of the Sliding Rod Measurement in Hydrometry, 271. 
toral scale would answer. Thus prepared, it were unneces- 
sary to have recourse to water, excepting in the first adjust- 
ment of the scale. The number of parts required to merge 
the bulb in any fluid, will reach (at once or twice) the number 
or numbers, on the sector, which give the required gravity. 
In this process if greater accuracy be desirable, it is only 
necessary to employ a smaller rod or a larger bulb. Instead 
of effecting an immersion by one stroke of the rod, it may be 
done by ten strokes, which will make each division of the sec- 
tor indicate a thousandth of the bulk of the bulb. 
The following process is, however, preferable, as the sector 
is made to give the answer in thousandths, without the delay 
of filling and emptying the chyometer more than once. 
_ Let the distance on the rod of the chyometer be ascertained ; 
which, when introduced five times successively, will exclude 
just water enough to overcome the resistance encountered by 
a globe, in sinking in that fluid. Let the sector be opened, 
to the distance so designated: let the globe be partially coun- 
terpoised, so as to float in any liquid heavier than 800. The 
apparatus being thus prepared, if the globe be placed in a li- 
quid, in which it floats, add as much water, from the chyo- 
meter to the scale, from which it hangs, as will sink it ; and, 
by means of the points and the sector, ascertain the value of 
the distance to which the rod has been introduced. Addin 
the numbers thus found to 800, the sum will be the specific 
gravity of the liquid. 
For this process the sector should be divided into 200 parts ; 
and the proper opening being once duly ascertained, should 
be preserved by means of an arc like that attached to common 
beam compasses. 
Instead of a globe, a hydrometer surmounted with a cup, 
may be employed, either with a graduated or a sectoral chyo~ 
meter. 
Before taking leave of the reader, it may be proper to ex- 
plain the use of the square dish, which may be seen to the left 
under the beam (fig. 5). The are of wire is for the purpose 
of suspending the dish tothe hook, in place of the outer bucket. 
When so suspended, filled with water, and duly balanced, it 
will be found soon to become sensibly lighter, in consequence 
of the evaporation of the water. By means of the chyometer, 
it is easy to ascertain the different quantities evaporated, in 
similar times, at different periods, and in different places; so 
that, guarding against the effect of aérial currents, hydrome- 
trical observations may be made with great accuracy. 
In lieu of having points attached to the chyometer, as re- 
presented in the figure, it may be as convenient to have i 
sma 
