On the Hydrometer. 235 



the inftrument fo as to accord with the decreafe of gravity 

 which takes place in the fpirit by the increafe of tempera- 

 ture. Therefore the manner of ufing the inftrumenl is as 

 follows : 



Siippofing the temperature to be 50, nothing further is re- 

 quired butlo place the index No. 1 (each being marked fo 

 as eafily to be diflinguifhed) on the fide marked 50^ and irn- 

 incrfe the inftrumcnt, which at once ftiows the ftrength. 

 Should the temperature be 51 or 52, inftead of index No. i, 

 ufe that marked No. 2 : fhould it be 53 or 54, ufe index 

 No. 3 : the inftrument having been adjuded with thefe two 

 auxiliary indexes, in the one cafe at a temperature of 514, 

 and in the other 53^, thefe four intermediate temperatures 

 are fo accorded to, as to be either the actual one, or within 

 half a degree of it. And they apply in all cafes, to the four 

 intermediate degrees of temperature, and no other appendage 

 required to enable the inftrument, in this plain and fimple 

 manner, to meafure fixty-fix gradations of itren-gth with an 

 accuracy which, it is prefunied, is fully fufficient for either 

 revenue or commerce *. No weight requiring difi'erent im- 

 merfions to find out that which is the proper one ; no tem- 

 perature omitted to create doubts, or falle indications of 

 Itrenglh ; no fraftion in the per centage to operate either 

 againil the revenue or the merchant; no gradation ot fi.rengtla 

 left unafcertained or determined by conjeAure ; no doubt re- 

 maining as to the correal ftrength of all the various grada- 

 tions; and no fecond infpcclion and fubfequent combination 

 to be made, requiring the aid of, and liable to the errors of, 

 a (lidiug rule. 



The following is a table for graduating hydrometers on a 

 certain and invariable principle, ihowing from the Ipccific 

 gravity of the fpirit at the temperature 55, what the hydro- 

 meter indication of ftrength fhould be of every poflible mix- 

 ture of pure fpirit (or alcohol) and water, from the former 

 down to proof fpirit. — N. B. This table is calculated ou 

 the fuppojilmi that the ftandard of proof is 922, tempera- 

 ture 55. 



' Even this h..lf degree of temperature may be obtained by holding 

 tilt jar containinj^ ilit fpirit for a few moments in the hand. 



Tabic 



