A 
( 178 ) 
Place of the Hydrometer, and (hews the different fpe- 
cifick Gravity of Fluids to a very great Exadnefs. 
Hut as that Balance cannot well be carried in the Pock- 
et, and much lefs managed and underftood by Perfons 
not ufed to Experiments, Mr. Clarke was refolved 
to perfect the Hydrometer for the Ufe of thofe that 
deal in Brandies and Spirits, that by the Ufe of the In- 
flrument they may, by Irifpedion, and without Trou- 
ble, know whether a fpirituous Liquor be Proof, 
above Proof, or under Proof, and exadly how much 
above or under : And this muft be of great Ufe to the 
Officers of the Cuftoms,who examine imported or ex- 
ported Liquors. 
After having made feveral 
fruitlefs Trials with Ivory, be- 
caufe it imbibes fpirituous Li- 
quors, and thereby alters its 
Gravity, he at laft made a 
Copper Hydrometer, reprefented 
hyFlg, z, having a Brafs Wire of 
about iinch thick going through, 
and foldered into the hollow 
Copper Ball, Bb, The upper 
Ball of this Wire is filed flat on 
one Side, for the Stem of the 
Hydrometer, with a Mark at 
to which it finks exaftly in Proof 
Spirits. There are two other 
Marks, A and B, at Top and Bot- 
tom of the Stem, to fhew whe- 
ther the Liquor be A above 
Proof (as udien it finks to A) of 
under Proof (as when it emer- 
' ges 
Fig. a. 
0 
1 
nv 
