On the Ilyihomefiir. 233 



■pair of fcales*, of which there are vnrionsyj'^.t's and drfcrip- 

 tions, 10 anfwcr different purpofes, by whicli means their 6m- 

 plicity is unifornily'prefcrved. 



On the contrary, it has crroneoufly been conceived, that 

 an hydrometer would be imperfect that did not, by one means 

 or another, afcertain the fpecilic gravity ot all liquids at their 

 various temperatures: the iiniple power of every inlirument 

 of this kind being confined within certain limits, this could 

 not be efliefted witliout additional complications of various 

 kinds to thofe which were added, to increafe its fenfibility, 

 fome of which are certainly ingenious, but, I conceive, 

 highly unfit for the piirpufe o[ revenue. 



Should this ingenuity be exercifed on a pair of fcales, 

 which it would be proper to ufe in weighing a portion of 

 eight or ten pounds, and by complex additions render them 

 fufficiently fenfible to afcertain a few grains or frattion of a 

 grain, or fo extended in their power as lo weigh lOO pounds, 

 is it not evident that the fimplicitv of the balance, which is 

 its great recommendation, would be deUroycd ? 



That which led to the conftruclion which I finally fixed 

 on, was firfl: a quadrangular Jiein, from which I had four 

 temperatures, viz. ^tSi 45-> 55? and 65 ; and the intermediate 

 det2;rees I managed with four fmall weiiihts on the top of the 

 flem, each ferving for two degrees of temperature. The 

 inftrument having been graduated with thcfe on, if the tem- 

 perature flioiild be two degrees higher than the fcale, I re- 

 moved one weiirht, in order to lighten the iiiRrument equal 

 to the decreafe of fpecific gravity; i^ four degrees, 1 removed 

 two vt'cights ; \^ Jix degrees, I removed three weights ; and 

 \i eight degrees, I removed the fourth; and two degrees more 

 brought me to a new fcale, or fide of the item : by this means 

 the iiilirument would accord with the variations arifing from 

 temperature, fo far as at moft to be but one degree dilfcrcnt 

 from it. It was adjulled at every tenth degree of tempera- 

 ture. 



This was evidently a confiderable progrefs towards the ob- 

 ject I was in |Hirfiiit of, as it not only remedied the great de- 

 it.el of inattention to temperature which took place in the 

 Irifh hvdronuter, but, in a great meafure, the various defefts 

 of the Knglilh revenue hydrometer, as, notwilhilaiiding the 

 weights were reduced from 36 to 4, it accorded nearly with 



• The name of the i/iftrumtnt. which in flriiTncfs fljould be arcomerer, 

 (hydrdiTieitr hcinij an inftrunitnt for vvtinhin;^ water), (ienioilVrM-s this 

 ro be the |)iiiici|iiL on which it ai'ts ; thtitfoic in Kiar.cc it is cdiitd pfje 

 ii<jii(W , and by Ionic Enghlh wiutrs, a waicr-poilie. 



the 



