392 Mr. Nkholjon's Dc/cription of anew Inftrument 



So is the number exprefTing the upper diftance, 



To the lower weight, when the inftrument 

 has no tendency to any one pofition. 



This laft found weighs muft bg confiderably 

 increafed, in order that the inftruments may ac- 

 quire and preferve a perpendicular pofition. 



Add together, into one fum, the weight of the 

 lower fcale thus found, the weight of the upper 

 fcale and its load, and the eftimate weight of 

 the ball and vC^fe. Fintl the folid content of 

 an equal weight of water ; and thence, by the 

 common rules of menfuration the diameter of 

 9n equal fphere. This will be the diameter, 

 from outfide to outfide, of the globe that will 

 float the whole. 



As this procefs, and every other part of the 

 prefent letter, may be eafily deduced from the 

 well known laws of hydroftatics j I forbear en- 

 larging on the denlonllrative part, and fhall pro- 

 ceed to indicate the ufc of the inftrument in the 

 fame curfory manner. 



To merfure the J'pecijic gravities^ and ther- 

 'mometrical expanfions, of fluids. If the extreme 

 length or height of the inftrument be moderate, 

 its weight, when loaded, will be about 3100 

 grains. It is, however, neceflary in praflice, 

 that its weight fhould be accurately found by 

 experiment. This whole weight is equal to that 

 of a quantify of diftilled water, at the tempera- 

 ture of 60*, whofe bulk is equal to that part of 



'th§ 



