Intelligence and Miscellaneous Articles. 79 



7th of May, 1857*. I showed that solutions of alkaline carbonates 

 may give rise to the formation of silicates of lime, magnesia, and 

 protoxide of iron, when heated to 212° F. with mixtures of the car- 

 bonates of these bases with quartz, a silicate of the alkali being first 

 formed, and then decomposed by the earthy carbonates. Shortly 

 after, in my report of the Geological Survey for 1856, I suggested 

 that the alkaline silicates might combine with silicate of alumina to 

 form those felspathic and micaceous minerals which are so generally 

 associated with the silicates of protoxide bases ; I further suggested 

 that these minerals might be crystallized by the aid of heated alkaline 

 solutions under pressure, and I thus endeavoured to explain the 

 development of crystals of felspar and mica, in sedimentary rocks, 

 even where the organic remains are still preserved. 



While arranging an apparatus in which I proposed to heat under 

 pressure a solution of carbonate of potash with silica and kaolin, in 

 the hope of obtaining a double silicate of alumina and potash, M. 

 Daubree announced to the French Academy of Sciences (Comptes 

 Rendus, Nov. 16, 1857) that he had succeeded in obtaining cry- 

 stalline felspar, mixed with crystals of quartz, by heating during a 

 month, a mixture of kaolin and silicate of potash to 400° C. He 

 has moreover shown that felspars and pyroxenes are very stable in 

 presence of heated alkaline solutions, and that crystallized diopside 

 and WoUastonite are formed when artificial glasses, containing lime 

 and iron, are heated in the same way to 400° C. in the presence of 

 a small amount of water. The alkaline silicate which separates from 

 the decomposition of the glass is resolved into quartz, which forms 

 regular crystals, and a soluble silicate having the formula SiO, KO. 



These results of M. Daubree serve in the most remarkable manner 

 to confirm my theorj' of the normal metamorphism of sedimentary 

 rocks at temperatures below ignition, by the intervention of solutions 

 "of alkaline silicates, which convert mixtures of quartz and earthy 

 carbonates into the corresponding silicates, and clays into felspars 

 and mica, the intervention of alumina sometimes generating chlorite, 

 epidote and garnet. 



Daubree remarks that glass when thus heated in presence of water 

 swells up, indicating a softening and a plasticity of the mass ; and he 

 observes that his experiments enable us to understand the part which 

 water may have played in the formation of the igneous rocks. His 

 observations go far to support the views of Poulett Scrope and 

 Scheerer, who maintain the aqueo-igneous fusion of granites and 

 lavas, a theory which is further sustained by the curious micro- 

 scopical investigations of Mr. Sorby lately presented to the Geologi- 

 cal Society of London f. 



Sir John F. W. Herschel many years since put forward a theory 

 of volcanos, in which he suggested that all volcanic and plutonic 

 rocks were no other than sedimentary deposits, melted down with 

 their included water. 1 have endeavoured, in a paper read on the 

 6th of March before the Canadian Institute at Toronto, to show that 

 this theory is the one most in accordance with the present state of 



* Phil. Mag. vol. XV. p. 68. 

 t Ibid. p. 162. 



