VOL. XXVIf.] i'HILOSOPHICAL TRANSACTIONS. d45 



considerably, as when it was possessed only by water. And it is to be observed, 

 that though they became very warm, yet, contrary to the nature of most 

 liquors in such a state, they continued to possess less and less space ; which was 

 visible by the sinking of the surface in the stem of the bolt-head; and in about 

 half an hour's time it had descended above an inch; and on viewing it 4 days 

 after, it had subsided at least 7 inches below the mark I had left it at. Now 

 whether the ebullition produced by the heat, might not evaporate that quantity, 

 which it seemed to lose in space ; or whether, in so many hours there might 

 not be such an evaporation of the parts of the fluid, as to become equal in bulk 

 to the quantity of the dispossessed space ; I satisfied myself in the following 

 manner. 



Into an upright glass, that would hold about 3 ounces of water, I put a 

 quantity of the same fluid equal to 885 grains : into another glass of the same 

 form, but smaller, I put a quantity of oil of vitriol equal to 456 grains; which, 

 with their respective glasses, I weighed altogether in a nice balance : after which, 

 I put the oil of vitriol, glass and all, into that which held the water ; where 

 immediately a very great ebullition began, and the glass that contained them 

 became so hot, as to be but just endured in the hand. I found in 2 minutes 

 time it had lost of its weight about 2 grains ; and at the end of an hour, or 

 better, it had decreased in all only 64- grains : by that time the conflict 

 was wholly ceased, it being then nearly reduced to the temperature of the outer 

 air. Afterwards I weighed them at several times, but found them in the same 

 state, as to their weight, as last mentioned. I continued them in the scale till 

 the next morning, when I likewise could distinguish no manner of alteration in 

 the forementioned weight. From whence it plainly appears, that the decrease 

 of bulk on the mixing of these liquors, does not proceed wholly from an eva- 

 poration of their parts; since by the last experiment, the evaporation continued 

 no longer than the fermentation lasted ; but the decrease of bulk in the bodies, 

 seems not to be performed all at once, or in so short a time, as may be observed 

 in the first experiment. 



jiccount of an Experiment, to produce Light through a Metallic Body, under the 

 Circumstances of a Vacuum and Attrition, By Mr. Fr. Hauhsheey F. R. S. 

 N°331, p. 328. 



It may be remembered what success I had in producing light through bodies, 

 such as sealing-wax, pitch, and common sulphur ; which gave me some proba- 

 bility, that under the same circumstances I might likewise make some such dis- 

 covery through a metallic body. Accordingly I caused a glass hemisphere to be 



