180 REPORT— 1860. 



tible of a simple solution, and it is astonishing that chemists have not yet 

 carried their views in this direction. From the moment that we consider the 

 terrestrial globe as a mass of which the different parts have successively 

 undergone the action of fire, we must also conceive, as a necessary conse- 

 quence, a series of chemical phenomena, such as calcination, fusion, cemen- 

 tation, &c," meaning by this latter term, the mutual molecular inter- 

 penetration of bodies in contiguity, a process of which I shall presently have 

 to offer a remarkable example. 



There was one mineralogical chemist, however, of high eminence, who had 

 long before carried his views in the direction desired by Fournet. In 1823, 

 Mitscherlich, having examined the forms, and analysed the ingredients, of 

 forty crystalline products of furnaces*, to which Berthier had contributed 

 several parallel results of experimental processes, pronounced them identical 

 with various native minerals, and in particular with peridot, pyroxene, and 

 mica. In the artificial mica, however, he found lime, of which granitic 

 mica scarcely contains a trace ; and this led him to speculate on the cause 

 of the chief chemical distinction between the granite and trap formations, 

 consisting in the absence of calcareous and magnesian silicates from the 

 former. Supposing, he argued, that the primary rocks were formed at that 

 stage of the earth's refrigeration when -|ths of its water were in a state of 

 vapour, the pressure on every part of its surface, computed according to 

 Laplace's calculation of the mean depth of the sea, would be 225 atmo- 

 spheres f ; but under such a weight the affinity of lime for silica would cease ; 

 hence the crystals of uncombined silica in Carrara marble. 



The surmise has since been brought into evidence by an experiment of 

 Petzholdt, in which pulverized quartz, heated to whiteness with an equal 

 weight of carbonate of lime in an open vessel, was found to form a silicate 

 with the lime, but produced no combination when heated in a strong, close 

 vessel of iron. 



The crystallization of the primary rocks was supposed by the early Plutonic 

 theorists to be due to slow cooling; but this principle alone does not satisfy 

 the phenomena. The crystalline structure of granite is seen, for example in 

 Glen Tilt, at Shap Fell J, and elsewhere, to be equally uniform in its partial 

 irruptions into the superior strata, as where it appears to be the foundation 

 stone of the earth's crust ; it has crystallized in its accustomed manner, where 

 it has penetrated fissures of the upper beds in plates as thin as the leaves of 

 a book and threads as fine as a hair, and even where it is involved in the in- 

 vaded stratum so that no junction with any vein can be observed. How 

 could it have been thus injected in a state of fusion, unless of the most liquid 

 kind ? and how could the heat of such liquidity, in a material of which the 

 fusing-point is so high, be otherwise than rapidly cooled down? 



Furthermore, the quartz which forms so large a constituent of granite, 

 has always the specific gravity of crystalline silica, which exceeds that of any 

 other species of silica. But Deville and others have shown that fusion 



* Annales de Chimie, torn. xxiv. p. 258, 1824. Mitscherlich sur la production artificielle 

 des mineraux crystallises — "j'ai trouve, a Fahlun, du silicate et bisilicate de protoxide de 

 fer, a Garpenberg, du mica et du pyroxene, les memes figures crystallines, et tous les autres 

 caraeteres des mineraux correspondans, le bisilicate de protoxide de fer et de chaux, de 

 magnesie et de chaux, les trisilicates de chaux, de chaux et de manganese, le fer oxide (fer- 

 rosoferricum), le protoxide de cuivre, le deutoxide de cuivre, 1'oxide de zinc, les sulfures 

 de fer, de zinc, de plomb, l'arsenieure de nickel, &c. &c, et beaucoup d'autres substances 

 en cristaux bien prononcees. 



t In Mitscherlich's Memoire, as printed in the ' Annales de Chimie et de Physique,' 

 tome xxiv. pp. 372, 373, the atmospheres are stated as 2250, deduced from a mean depth of 

 sea, 9u,000 feet, with a cipher too much, that is, in both cases. 



\ I understand from Mr. Marshall that the ramified granite of Shap Fell is similarly 

 crystallized with the rest of the rock, but finer grained. 





