37 * 
Sz'r Humphry Davy on the state of water 
yet many occurred, in which the sides of the cavity were abso- 
lutely impervious to air or water. 
The results that I obtained were very analogous. Water 
containing very minute quantities of saline impregnations, 
occasioning barely a visible cloudiness in solutions of silver 
and of muriate of baryta, was found to be the fluid ; the gas 
was azote, but it was in a much more rarefied state than in 
the rock crystals, being between 60 and 70 times as rare as 
atmospheric air. 
The quantity of water was to the void space in greater 
proportion than in the rock crystals. In the instance in which 
the most accurate experiment was made, namely, on the 
great specimen preserved in the collection of the British 
Museum, and which weighed 380 grains, the quantity of 
water was 29.9 grains, the space occupied by aeriform matter 
was equal to 11.7 grains of water, the volume of the globule 
of gas at the common pressure was to that of its rarefied 
volume as 1 to 63. 
It occurred to me that atmospheric air might have been 
originally the elastic fluid included in these siliceous stones 
and in the crystals, and that the oxygene might have been 
separated from the azote by the attraction of the water, and 
a direct experiment seemed to confirm this idea. A chalcedony 
which had been bored was placed in water free from air under 
a receiver, which was exhausted till a portion of gas from the 
interior of the crystal had escaped into a proper receptacle. 
This gas examined by nitrous gas, was found to contain nearly 
as much oxygene as atmospheric air; so that there is every 
reason to believe that the water had emitted oxygene during 
the exhaustion. 
