158 Account of (he Proceedings of the 



the component parts of serpentine, he observes, that if we infer that 

 all the basic water of serpentine is replaced by magnesia, we should 

 have the formula for olivine, so that we should expect these two mi- 

 neral substances to have the same crystalline form, which, adds M. 

 Scheerer, is the fact. This he considers as a proof of his new kind 

 of isomorphism, so that olivine is to serpentine what dichroite is to 

 aspasiolite. 



Taking this view, M. Scheerer calculates the proportion of oxygen 

 in more than one hundred minerals containing water, and examined 

 with care, and infers, that by considering this water as basic water, 

 the formulae become more simple, and more in accordance with the 

 composition furnished by chemical analysis, than when we consider 

 the water in a state of hydrate. From his researches, he concludes 

 that one atom of magnesia, or of protoxide of iron, manganese, co- 

 balt, nickel, and oxide of zinc, may be replaced in this kind of iso- 

 morphism, to which he assigns the name •polymeric, by thi-ee atoms 

 of water, and one atom of oxide of copper by two atoms of water.* 



Reasoning upon the water contained in many of the elements of 

 granite, in which he includes mica, iron pyrites, talc, hornblende, 

 schorl, gadolinite, orthite and allanite, M. Scheerer opposes the theory 

 of granite having been in a state of igneous fusion, though he does 

 not deny that heat may have given the humid mass of granite the 

 plasticity and softness which it cannot be denied it must have pos- 

 sessed, and thus he so far admits heat as having been an essential 

 agent in the formation of granite. He considers that this pasty mass, 

 impregnated with water, and heated under great pressure, would melt 

 at a tempei'ature much less elevated than if, in other respects the 

 same, it were anhydrous ; remarking that, from this fusion, which 

 should not be confounded with simply igneous fusion, results would 

 follow of a very different nature than if the mass cooled down from 

 igneous fusion alone. The minerals which had the greatest tendency 

 to crystallize, those of which the crystalline power was greater than 

 the opposing action of the watery vapours, would be the first to sepa- 

 rate. All the water, continues M. Scheerer, not appropriated by the 

 minerals during their crystallisation would be concentrated where the 

 free silica abounded. This silica would not become solidified until 

 late, when the temperature of the granite was considerably reduced, 

 and when the water not chemically combined with the component 

 minerals had escaped from the mass, a process requiring a long lapse 

 of time. M. Scheerer then applies this hypothesis to the alteration 

 of rocks brought into contact with the granite, plastic with water and 

 highly heated. 



* In thus giving this view of M. Scheerer, it is but right to observe that it 

 is opposed by Prof. Nauraann and Dr Kammelsberg, who consider that it re- 

 quires further proof. 



