The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

CHAP. XXVII: Several other Passages in Mr. Hobbs's Dia∣logue, examined.

IN this Chapter Mr. Hobbs objects against what our Author delivers, concerning the Cause of the Coliesion of two Marbles; but all that is contain'd in what he here offers, being obviated by what hath been deliver'd under the Title of Fluidity, and Firmness; For a further Confirmation of the Doctrin there deliver'd, I shall add the following Experiments: And,

* 1.1First, If an Aeolipile freed from Air, be, whilst hot, stopp'd with Wax, upon a Perforation of that Wax, the Air will be press'd in to the Cool Aeolipile, whether the Orifice be held down, or Horizontally; which shews, that the Air on each side may press upon the Lower Superficies of the Marble, as well as the Subjacent Pillar of Air, and that the Air is not impell'd against it only in a Pyramidal Figure, as he would urge, viz. be∣cause Lines drawn from the Circumference and Borders of the Stones, to the Center of the Earth, must form Pyramids.

To which it might be added, That Part of the Air being drawn out of a large Glass, and a Book clapp'd upon the Orifice, the Pressure of the Sub∣jacent Atmosphere, kept it suspended there.

And the Author of the Magdeburg Experiment says, That two Plates of Copper, whose Diame∣ter was about half an Ell, stuck so close to each other, that six Men could not pull them asund.

* 1.2And it appears from an Experiment made in a Glass Viol, anon to be describ'd, that if the Tube be so immers'd, that it's Lower Orifice just touch the Water, the oblique Pressure of the Atmosphere, will raise the Water in the Tube, a considerable Height, as the Air is suck'd out of the Tube.

Mr. Hobbs objects against the Author's Expli∣cations of the Rising of: Water in Glass Foun∣tains; and says, That it cannot be accounted for by the Expansion of the Air, since the Parts of the Air expanded, take up no more room after they are expanded, than before; but since he means so as adequately to fill more Space; and we only mean such an Expansion, as is before ex∣plan'd, by instancing compress'd Wool; it ap∣pears, that in our Sense it will take up more Space, so as to keep the gross Parts of Water from getting betwixt them.

There are other Objections mention'd in this Chapter, as well as some other Particulars, rela∣ting to the Royal Society; but since the Author finds no weight in them against any thing he hath taught; I shall only further take Notice of what Mr. Hobbs and Gassendus teach, concerning the Rise of Water in Syphons; viz. That it is perform∣ed by Suction. But not now to mention what hath elsewhere been deliver'd to prove the contrary, I shall only add the following Experiment: Ha∣ving taken a Glass Vessel, which was large enough to contain about a Pound of Water, I caus'd a Glass Pipe to be fix'd in the Neck of it; so that the Air within was kept from having any Inter∣course with that without, the Lower End reach∣ing almost to the Bottom of the Vessel: The Pipe being thus fix'd, we convey'd Water into the Bot∣tle,

till it rose something above the Bottom of the Pipe, and then having inclin'd the Bottle to give a due Intercourse betwixt the Internal and Ex∣ternal Air, I suck'd the Air out of the Tube, till the Water rose into my Mouth, and till the Spring of the Included Air, was able no longer to lift up the Water; which would not have done, been were the Common Notion of Suction allow'd, viz. That it is effected by the Pressure of the Air, thrust away by the dilated Chest of him that sucks, and thereby drawing the Water into the Pipe at which he sucks.

But besides the Preceding use made of this Ex∣periment, I pour'd out the Water, till the lower End of the Pipe was but just immers'd in it; and upon Suction, it rose almost to the Top of the Pipe; but the Spring of the Air being too much weaken'd to raise it higher, several Bubbles of Air broke through the Water; but as soon as I left off sucking, the Pressure of the External Air so compress'd the Rarify'd Air within, as to bring it to it's wonted Station, several Particles breaking into the Bottle through the Water, till that Internal Air was equally press'd with the External.

Notes

• * 1.1

  The Pressure of the Air upon Bodies contain'd in it, prov'd.
• * 1.2

  See Fig. 6. Plate second