37 © Sir Humphry Davy on the state of water 
marked upon the crystal. The chemical nature of the fluid 
and gas was determined by processes which were necessarily 
difficult from the smallness of the quantities operated upon ; 
but which are too well known to the chemical philosophers 
of this Society to need description. 
The first three crystals that I examined were from Schem- 
nitz, in Hungary ; the cavities that they contained were proved 
not to be permeable to the atmosphere, by exposure to rare- 
fied air, alone, and under water, in the receiver of an air 
pump, a circumstance which it was necessary always to attend 
to, in order to render the experiment availing. 
A cavity in one of the crystals was pierced under oil, 
three under distilled water, and one under mercury. In all 
of them the fluid rushed in when the cavity was opened, and 
the globule of elastic fluid contracted so as to appear from 
six to ten times less than before the experiment. The fluid 
in all the crystals (in two it was minutely examined) was 
found to be water nearly pure, containing only a minute por- 
tion of the alkaline sulphates; The elastic fluid, as well as I 
could ascertain from the very minute quantities I could procure, 
appeared to be azote, unmixed with any other substance. 
The largest cavity, which was in the crystal put into my 
hands by Professor Buckland, contained a space equal to 
74*5 grains of mercury; the water in it equalled in volume 
4,8.1 grain measures of mercury; and the globule of air, 
after the experiment, equalled in diameter a globule of mer- 
cury weighing 4.2 grains, so that the elastic fluid had con- 
tracted at least between six and seven times. 
In the other experiments, the cavities being much smaller,, 
the quantities of air and fluid could not be accurately mea- 
