44 Sir H. Davy on the State of Water and Aeriform [Jan. 



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 produced. 



Geologists are generally agreed that the greater number of the 

 crystalline inineral substances must have been previously 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. 



When, however, it is considered, that the solvent power of 

 water depends upon its temperature, and its deposition of s lid 

 matters upon its change of state or of temperature ; and that 

 being a gravitating substance, the same quantity must always 

 belong to the globe, it becomes difficult to allow much weight to 

 the arguments of the Wernerians or Neptunists, who have gene- 

 rally neglected, in their speculations, the laws of chemical 

 attraction. ' 



There are many circumstances, on the contrary, favourable to 

 that part of the views of the Huttonians or Plutonists, relating to 

 the cause of crystallization ; such as the form of the earth, that 

 of an oblate spheroid flattened at the poles ; the facility with 

 which heat, being a radiating substance, may be lost and dissi- 

 pated in free space ; and the observations which seem to show 

 the present existence of a high temperature in the interior of the 

 globe. 



1 have often, in the course of my chemical researches, looked 

 for facts or experiments, which might throw some light on this 

 interesting subject, but without success, till about three years 

 ago; when, in considering the state of the fluid and aeriform 

 matters included in certain crystals, it appeared to me, that 

 these curious phenomena might be examined in a manner to 

 afford some important arguments as to the causes of the forma- 

 tion of the crystal. 



It is well known that water, and all fluids at usual tempera- 

 tures, are more expansible by heat than siliceous or other earthy 

 matters ; and supposing these crystals to have been formed, and 

 the water or fluid enclosed in them, at a pressure and tempera- 

 ture not very unlike those of our existing atmosphere, this fluid 

 ought to fill nearly the same space as when included, and the 

 elastic fluid confined with it, supposing it non-absorbable, ought 

 to be in the same state of density. On the contrary, if the 

 earthy matter and the fluid separated from each other under a 

 much higher temperature than that now belonging to the sur- 

 face, a certain vacuum might be expected in the cavity from the 

 contraction of the fluid, and if any gas were present, a consider- 

 able rarefaction of it; and though, supposing a much higher 

 temperature on the surface of the globe, the atmosphere formed 

 by aqueous vapour must have had much greater absolute weight, 

 which, as liquids are compressible, must have influenced the 

 rolume of the fluid at the time it was enclosed, a circumstance 



