for meafuring the Specific Gravity of Bodies, 393 



the inftrument which is below the middle of 

 the ftem. If, therefore, the inftrument be im- 

 merfed to the middle of the ftem, in any other 

 fluid at the fame temperature (which may be 

 done by altering the load) the difference between 

 this laft load and 1000 grains, will be the differ- 

 ence between equal bulks of water, and of the 

 other fluid, the weight of the mafs of water be- 

 ing known to be 3100 grains. If the faid dif- 

 ference be excefs above 1000 grains it muft be 

 added, or if it be dfcf fubtrafted from 3100 

 grains : the fum or remainder will be a number, 

 whofe ratio to 3100 will exprefs the ratio of the 

 fpecific gravity of the affumed fluid to that of 

 water. And this ratio will be expreficd with 

 confiderable accuracy; for the inftrument hav- 

 ing a cylindrical ftem of no more than ^ of an 

 inch diameter, will be raifed or depreflTed near 

 one inch by the fubcradion or addition of tV of 

 a grain, and will therefore indicate with eafe 

 fuch mutations of weight as do not fall fliort 

 of _'g of a grain, or -sir-octh part of the whole. 

 Confcquently, the fpecific gravities of all fluids, 

 in which this inftrument can be immeifed, will 

 be found to five places of figures. 



It is evident, that this inftrument is a kind 

 of thermometer^ perhaps better adapted than 

 the common one, for meafuring the expanfions 

 of fluids by heat. As the fluid, in the common 

 thermometer, rifcs by the excefs of expanfion 



of 



