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QQP Gravity and Levity

From Cambridge University Library Add. MS 3996, Questiones Quædam Philosophicæ (Certain Philosophical Questions, now published by McGuire and Tamny.) Square brackets, [ ], are my comments and [ . . . . . . . ] indicates an omitted section. There is also a discussion of the Two Falling Globes section.

Of Gravity & Levity

19 97r

The matter causing gravity must pass through all ye pores of a body. it must ascend againe. 1 for else ye bowells of ye earth must have had large cavitys & inantys to conteine it in 2 or else ye matter must swell it. 3 ye matter yt hath so forcibly borne dow ye earth & all other bodys to ye center (unles you will have it growne to as gross a consistence as ye Earth is, & hardly yn) cannot if added to gether be of a bulke so little as ye Earth, For it must descend exceding fast & swift as appeares by ye falling of bodys, & exceeding weighty pressure to ye Earth. It must ascend in another forme yn it descendeth or else it would have a like force to beare bodys up yt it hath to press ym downe & so there would bee no gravity. It must ascend in a grosser consistence yn it descends 1 because it may be slower & not strike boddys wth so greate a force to impell ym upward 2 yt [this sentence continued on 67 121r ]

Gravity & levity

67 121r

anothers streames wth much difficulty, & pressure & so be compacted & ye descending streame will keepe ym so by continually pressing ym to ye Earth till they arise to ye place from whence they came, & there they will attaine theire former liberty.

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The weight of water is to ye weight of quicsilver as 1 is to 14. Water is 400 (perhaps 2000) times heavier yn aire & gold 19 times heavier yn water.

Quæst: What proportion ye weights of two bodys as gold & silver have have in divers mediums as in vacuo aere aqua &c: wch known ye weight of ye aire or water in vacuo or the quantity of gold to ye silver is given &c

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Try whither flame will descend in Torricellius vacuu.

68 121v

Falling globes diagram In ye descention of a body There is to be considered ye force wch it receives every moment from its gravity (wch must bee least in a swiftest body) & ye opposition it receives from ye aire (wch increaseth in pportion to its switfnesse). To make an experiment concerning this increase of motion When ye Globe a is falne from e to f let ye Globe b begin to move at g soe yt both ye globes fall together at h.

According to Galilæus a iron ball of 100l Florentine (yt is 78l at London of Adverdupois weight) descends an 100 braces Florentine or cubits (or 49,01 Ells, perhaps 66yds) in 5'' of an hower.

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Try whither ye weight of a body may be altered by heate or cold, by dilatation or condensition, beating, poudering, transfering to severall places or sevrall heights or placing a hot or heavy body over it, or under it, or by magnetisme. whither leade or its dust spread abroade, whither a plate flat ways or edg ways is heaviest. Whither ye rays of gravity may bee stopped by reflecting or refracting ym

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The gravity of bodys is as their solidity, because all bodys descend equall spaces in equall times consideration being had to the Resistance of ye aire &c.

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