TOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. ] 1 1 



diminution took place. To this residue 4- its bulk of oxygen gaz was added, and 

 this mixture of gazes being well dried by standing over lime and boiled quicksilver, 

 an electric spark was passed through it, by which a diminution of -£- of its bulk 

 took place. A little dew was then seen on the sides of the tube where the quick- 

 silver had risen ; and, with the aid of a lens, the same appearance was perceived on 

 the part of the tube containing the residue of gaz. 



It may now be expected, that I should have made the experiments with this ap- 

 paratus on distilled water freed from its air, not only by long boiling, or the air- 

 pump, but by passing through it several hundred electrical discharges. It would 

 also have been, to some persons, more satisfactory, if the experiments had been made 

 on a larger scale, so as to have produced the combustion of a much larger quan- 

 tity of gaz, and consequently have produced a greater quantity of water. As how- 

 ever I apprehend that the experiments contained in this paper, when well considered 

 by competent judges, will be found to explain the nature of the gaz procured from 

 water by electrical discharges ; and as another very important subject demands my 

 attention, the honour of more splendid and convincing experiments must be reserved 

 for other inquirers. If the same sacrifices be made by them, which have been 

 made in performing the present experiments, I think it is scarcely possible but that 

 still further light concerning the composition of water should be obtained, as well 

 as concerning oils, alcohol, acids, &c. ; to the investigation of the composition of 

 which, the mode of analysis and synthesis here indicated, may be applied. 



^ 3. The following conclusions appear to me obvious and incontrovertible. The 

 mere concussion by the electric discharges seems to extricate not only the air dis- 

 solved in water, which can be separated from it by boiling and the air-pump, but 

 also that which remains in water, notwithstanding these means of extricating it 

 have been employed. The quantity of this air varies in the same and in different 

 waters, according to circumstances. New River water from the cistern yielded 4. 

 of its bulk of air, when placed under the receiver of Mr. Cuthbertson's most pow- 

 erful air-pump ; but in the same situation New River water, taken from a tub ex- 

 posed to the atmosphere for a long time, yielded its own bulk of air. Hence the 

 gaz produced by the first 1,2, or even 300 explosions in water, containing its na- 

 tural quantity of air, is diminished very little by an electrical spark. 



The gaz or air, thus separable from water, like atmospherical air, consists of 

 oxygen and nitrogen or azotic gaz ; which may be in exactly the same proportions 

 as in atmospherical air, for the water may retain one kind of gaz more tenaciously 

 than the other ; and on this account the air separated may be better or worse than 

 atmospherical air, in different periods of the process for extricating it. The nature 

 of the gaz, which instantly disappears on passing through it an electric spark, is 

 shown by 



(a) This very property of thus diminishing ; and by the following properties ; 



(b) A certain quantity of nitrous gaz instantly disappeared, apparently composing 

 nitrous acid, on being added to the gaz (a) h., exp. 4 ; oxygen gaz being added to 



