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the igneous origin of those rocks. Next, a paper by M. Virlet 

 D'Aoust, who contends that Granite and Gneiss are the result of 

 a " normal metamorphism " of stratified Slates and Schists. A 

 third paper, by M. Achille Delesse, on the chemical and mineral- 

 ogical character of the unstratified crystalline rocks of the 

 Vosges, in which he arrives at the generalization, " that rocks of 

 the same age are of the same chemical and mineralogical con- 

 stitution ; and reciprocally that rocks of the same chemical and 

 mineralocrical constitution are of the same age." He enters into 

 a minute examination of the Felspars and other minerals of those 

 rocks, and considers that the water chemically combined in the 

 Felspars is inconsistent with the idea of their igneous origin. 



Mr. Teschemacher urged the importance of studying with 

 minuteness the mineralogical character of the boulders of this 

 country, before a proper comparison could be made between 

 them and the rocks in situ from which they are supposed to have 

 been separated. This he considered indispensable, before a true 

 judgment could be formed of the means by which, and the course 

 in which ihey had been moved. Mr. T. exhibited a ^Q\y speci- 

 mens in elucidation of his ideas. 



Mr. Desor remarked on the metamorphic character of the 

 crystalline rocks of the Alps, and the absence of Granite in those 

 mountains. What had been called such was undoubtedly trans- 

 formed sedimentary rocks. He had himself collected Belemnites 

 in the so-called Mica-slate of St. Gothard. 



Dr. Jackson said he had long been familiar with the altered or 

 metamorphosed rocks, and had minutely described them in his 

 State Geological Reports, particularly in that of Rhode Island, in 

 which he had described the alterations in the shales of the coal 

 measures. There may be seen, on the borders of the Rhode Isl- 

 and coal field, all the changes referred to ; and a mica-slate rock, 

 such as is used for scythe-stones, gradually passes into a slate and 

 sandstone rock of the coal measures. He had seen specimens 

 like those described in Mr. Teschemacher's communication. 



As to the existence of water in minerals, he would say that it 

 existed in most volcanic minerals, and in many of those from 

 the primary rocks, and must have been present at the time of 

 their formation. He did not regard its presence as any proof 



