On the Hydrometer. 1^^ 



fnre, or 80 bv weight of water. The difference is confidera- 

 bif, but the firft is undoubtedly molt conformable to the 

 cxi-(ting ad:s of parliament : if, therefore, it be thought right 

 to prefcrve the term proof /pirit in our excife laws, it may be 

 underrtood to mean fpirit whofe fpecific gravity is 916, and 

 which is compofed of 100 parts of reftified fpirit at 825, and 

 62 parts of water, by mcafure, or 75 by weight; the whole 

 a.t 60 degrees of heat." 



From this extradl it appears there are no lefs than three 

 imperfections in this manner of defining proof ipirits. Firft, 

 the fpirit defined is not proof, but another fpirit, one lo fix, 

 or one ii I'even, under proof, requiring a fubfequent nrocefs 

 to make proof: fecondly, the difficulty of procuring an exa6t 

 gallon meafure. 



The late ingenious Mr. Ramfden, in a publication on this 

 fubjedt, printed in 1792, fpeaking of the ftandard of proof, 

 fays : " Hydrometer-makers differ on this point 7 1 per cent.; 

 and government, to avoid difputes, have been under the ne- 

 ceffity of palfing an aft to conftitute Clarke's hydrometer (for 

 a fliort time) the only legal one, though it is, in all proba- 

 bility, as vague as any of the others, particularly in fpirits 

 conliderably higher than proof. An obliacle to ai'certaining 

 this term (favs he) arifes from the difficultv of obtaining ^rac^ 

 ttcully the exHiSl capacity of our gallon meafure: it is, in- 

 deed, ftated to contain 231 cubic inches; vet, notwithftand- 

 ing the great pains taken bv a committee of the houfe of 

 commons, about the vear 1758, for that purpofe, allifted by 

 feveral ingenious mechanics, this point was left undeter- 

 mined. The method they ufed was making hollow cubes 

 of different dimenfions, from one inch upwards, which were 

 executed with great care bv the late iVIr. J. Bird, and are now 

 in the repofitory of the houfe of commons : but w hocver con- 

 fiders the difiicvdty of making an exadt cube, and that of 

 afcertaining the infide calibre with precilion, muft be fcnfible 

 that no great reliance can be had on the exa6lnefs of a gallon 

 menfnre obt;iinc(i by this method." 



Thirdly, that no temperature being mentioned, the ftrcngth 

 is doubtful ; and though fir Charles, in this part of his Ke- 

 po!t (which lias not, f believe, been contradided), fays the 

 trade confiders the tem|)erature to be 55, and that proof fpirit 

 fliould be as he liates, by the unerring tell of the fpecific 

 graviiv9i6, at 60, (and which would be 918, at 55 ;) yet 

 the fpecific gravity of proof fpirit, by Clarke's hydrometer, 

 is 9:^, at 5_5 of iem|>crature. 



From this it a[)pears, that even Quin's and Dicas's (land- 

 ards of proof an- erroneous to an ixlcnl of three per cent, j 



and 



