liquors in the 
winter, and in the summer season, averages 
about three per cent : hence many great 
dealers have thought it worth their while 
to buy only in tlse former season, when 
the liquors have been most concentrated. 
The specific gravity of a body either 
fluid, or solid, is ordinarily found by means 
of the hydrostatic balance; a most ingeni- 
ous device for exactly ascertaining the 
weight, either immersed in the water, or 
in the air. The construction of this in- 
strument requires peculiar nicety, but it 
may be appended to any common balance; 
as will be understood from the following 
description. Each scale should have a 
small hook fixed to the centre of its bot- 
tom, or lower side ; so these small weights 
may be attached by means of horse-hair, or 
fine silk, thence to suspend a body in water 
without wetting the scale. First weigh the 
body in the usual manner in the scales, 
with great exactness ; immerse it in water, 
and the equilibrium will be instantly de- 
stroyed. To restore it, put into the scale 
from which the body immersed in the wa- 
ter is suspended, as much weight as will 
bring it even with the other scale in which 
the opposing weight remains unaltered. 
The added weight will be equal to that of 
a quantity of water equalling the immersed 
body in bulk. Now if the weight of the 
body in air, be divided by what it weighed 
in the water, the quotient will show how 
much that body is heavier than its bulk of 
water. 
A guinea, new from the Mint, will re- 
quire 129 grains to be offered to its weight 
in air ; but on being immersed in water, 
will require 7\ grains more to restore the 
equilibrium lost by the immersion. From 
this we see, that a quantity of water equal 
in bulk with the guinea weight 7^ grains, 
or 7.25, by which divide 129, (the weight 
in air), and the quotient will be 17.793; 
shewing that the guinea is as 17.793, to 1 
of water. 
But we sometimes have occasion to hs- 
certain the precise weight of bodies that 
are lighter than water, say a piece of cork, 
and which if unaided, would float on its 
surface. In such case, it is necessary to 
affix a weight, (having previously found 
its exact poise) thereto ; when by immers- 
ing both, and deducting the amount of the 
collateral weight, the residue will be left 
to account of the cork. If you would 
weigh quicksilver, it must be first balanced 
in a glass bucket, of which the weight is 
known, and which has been weighed also 
by immersion. When tire bucket has been 
brought to equilibrium in the water, poui- 
in the quicksilver, and the additional 
weight requisite to counterbalance it will 
show its exact weight. 
Perhaps the following general rules for 
finding the specific gravity of bodies may 
prove useful and familiar to every under- 
standing. 1. “ When the bod^ is heavier 
than water,” Weigh it both in water, 
and in the atmosphere, and the difference 
between the results will shew the quantity 
lost in the former mode ; then, as the 
weight lost in water, is to the weight in 
air ; so is the gravity of water to the era- , 
vity of the body. 2. “ When the body being 
specifically lighter, will not sink in water.” 
Kender the body heavy enough to sink by 
means of some appendage, as a small piece 
of lead, &c. ; weigh the body and the 
appendage, both separately and together, 
in the air, and in the water : find out how 
much each loses in the water, and sub- 
tract those losses from the whole weight 
of each in air. Then, as tire last remainder 
is to the weight of the light body in air ; 
