312

Hydrostatics.

same Time, apd in the same Place, even to a wholeInch, from the different Gravity of the Mercury in oneand the other. Therefore those who publish Registersof the Weather ought to find out and declare to theWorld the specific Gravity of the Quick-silver they usein their Barometers.

7. These Uses he enumerates over and above whatwe have taken Notice of, of a Mechanical and Geome-trical Nature : And to let us know th? high Value hehad for this Science, he thus expresses himself : " As“ little Skill as 1 have in Hydrostatics, I would not“ be debarred from the Use of them for a considerable“ Sum of Money, it having already done me accep-" table Service, and on far more Occasions than I my-“ self first expected, especially in the Examen of Me-" t-.is nd mineral Bodies, and of several mineral Pro-“ ductions." With much more to the same Purport.

(LXVIII) 1. To render this Lecture on Hydrojiaticsmore compleat, I shall here subjoin what relates to theResistance of Mediums, or to the Motion cf Bodiesmoving in a resisting Medium : and to determine rightlyin this Cafe, I shall consider every particular Circum-stance by itself, cæteris paribus , and then represent theWhole connected together. We shall suppose the Caseof a Globe moving in a Fluid of an uniform Density for agiven Time.

2. First, Let the same Globe move with the fameVelocity, first in a denser Fluid, and afterwards in ararer ; then it is plain, the denser the Fluid is, themore Particles the Globe will meet with, and strike ina given T ime ; and therefore the greater will be theRe-action or Resistance of the Fluid : Therefore in thisCafe the liesijiance os the two E'luids will be as their Den~

sites.

3. In the next Place, suppose two different Globes,of the fame Quantity of blatter, to move in the fameFluid with the fame Velocity. As these Globes move,it is evident the Number of Particles they meet andstrike, and therefore by which they are resisted, will beas their Surfaces, or rather as their Half-Surfaces ; andthey areas the Squaresof their Diameters : Consequently,

the