TOL. LVIII.] PHILOSOPHICAL TRANSACTIONS. 881 



of wine was found to be tinged with yellow ; but the aether to this time remains 

 unaltered. By shaking the balls while they are exposed to the light, the whole of 

 the fluid in each will appear luminous when carried into a dark room. The 

 aether gives as much light now as it did at first; but the spirit of wine a little less. 



Exp. 4. He exposed the dry phosphorus, in one of the glass balls mentioned 

 in the first experiment, to the light of the day, by holding it on the outside of a 

 north window about half a minute; after which it was kept in darkness for 2 days 

 and a half, and was then found to shine, by putting the glass ball that contained 

 it into a basin of boiling water. On the morrow it was exposed to the light 

 again ; and after it had been kept 4 days and a half in the dark, it gave light 

 when put into boiling water, though not so much as before. In summer he 

 finds it will not give any light by the heat of boiling water after keeping it 15 

 days; but in winter it will afford a little, after keeping it a month. 



Exp. 5. The phosphorus in each of the 2 glass balls, mentioned in the first 

 experiment, was illuminated at the same time and to the same degree, and 

 carried into a dark room. One of the balls was immediately put into a basin of 

 boiling water, and then the phosphorus in it became much brighter than that in 

 the other, and continued so for a short time, but parted with its light so fast, 

 that in less than 10 minutes it was quite dark. The other phosphorus still gave 

 a considerable degree of light, and remained visible for more than two hours after, 

 when even the heat of the hand would plainly increase its light. 



Bolognian phosphorus is said, by Lemery, and also by Musschenbroek,* to 

 imbibe less light when hot than when cold, as it appears less bright when carried 

 into a dark room. But this appearance may be caused by its parting with the 

 light it has received faster when in the former state, than when in the latter, 

 according to the last experiment ; as it must lose more when hot than when cold, 

 during the time of conveying it from the place where it takes the light, 

 to a place dark enough to observe it in. And this seems to be the cause also, 

 why Bolognian phosphorus never appears so bright after it has been illuminated, 

 and consequently in some measure heated, by the direct beams of the sun, as 

 after it has only been exposed, in the shaded open air, to the common light of 

 the day. 



Exp. 6. The balls used in the last experiment were kept in the dark for two 

 days after, and then each at the same time was put into a basin of boiling 

 water in a dark room ; that which had parted with its light in the hot water be- 

 fore, was not visible ; but the other appeared luminous for a considerable time. 



When the phosphorus has once lost as much of the light it had received as 

 the heat of boiling water will cause it to part with, it has never after been found, 

 if kept in darkness, to give any more light by that degree of heat. But if it be 



• See his Introductio ad Philosophiam Naturalem, § l697. See also § ]70i and l6s6. — Orig. 



