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enter the Fluid, as Corpuscles of Fire in Steam move Fluids, and the Bodies in them, as they pervade, &c. or by the Pressure of the Atmosphere, or by the . Quality of Gravity, or Elasticity. "The small Budies or Maffes in Fluids move, and are moved, by the different Qualities, or different Degrees of Qualities, in them, and the Fluids. Every Mass of any considerable Bigness, immersed in a Fluid, which weighs more than the fame Bulk or Dimension of that Fluid, will sink in it, and every one which weighs less than its Bulk or Dimension, will swim in it. But small Particles or Corpuscles of Bodies, which in Mass have not much more or less Gravity than the Fluid, especially if the Particles be extended in Breadth or Length, or the Fluid be in Motion or agitated, will hover or be tossed about in that Fluid and not sink, or rise suddenly : If they differ much in Gravity, and be of proper Figures for Pervasion, they rise or fall with Celerity, in Proportion to that Difference of Gravity and Fitness of Figure. But the fame Matter will be moved in different or opposite Directions, by altering its Gravity or Figure, or the Gram vity of the next neighbouring Bodies or Fluids, by Addition, Substraction, Mul

A 4. tiplication,

tiplication, or Division, performed amongst themselves, by their other Qualities in their Motion.' If a lighter Body be subItracted, separated, or taken from an hea, vier Body, the Body lighter than the Fluid will rise, and the Body heavier than it will fink, or rest at the Bottom. If the Number of Bodies which will hover

in the Fluid be multiplied, either by add· ing more Corpuscles of like Gravity, or

by dividing the Masses which sunk 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 swim, & e contra. If Bodies which hovered or sunk be divided small enough, or have lighter Bodies, joined to them, those which subsided may rise into or swim upon the Fluid, and those which hovered in it may swim upon it; nay, even both may rise out of that Fluid, and hover or swim in a lighter Fluid, as out of Water, into Air, &c. When any Mass in a Fluid is expanded or stretched into a Bubble by the Corpuscles of Fire, volatile Salts, Air, &c. till it be lighter than the Fluid, 'tis press’d up with Velocity in Proportion to its Difference in Gravity to the Surface, and there swims

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or bursts, and its Parts fly into or swim in the Air, as those of Barm, Soap, &c. or by the Quality of Elasticity, for the lighter the Fluid, the more, small Bodies in it, which have Elasticity, will expand or • extend themselves, and the Fluid, and then Bodies which swim in that Fluid will fink; and the heavier the Fluid, the more such Bodies will be compressed in it, and that will make the Fluid still heavier, and Bodies, which funk in it before, will then swim. Or by the Ela{ticity, or Adhesion of the Parts of Bodies when they are split or divided, which jirk upward or downward, this Way or that Way, expand and make the Fluid lighter, and throw themselves or other Bodies they strike upon, or adhere to, in any Direciion or upward, out of the Fluid. Bodies in a Fluid move like Weights in the Scales of a Balance, when one subfides, others go up with Force and Velocity, proportionable to the Difference in Gravity or Levity to that of the Fluid, the external Impulse, Pressure, Distance they move, &c. And the Fluids and Bodies next adjoining take their Places, and so successively others take the Places of them, till the finking Body rest, each of the adjacent be mounted a little high

er, and each placed according to their respective Gravities. When Fluids, &c. fill any Vessel, which may be extended, and whose Sides are of equal Strength, and equally compressed ; if one side be preffed more inward than the rest, all the opposite Sides must be pressed as much in the whole outward; when the Fluids, &c. expand such a Vessel, 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 issues out in any part, it will issue with Force proportionable to that which impells or expands the Fluid, the Compressure of the sides of that which contains it, the Straightness of the Aperture, and its own Gravity, if it descend; only lessened by the Pressure upon the Aperture, and its own Gravity, if it ascend: And that Spout will continue issuing so long as the Fluid expands, or rarifies beyond the Capacity of the Vessel: If it be conveyed thence in a Pipe, shut at the farther End, and empty, which is not more or less compressed, than that it issues out of, it will meet with no Resistance till it come at the End of the Pipe: If the Pipe would widen or straighten as the Force within, or the Compressure


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 greatest Force or Stress would be at the End of the Pipe, next the Pump, it would extend most, and be liable to burst the foonest there ; and the Extension would be still lesser at the greater Distance from the Forcer ; if the Compressure were lessened or taken off that or any other Part, it would be more extended there in Proportion, and if the Compressure 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 Pressure be equal on the outside, it will be equally expanded in all its Parts. If many Pipes or Tubes never so slender or weak made of Matter, which will extend to such a Degree, environed with a Cafe or Compressure, sufficient to keep them all from extending beyond that Degree, be equally extended by the same Force, at the same Time, till they fill the Case, and one press against another, be that Force never so great, none of them will burit ; if the i


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