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Hydrostatics.

swim by the superior Force or Pressure of theFluid upwards (LXI).

Hence also the Reason of trying the differentGravity , Denjity, or Strength (as it is common-ly call’d) of divers Fluids or Jpirituous Liquorsby the Hvdr o _ai e t e r or Water-Poise : For,since the stronger any Fluid is, the greaterwill he its Resistance to any Solid immerled,

’tis

PI. XV.Fi g- 3 -

(LXI) Thus for Instance, if the Body M be 5Times heavier than Water of an equal Bulk, and if byMeans of the Tube NO, placed on its upper Surface,the Water be kept from pressing thereon, that it beimmersed to 7 Times its Thickness below the Surface ofthe Water, ’tis plain the Pressure on the under Surfaceupwards will be as 7, but downwards only as 5 ; andtherefore since there is the Excess of two Degrees ofPresiure upward, ’tis plain the Body cannot descend ; butmay very properly be said to twim on the Water, andthis will be the Cafe of all Bodies, however large orheavy, if placed at a proper Depth in the Water, withthe above-mentioned Circumstances.

2. But what is most remarkable, and at the fameTime the clearest Proof of the Hydrostatic Paradox, is,that if the Body M be immerled to the Depth of 10Times its Thickness below the Surface, with a Tube tokeep off the Water from its upper Surface, then what-ever be the Form of the Tube upwards, Water pour’dinto the fame will in all Forms thereof, at the Altitudeof 5 Times the Thickness, make the Pressure on theunder Surface upwards and downwards equal, and con-sequently, if the Altitude be ever so little increased, theBody will descend. If the Body be immersed to aDepth, equal to 12 Times its Thickness, then the Al-titude of the Water pour’d in must be equal to 7 Timesits Thickness, because 7-7-5^12, and so on in all otherDepths, let the Vesiel NO be ever so great or small,provided its Base be equal to the Surface of the Body;the Presiure of the Water pour’d in being proportionalto the Altitude only, and not at all to the Quantitythereof.