Prof. Hare on the Sliding Rod Measurement in Hydrometry. 267 
water counterbalance it, the alcohol must be to the water in 
gravity as 800 to 1000; since it is self-evident, that when any 
two masses are made equal in weight, their gravities must be 
inversely as their bulks. 
To ascertain the Specific Gravity of a Solid, by the Chyometer. 
For this purpose, the body, whose gravity is in question, 
should be suspended in the usual way, beneath one of the 
' scales of a balance, and its weight in parts of water, at 60° Fahr. 
ascertained, by measuring from the chyometer, into the oppo- 
site scale, as many parts as will balance the body. Being thus 
equipoised, and a vessel of pure water, at the same tempera- 
ture as that introduced by the chyometer, duly placed under 
it; the number of parts of water, competent exactly to cause 
it to be merged in this fluid, will be the weight of a quantity 
of water equivalent in bulk to the body. Of course, dividing 
by the number thus observed, the weight of the body in parts 
of water as previously found, the quotient will be the specific 
gravity. 
This process ought to be easily understood, since it differs 
from the usua] process only in using measures of water in- 
stead of the brass weights ordinarily employed. 
The chyometer enables us to make new weights, out of wa- 
ter, for each process. 
To ascertain the Specific Gravity of a Corrosive Fluid, by the 
Chyometer. 
The process described in the preceding page, is only appli~ 
cable where the fluid is not of a nature to act upon the sliding 
rod. By employing a body,—a glass bulb for instance,—ap- 
pended from a balance, as in the usual process, we may use 
water measured by the chyometer, in lieu of weights. 
First, having counterbalanced the body exactly, ascertain 
how many parts of water will cause it to sink in water; next, 
how many parts will cause it to sink in the liquid whose gra- 
vity is to be ascertained. The number last found, being di- 
vided by the first, the quotient is the specific gravity. 
Supposing that the graduation be made to correspond with 
the size of the bulb, so that 1000 parts of pure water will just 
sink the bulb in another portion of the same fluid; the pro- 
cess for any other liquid will be simply to ascertain how many 
arts of water will sink the bulb in it. "The number observed, 
will be the specific gravity; so that recourse to water, or to 
calculation, would be unnecessary. 
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