enter the Fluid, as Corpufcles of Fire in Steam move Fluids, and the Bodies in them, as they pervade, &c. or by the Preffure of the Atmosphere, or by the. Quality of Gravity, or Elafticity. The fmall Bodies or Maffes in Fluids move, and are moved, by the different Qualities, or different Degrees of Qualities, in them, and the Fluids. Every Mafs of any confiderable Bignefs, immerfed in a Fluid, which weighs more than the fame Bulk or Dimenfion of that Fluid, will fink in it, and every one which weighs less than its Bulk or Dimenfion, will fwim in it. But small Particles or Corpufcles of Bodies, which in Mafs have not much more or lefs Gravity than the Fluid, efpecially if the Particles be extended in Breadth or Length, or the Fluid be in Motion or agitated, will hover or be toffed about in that Fluid and not fink, or rife fuddenly: If they differ much in Gravity, and be of proper Figures for Pervafion, they rife or fall with Celerity, in Proportion to that Difference of Gravity and Fitness of Figure. But the same Matter will be moved in different or oppofite Directions, by altering its Gravity or Figure, or the Gravity of the next neighbouring Bodies or Fluids, by Addition, Subftraction, Multiplication,

A 4.

tiplication, or Divifion, performed amongst themselves, by their other Qualities in their Motion. If a lighter Body be fubftracted, separated, or taken from an heavier Body, the Body lighter than the Fluid will rife, and the Body heavier than it will fink, or reft at the Bottom. If the Number of Bodies which will hover in the Fluid be multiplied, either by adding more Corpufcles of like Gravity, or by dividing the Maffes which funk in it, or &c. for Example, Sea Salt, Sugar, &c. diffolved in Water, the Fluid will be heavier, and those Bodies, which had a little more Gravity and funk in it, will fwim, &e contra. If Bodies which hovered or funk be divided small enough, or have lighter Bodies joined to them, those which fubfided may rife into or fwim upon the Fluid, and those which hovered in it may fwim upon it; nay, even both may rife out of that Fluid, and hover or fwim in a lighter Fluid, as out of Water, into Air, &c. When any Mafs in a Fluid is expanded or ftretched into a Bubble by the Corpufcles of Fire, volatile Salts, Air, &c. till it be lighter than the Fluid, 'tis prefs'd up with Velocity in Proportion to its Difference in Gravity to the Surface, and there fwims

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or bursts, and its Parts fly into or swim in the Air, as thofe of Barm, Soap, &c. or by the Quality of Elafticity, for the lighter the Fluid, the more, fmall Bodies in it, which have Elafticity, will expand or extend themselves, and the Fluid, and then Bodies which fwim in that Fluid will fink; and the heavier the Fluid, the more fuch Bodies will be compreffed in it, and that will make the Fluid ftill heavier, and Bodies, which funk in it before, will then fwim. Or by the Elafticity, or Adhesion of the Parts of Bodies when they are fplit or divided, which jirk upward or downward, this Way or that Way, expand and make the Fluid lighter, and throw themfelves or other Bodies they strike upon, or adhere to, in any Direction or upward, out of the Fluid. Bodies in a Fluid move like Weights in the Scales of a Balance, when one fubfides, others go up with Force and Velocity, proportionable to the Difference in Gravity or Levity to that of the Fluid, the external Impulfe, Preffure, Distance they move, &c. And the Fluids and Bodies next adjoining take their Places, and fo fucceffively others take the Places of them, till the finking Body reft, each of the adjacent be mounted a little high

er,

er, and each placed according to their respective Gravities. When Fluids, &c. fill any Veffel, which may be extended, and whofe Sides are of equal Strength, and equally compreffed; if one Side be preffed more inward than the reft, all the oppofite Sides must be preffed as much in the whole outward; when the Fluids, &c. expand fuch a Veffel, which contains them, it must extend equally in all Parts, their Gravitation upon the Bottom and Sides only differing: If the expanded Fluid gets vent, and iffues out in any part, it will iffue with Force proportionable to that which impells or expands the Fluid, the Compreffure of the Sides of that which contains it, the Straightness of the Aperture, and its own Gravity, if it defcend; only leffened by the Preffure upon the Aperture, and its own Gravity, if it afcend: And that Spout will continue iffuing fo long as the Fluid expands, or rarifies beyond the Capacity of the Veffel: If it be conveyed thence in a Pipe, fhut at the farther End, and empty, which is not more or less compreffed, than that it iffues out of, it will meet with no Refiftance till it come at the End of the Pipe: If the Pipe would widen or ftraighten as the Force within, or the Compreffure without

without prevailed in the whole, or in any one Part more than another, and the Force which drove the Fluid were to operate all at one End, like a Pump or Forcer by Jirks, and the Compreffure without were equal in all Parts, the greateft Force or Strefs would be at the End of the Pipe, next the Pump, it would extend moft, and be liable to burst the fooneft there; and the Extenfion would be ftill leffer at the greater Distance from the Forcer; if the Compreffure were leffened or taken off that or any other Part, it would be more extended there in Proportion, and if the Compreffure were encreased in any Part it would be straightened there in like Proportion. If what expands and drives the Fluid go along with it, or in it, and the Preffure be equal on the outfide, it will be equally expanded in all its Parts. If many Pipes or Tubes never fo flender or weak made of Matter, which will extend to fuch a Degree, environed with a Cafe or Compreffure, fufficient to keep them all from extending beyond that Degree, be equally extended by the fame Force, at the fame Time, till they fill the Cafe, and one prefs against another, be that Force never fo great, none of them will burft; if the

Cafe