efcaped from the hand, but was invifible till' if had pafs'd through both glaffes, viz. till it came to the infide of the exhaufted glass, where it appeared like a flash of lightning.

That it efcap'd out of his hand cannot be doubted, fince it did not appear but at the proach of his hand,

ap

170. The following experiment is another, of Mr. Haukfbee's, illuftrating the above doctrine: I fhall therefore give his defcription of it in his own words, with his fentiments thereon in the enfuing chapter...

CHAP. VII. PART I.

SECTION 1.

Mr. Haukfbee's Experiments continued with others tending to point out the fame Agent, by means of its exceffive rapid Motion towards the part moft. rarified.

I

Have difcover'd' fays Mr. Haukfbee fome properties of this electrical matter, which may feem wonderful to those who nicely confider them; fince they afford us a fort of reprefentation of • the great Phanomena of the univerfe. For, having obferv'd that light bodies, placed near any part of the rubbed cylinder, feemed to

• be

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be equally attracted, I contriv'd a femicircle of wire, which I cou'd faften at a constant diftance, making it encompass the upper femicylindrical furface of the glass at 4 or 5 inches diftance: This wire had feveral pieces of woollen thread faften'd to it, fo as to hang down from it at pretty nearly equal distances: The length of them was fuch, that being extended in a direction towards the center of that imaginary circle on the furface of the glafs, in the plane of which the wire was placed, they wou'd then reach within lefs than an inch of the circumference of that circle; but if left to their own liberty, they hung in a parallel pofition to each other. The cylinder was placed with its axis paral •lel to the horizon, and in this posture it was • turn'd swiftly about; and then by the rapid • motion and agitation of the furrounding air, the threads were lifted up and bent upwards from the axis of the cylinder.

All this while, here was only the swift motion of the cylinder round its axis without any attrition. But now, when I came to apply my hand to the lower part of this glafs (fo fwiftly whirl'd about) and confequently to add attrition to the former motion, the threads prefently began to change their directi• on, and all harmoniously pointed to the center of the circle, in whofe plane the wire was

Rather to the Place of Attrition.

pla

placed Neither were they at all diforder'd or flung out of that pofition, by the wind • occafion'd by that violent motion; but (as if there had been no fuch hurry of the air about them) they still perfifted in their cen⚫tral direction. And to render it moft fenfibly convincing, how abfolutely this effect depended upon the attrition, I found I cou'd by fhifting the place of the attrition hither or thither, draw the threads towards this or that • end of the cylinder; but yet they all still went uniformly converging towards fome center in ⚫ the axis of it, fo that they form'd themselves into a fort of conical furface."

"Farther; if the wire with its loofe threads were revers'd fo as to encompass the lower part of the cylinder, (as before it did the upper part;) yet the effect ftill anfwer'd with the fame exactnefs; for the threads were all erected into fo many trait lines, fill directing themfelves to a Center in the axis of the glass.

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172. "Hitherto the axis of the cylinder was placed horizontally: In the next place, I fet it in a vertical pofition, fo that it flood perpendicular to the plane of the horizon, in which cafe, I made ufe of a wire hoop, which was neceffarily to be placed parallel to the horizon, fo that it might encompass the cylinder in the fame manner as the femicircular wire did before: Only one part of the circular wire was left open, to make way for the touch of the hand which was to give the attrition. And the

wire being thus placed it was evident that the threads (without fome external force to fupport them) must all flag, and hang perpendicu larly downwards. Yet, as foon as the motion and attrition were given, the threads prefently began to be extended; and, as if they were become stiff and hard, form'd themselves into an horizontal plane, their loofe ends pointing to a center in the axis of the glass, as before.

173...And thus in all forts of pofitions what foever, both of the wire, and of the glafs too, were the threads acted by a fort of centripetal force, to the laws of which they were always comformable. Haukefbee's Exper. p. 67. to 70.

174. Again. I took an Hemispherical glafs of about fix inches diameter: Into this I conveyed a stick, in 'manner of an axis, which had the woollen threads (formerly made ufe of) tied about it: The glafs was • fcrew'd by the neck to one fide of the spindles ⚫ and being fix'd on the machine, the great * wheel was turned, and the friction made on the outward furface of the glass, as usual. And now the threads prefented a Phænomenon, not a little pleafant and furprifing to ⚫behold; but yet fuch as I expected and hoped for, in the contrivance of this particular Apparatus. For here was just the reverfe of what happen'd when the femicircular wire was placed on the outfide: That is, the threads here, iffued like rays from a center N · out

outwards; as there, they converged to a center within. Mr. Haukefbee's Exper. p. 76. 175. I fhall now endeavour to folve the Phænomena from the vifible effects: -The limits furrounding Mr. Haukefbee's revolving glafs were rarified by the attrition of the hand on the furface: That is, the air furrounding the glass was buoy'd up and borne away from it by the vastness of the elafticity of the accumulating Æther: The Air being thus difplaced from the included limits; thofe limits may then be esteem'd fimilar to an exhausted glass Receiver, and they do in reality appear fo from the effects; for the Pneuma then rushing violently into those rare limits to restore the equilibrium, impels or drives thofe loose ends of the woollen Threads towards the most rarified part; i. e. to whatever part of the Cylinder the

+Since in both Cafes the extremities of the Threads pointed to the furface of the Glafs, viz. where the Friction was made; is it not more reasonable to fuppofe, that thofe extremities of the Threads were affected by that rubb'd Surface, ra ther than its Center, where there was no attrition?

It cannot be the Air, which drives a feather or other light body into thofe rare limits furrounding the rubbed glafs, the Air being firft driven away from it by the accumulating elaftic fluid furrounding it; confequently the effects proceeded from the fame fubtile Pneuma rufhing into the artificial vacuum with that rapidity which caufed the Threads to ap pear ftrait and stiff,

rub