ofi 6 Sir Humphry Davy on the state of water , &c. 
no distinct taste, but a smell resembling naphtha ; a portion 
of it taken out mixed with the water, when exposed to heat 
acted like fixed oil, and it seemed to have a high temper- 
ature of ebullition. It inflamed, producing a white smoke. 
The fact, of almost a perfect vacuum existing in a cavity 
containing an expansible but difficultly volatile substance, may 
be considered as highly favourable to the theory of the 
igneous origin of crystals : the other experiment is of a nature 
entirely different, though its result may be explained in the 
same supposition. 
In examining a crystal in the collection of the Royal Insti- 
tution, and which from its characters I believe to be from 
Capao d’Olanda, Province of Minas Geraes, Brazil, I observed 
that the quantity of aeriform matter was unusually small in 
proportion to the quantity of fluid, in two or three cavities 
not occupying — or f- of the space ; and from the peculiarity 
of its motion, it appeared to be more likely to be compressed, 
than rarefied elastic fluid ; and in piercing the sides of the 
cavities I found that this was the case ; it enlarged in volume 
from ten to twelve times; the fluid was water, but the gas 
was too minute in quantity to be examined. 
It will be interesting to ascertain under what circumstances, 
and in w hat situations crystals of this kind are found. If they 
be supposed of igneous origin, they must have been formed 
under an immense weight of atmosphere or fluid, sufficient to 
produce a compression much more than adequate to compen- 
sate for the expansive effects of heat, a supposition which, in 
consequence of Mr. Perkins’s experiments, already alluded 
to, may be easily formed. 
July 6 , 1822. 
