Viewing page 241 of 504

This transcription has been completed. Contact us with corrections.

[[start page]]
50)
If any two fluids, differing in their specific gravities, be put into a vessel, the [[underline]] lighter [[/underline]] will make way for the [[underline]] heavier [[/underline]] and stand uppermost and the heavier will rest at bottom; as linseed Oil, put into a vessel of water, will rest at top & the water at bottom: Water put into a vessel of the same Oil, it will make way for the water and both rest in the same situation as before: Mercury, put into a vessel of water, will instantly sink & possess the lowest place, and, at the same time, the water will rise & give place to it: Suppose Water put into a vessel of mercury with a hole at the bottom, the water would remain at top, & all the mercury would run entirely off before any water (Suppose it to fill the hole all the time): Again ^ [[insertion]] if possible, [[/insertion]] let a tube, hermatically sealed at bottom, be fill'd, one half ^ [[insertion]] of the whole length [[/insertion]] with water and the other with Spirits of wine; the water will immediately subside, and fill half the length with pure water and the other, or upper half with the risen Spirits of wine; &c. &c. Hence, if a body falls in a plenum there must be a lighter rise to make room for it; also, if a body rises in a plenum, there must be an heavier pressing into its place; for if it were otherwise, the body, in the first case, could not fall, nor rise in the second case, because there would be no room for them to change places. 
Now it is proved past all doubt that there is a PLENUM throughout all Nature [[underline]] and the subtlist medium or fluid of Light is continually rising [[/underline]], therefore it necessarily follows, as well from the laws of Hydrostatics, as from above, and the similarity of all Fluids, that there must be either some body or fluid continually pressing against this Light to take its place: Is not this, or at least something like it, the Cause and Operation of that effect the [[underline]] Newtonians [[/underline]] call Gravity? From hence may be assigned the cause, why mercury will stand at the height of 70 inches in a Tube V. [[underline]] Newton's [[/underline]] Optics, p. 365. for mercury, being a very fine and dense fluid, will not admit air sufficient to keep the inclosed fire or light in action, much less to put it out of a state of rest in ^ [[insertion]] to [[/insertion]] that of action; so the fire or light remaining quiescent in the mercury, no Air or other substance can press in, to give motion, from what has been asserted above: but if the tube be shaken or jarred with the finger, the inclosed particles of light are put into an undulatory motion, and since this light is the finest, subtlist & rarest fluid or medium it will consequently ascend and the fluid of air will take its place, and thereby a motion ensues, and the mercury immediately subsides & rests at the height of the Barometer [this, to the best of my remembrance, is the manner W.J. accounted for it, tho' it is obscure and unsatisfactory to me now.] S. [superscript]] r [superscript]][[underline]] Isaac Newton [[/underline]] says, it is caused by a strong attraction seated in the Glass Tube itself; but his followers, as Rowning part II. p. 72. say, that the mercury's falling about an immerged Capillary Tube is because the Glass Repells the Mercury; a fine contradiction in plain Terms, making the Glass to be endued with two contrary powers, for the self same effect. W.J.
[[end page]]

Transcription Notes:
Multiple instances of the use of the old style long "s" are present throughout. Transcribed using modern double "s" format. Also, use of ampersand accompanied by a small "c" to represent "etc" is present. This is correct for this time period.