153 On the Hydrometer. 



Until within a period of about forty years, the ftrengths of 

 fpirituous liquors were moftly afcertained by other modes, 

 both in Great Britain, Ireland, and on the Continent. 



Proof by oil, by agitation, by firing gunpowder, by alka- 

 line falls, and by glals bubbles, has been ufed, but in every 

 cafe found defective ; and the hydrometer was at length re- 

 fortcd to, as an indrument calculated to afcertain thefe 

 ftrcngths with lefs trouble and greater accuracy. 



To obtain indications of llrtnglhs by it correftly, how- 

 ever^ depends on circumftances that have not, until lately, 

 been fufficiently underltood or afcertained; on which account 

 the inftrument has been complicated in various ways, by 

 \veights and Hiding rules : thefc, in fome cafes, have rather 

 jncreafcd than diminiflied its irregularity. 



The objecl of the follow-ing inquiry is therefore to bring 

 into one view all the caufes of thole imperfefitions and irre- 

 gularities, and, by fo doing, to prepare the way for their 

 removal. 



Thofe irregularities have arifen from feveral caufes. In 

 the firft place, when Clarke's hydrometer was conftrufted 

 (forty years ago), the effects of expanfion by heal, and con- 

 traction by cold, on the fpecific gravity of fpirituous liquors, 

 bad not been accurately afcertained; nor was the diminution 

 of bulk by penetration (or concentration, as it is improperly 

 called,) well under(iood. 



In this ftate of ignorance of thefe effefts, Clarke's hydro- 

 meter was conceived to be a great improvement on that which 

 had been in ufe before it. Prccifelv the fame kind of advance 

 in improvement had been made in the Irifh hydrometer, fome- 

 vvhat nearly about the fame period. The duty on fpirits in 

 both kingdoms previous to this time was paid only on two 

 denomiudiions, viz. fmgle and double fpirits : the former was 

 proof, or under it, and the latter all fuch as were over, proof ; 

 and this difcriminalion of ftrength was made either by a rude 

 fort of inftrument which hardly defcrvcd the name of hydro- 

 meter, or by dropping oil into the fpirit : if the oil floated, 

 it was called liugle ; if it funk, it was double. 



The prcient Irifli hydrometer was adopted about two or 

 three vears' after Clarke's hvdromcter in England ; botii of 

 which purport'ng to difcriminate the increale of llrcngth by 

 per ccnliiges *, fo as to propoition the additional rate of duty 



to 



'' As this term occurs frequently in tlie followii'g efTays, nnd may not, 

 pcrhnps, be tfcarly vnclerftoocl by all my readers, it may not be amil's to 

 exp'ain it here ; — A fpirituous liquor is faid to be ten per cent, over hy- 

 diotnttcr proof when it is fo ftrong thit one hundred gallons of it will 



admit 



