156 Dr. Pearson's Experiments and Observations 
§ 3 - 
The following conclusions appear to me obvious and incon- 
trovertible. 
The mere concussion by the electric discharges seems to 
extricate not only the air dissolved 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 extri- 
cating 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 one-fifth of its bulk of air, when placed 
under the receiver of Mr. Cuthbertson's most powerful air 
pump; but, in the same situation, New River water taken from 
a tub exposed to the atmosphere for a long time yielded its 
own bulk of air. Hence the gaz produced by the first one, 
two, or even three hundred explosions in water, containing 
its natural quantity of air, is diminished very little by an elec- 
trical 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 pro- 
cess for extricating it. 
The nature of the gaz, which instantly disappears on passing 
through it an electric spark, is shown by 
