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XXVII. On the state of water and aeriform matter in cavities 
found in certain crystals . By Sir Humphry Davy, Bart. 
P. R. S. 
Read June 13, 1822. 
There are few enquiries in natural science more calculated 
to awaken our curiosity, than those relating to the changes 
which the matter composing the surface of our globe has 
undergone. The imagination is excited by the magnitude of 
the operations, by the obscurity of the phenomena, and the 
remoteness of the time at which they occurred ; and all the 
intellectual powers are required to be brought into activity 
to find facts or analogies, or to institute experiments, by which 
they may be referred to known causes. 
The crystallizations constituting the whole of the rocks 
which are usually called primary, and those found in such 
abundance, even in the rocks which are termed secondary, 
prove that a considerable part of the materials of the surface 
of the globe must have been either fluid or aeriform ; for 
these are the only states from which the regular arrangements 
of the molecules of bodies constituting crystals, can be pro- 
duced. 
Geologists are generally agreed, that the greater number 
of the crystalline mineral substances must have been pre- 
viously in a liquid state ; but different schools have supposed 
different causes for their solution ; some attributing this effect 
principally to the agency of water, others to that of heat. 
