Page:Philosophical Transactions - Volume 024.djvu/671

from what is made by shaking Mercury in the Open Air, as was very sensible at the making of this Experiment. For, having put into a clean Glass Globe, (whose Content was equal to about 30 ounces of Water) about half a pound of pure Quicksilver, then closing the mouth of it with a Brass Cap, in whose middle was inserted a Cock, by means of which a liberty was given for a free Communication with the Outward Air: Thus prepared, the Globe was shaken, and the Particles of Light appear'd plentifully, about the bigness of small Pins heads, very vivid, resembling bright twinkling Stars, exhibiting some small faint Light, like the whitish Appearance of the Via Lactea. Their Number increas'd according to the Rapidity of the Motion given. This being the whole product of the Experiment in the Open Air, I then took the same Glass, with the same Mercury, and apply'd it to the Pump, by means of a hollow Brass Pipe, which screw'd both to the Cock and Pump (in manner of Fig. 4.) The Air from within which being withdrawn, and the Cock turn'd, to prevent its getting in again, it was taken off, and moderately shaken; the Mercury then did appear Luminous all round, not as before, like little bright Sparks, but as a Continu'd Circle of Light during that motion: But when that Motion was check'd with another of greater Violence, it then appear'd Luminous almost all over the Globe. Upon suffering the Air to return, that mode of Light vanish'd, nor could any thing be Recover'd by shaking, but only the bright Sparks, as at first.

VI. An