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XLI. On the Application of the Sliding Rod Measurement in 
Hydrometry. By Rosert Hare, M.D. Professor of Che- 
mistry in the University of Pennsylvania*. 
(THERE is, in my opinion, no mode of measuring fluids, 
heretofore contrived, so accurate and convenient, as that 
which I have employed in my eudiometers. I allude to the 
contrivance of a rod, or piston, sliding through a collar of 
leathers into a tube, and expelling from it any contained fluid, 
in quantities measured by degrees marked upon the rod; and 
ascertained, with additional accuracy, by means of a vernier. 
One of the most advantageous applications of the mechanism 
alluded to is, in ascertaining specific gravities, in the case either 
of liquids or solids. ‘To assay liquids which are not corrosive, 
I have employed two instruments like that represented in the 
following figure, severally graduated to 100 degrees, and fur- 
nished with a vernier, by which those degrees may be divided 
into tenths, and each scale made equivalent to 1000 parts. 
In order to avoid circumlocution, I shall, to the instrument 
here represented, give the name of Chyometer; from the Greek 
chuo, to pour, and meter, measure. 
Supposing two such instruments to be filled, to the extent 
of the graduation, one with pure water, the other with any 
spirituous liquid, lighter than water, whose gravity is to be. 
found ; let 1000 parts of the liquid be excluded into one scale 
of a beam, and then exclude into the other scale as much water 
as will balance it. Inspecting the graduation of the chyome- 
ter, from which the water has been expelled, the numbers ob- 
served will be the answer sought. For, supposing 1000 mea- 
sures of alcohol were placed in one scale, if S00 measures of 
* Communicated by the Author. 
water 
