WATER PROVED A COMPOUND. 429 
the saucer which was licked by it, as Macquer says, that 
the little drops of water were deposited. The chemist, 
however, did not dwell upon this fact; he was not sur- 
prised at what it contains of surprising: he simply cites 
it without any commentary; he does not perceive that 
he was touching a great discovery with his finger. 
Should genius then, in the sciences of observation, 
be reduced to the faculty of asking, at appropriate times, 
why ? 
The physical world enrolls volcanoes that have never 
made but one eruption. It is the same in the intellectual 
world ; for there are men who, after a flash of genius, 
entirely disappear from the history of science. Such 
was Warltire, whom I am here led to cite by the chrono- 
logical order of dates for a truly remarkable experiment. 
At the commencement of the year 1781, this physicist 
imagined that an electric spark could not pass through 
certain gaseous mixtures without occasioning some de- 
cided changes in them. So novel an idea, unsuggested 
by any previous analogy, but of which such happy appli- 
cations have since been made, would have merited for 
its author, I think, some honourable mention on the part of 
the historians of science. Warltire was wrong as to the 
changes that electricity would create, but fortunately for 
him he did foresee that an explosion would accompany 
them. It was therefore that he made the experiment in 
a metallic vase, having enclosed some air and some hy- 
drogen in it. 
Cavendish soon repeated Warltire’s experiment. The 
positive date of his repetition (I call thus all dates re- 
sulting from an authentic deposit, or an academical lec- 
ture, or a printed paper) is anterior to the month of 
April 1783, since Priestley cites Cavendish’s observations 
