VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 100 



inch machine, in water taken from the cistern : and at 12 h 6 m p. m. of the same 

 day, there had been written down 10200 discharges, each of which occasioned air 

 to ascend from the bottom of the wire and brass cup. The quantity of air obtained 

 was now apparently about 4- of a cubical inch, and it occupied nearly £ the tube ; 

 the water in which was by this time very muddy. After standing till the day fol- 

 lowing at noon, when the process was again commenced, it did not appear that any 

 of the gaz had been absorbed by the water over which it stood. 



At 2 h 35 m p. m. began to produce discharges, and at 8 h p. m. had passed 6636 ; 

 which', together with those of the preceding day, amounted to 16836. The tube 

 was now -f full of gaz, and there seemed to be almost 4- a cubical inch ; for it was 

 observed, that the gaz was this day yielded at double the rate it had been the day 

 before. This was accounted for from the diminished pressure on the electric fire, 

 by the tube containing gaz instead of water. At this time, namely, at 8 h p. m., I 

 was surprized, on the passing of a discharge, by a vivid illumination of the whole 

 tube, and a violent commotion within it ; with, at the same time, the rushing up 

 of water, instantly to occupy rather more than £ of the space which had been oc- 

 cupied by gaz. The residue of gaz was not diminished further by an electric 

 6park ; and to the test of nitrous gaz it appeared to be rather worse than atmos- 

 pherical air, as it consisted of rather less than 1 part of oxygen, and 3 parts of 

 nitrogen or azotic gaz. 



It seemed as if the electrical discharge had kindled the oxygen and hydrogen gaz 

 of the decompounded water, by flying from the bottom of the wire to the brass 

 funnel ; so that the fire returned into the tube where it passed through the gaz. 

 Or the combustion might be occasioned by a chain of bubbles, reaching from 

 the brass dish to the surface of the water in the tube, which was set on fire 

 in its ascent, and thus produced combustion of the whole of the gaz of decom- 

 pounded water. That this phenomenon was from the combustion here supposed, 

 was in some degree proved by finding that the mixture of hydrogen and atmosphe- 

 rical air, under the same circumstances, was kindled in the same manner. 



Exper. 2. With a double plate electrical machine, 24 inches in diameter, and a 

 similar apparatus to that in the last experiment, 14600 discharges produced, at 

 least, -»- of a cubical inch of gaz. While I was measuring with a pair of compasses 

 the quantity of gaz produced, the points of them being in contact with the part of 

 the tube occupied by gaz, I was again surprized, on the passing of a discharge, by 

 an illumination of the whole tube, and the rushing up, with considerable commo- 

 tion, of water, to occupy about -f-of the space filled by gaz. The residuary air was 

 found, as in the former experiment, to be rather worse than atmospherical air. 



It was concluded that the points of the compasses had attracted electrical fire 

 from the wire to the sides of the glass, and so kindled the hydrogen and oxygen 

 gaz of decompounded water. But to determine this question, I introduced into 

 the same tube a mixture of 1 measure of oxygen and 2 measures of hydrogen gaz, 

 to occupy nearly the same space in the tube as the gaz had occupied : then passing 



