Page:Philosophical Transactions - Volume 024.djvu/708

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k. k. Two Pillars with Nutts to screw down a piece of Board, which has an Iron fasten'd to it to receive the upper point of the Spindle, the lower one falling into a Brass Socket, screw'd to the middle of the Plate of the Air Pump.

l. l. The Supporters reaching from the upper Board of the Ladder to the Pillars, to prevent the Recipients being drawn from its place by the motion and tug of the Wheel-band.

m. m. The small Wheel which the Band surrounds from the great one, and is 1 Inch and a half diameter.

n. n. The Winch which gives motion to the whole. The small Wheel m. m. making about 15 Revolutions to one of the large Wheel D. D. so that a Body fastned to the Spindle g. g. of the small Wheel m. m. must be turn'd 15 times round to once of the great Wheel; and according as it shall exceed in Diameter the small Wheel, so will the Velocity of the Motion of the Extreme parts be proportionably encreas'd.

o. o. Are two Screws which fasten the Ladder to the Floor.

Experiment I.

An Account of an Experiment made Novemb. 21. 1705. at a Meeting of the Royal Society at Gresham College, shewing that Light is Producibile upon a swift Attrition of Amber on Woollen in Vacuo.

Being prepar'd with the Machine before describ'd, for giving a swift motion to Bodies in Vacuo, the Amber made use of in this Experiment was Beads, about the bigness of small Nutmegs, and Threaded; by which means a piece of Wood was surrounded with them, which I had purposely caus'd to be Turn'd, with a Groove on the edge of it, to keep the Beads from being displac'd upon a smartAttri-

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