Opinion on Hydrometers, by Dr. Hare. 11¥ 
and that this alcohol were gradually reduced in strength, by 
the addition of water, the graduation on the stem would have 
to emerge thirty-six times, and be as often submerged by an 
additional weight ; each Weight differing from its predeces- 
sor, by the weight of a quantity of the spirit, equal in bulk to 
the ten divisions on the stem. 
thermometer accompanies the instrument, and, by means of 
a slide in the scale, the numbers fonnd by means of the 
weights and the stem, are slid backwards or forwards, so as 
to lessen or increase the indication of strength, proportiona- 
bly to the temperature. 
If this be a correct account of Dicas’ hydrometer, it will 
be evident, that, when well executed, it must be capable of 
affording correct indications ; and that, any errors or incon- 
sistencies, which may have been discovered in the ob- 
tained by it, may be ascribed either to incorrectness in the 
execution of the instrument, or to its being deteriorated by 
wear, by accident, or abuse. But to these sources of inaccu- 
racy, all instruments, constructed in a similar way, are equal- 
} le: and, while such instruments are used, I cannot 
conceive any other method of preventing error, than that the 
instruments shall all be tried by a scientific and skilful officer, 
before they are used, and periodically passed through his 
hands, for the purpose of rectification, whenever he may find 
it necessary. 
acquainted with the subject, will perceive, that a great num- 
ber of laborious experiments, and calculations, would be re- 
attended by great labour, I do not think that it would essen- 
ially promote the views of government, since the result could 
tency 
* See Gilpin’s Tables. 
