vol.. XXIV.] PHILOSOPHICAL TRANSACTIONS. - 257 



flashes resembling lightning, of a very pale colour, very distinguishable from 

 the rest of the produced light. The flashes seemed then to be darted horizon- 

 tally, though at other times I have observed them to incline upwards, and 

 sometimes downwards, sometimes from divers parts, as well from the outward 

 receiver, as included glass. Sometimes they would be thrown in a figure so 

 odd, that I have no idea of any comparison. I have likewise observed them to 

 proceed directly from the stream of quicksilver, as it descended from the fun- 

 nel, before it reached the included glass. They generally fly to the side of the 

 outer receiver, (unless their origin begins there, as sometimes I have observed) 

 where the light breaks, and spreads in a very odd form. Something farther 

 observable was, that the crown of the included glass appeared sensibly more 

 luminous than any other part of it ; which light was constant, without any 

 alteration, during the descent of the mercury through the funnel, and that was 

 at least 2 minutes of time. The quantity of mercury used for this experiment 

 was about 3 pounds. 



ExPER. VI. Showing that Abundance of Particles of Light are discoverable, 

 by shaking Quicksilver in a Glass even in the open Air. — In some of the fore- 

 going experiments, where I assert that the phosphorus of quicksilver is not pro- 

 ducible but in such a medium, I would there be understood, a light of the 

 same nature and quality of that discovered in the barometer, by putting the 

 mercury in motion ; which light is very different from what is made by shaking 

 mercury in the open air, as was very sensible in 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 its mouth with a 

 brass cap ; in the middle of which was inserted a cock, by which means there 

 was a free communication with the outward air ; thus prepared, the globe was 

 shaken, and the particles of light appeared plentifully, about the size of small 

 pins' heads, very vivid, resembling bright twinkling stars, exhibiting some 

 small faint light, like the whitish appearance of the via lactea. Their numbers 

 increased according to the rapidity of the motion given. I then took the same 

 glass, with the same mercury, and applied it to the pump, by means of a hol- 

 low brass pipe, which screwed on, both to the cock and pump, in manner of 

 fig. 21. The air from within which being exhausted, and the cock turned, to 

 prevents its getting in again, it was taken off, and moderately shaken ; the mer- 

 cury then appeared luminous all round, not as before, like little bright sparks, 

 but a continued circle of light during that motion : but when that motion was 

 checked with another of greater violence, it then appeared luminous almost all 

 over the globe. On suffering the air to return, that mode of light vanished ; 



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