20 



that the minerals were not of igneous origin, for if the water was 

 under pressure it might have been heated to a very high tempe- 

 rature without escaping. Indeed it is well known that water, 

 under artificial pressure, may be heated to redness without form- 

 ation of steam. 



Prof. Rogers expressed the opinion that changes upon the 

 strata resulted not so much from intrusive veins or dykes, as from 

 the gases and steam discharged during paroxysmal action. He 

 illustrated it by the phenomena exhibited all along the south-east 

 side of the Appalachian chain, especially in its extension through 

 Western Massachusetts and Vermont. The crystalline marbles 

 of Berkshire are only the older Appalachian Limestone, (the Ma- 

 tinal series of his nomenclature, the Chazy limestone of the New 

 York survey) in a metamorphic dress ; their fossils obscured or 

 effaced by crystallization. This view, long ago advocated by him, 

 has been confirmed by the discovery, by Mr. Hall and others, 

 of organic remains in the less altered portions of the same form- 

 ations in Rensselaer county, New York. The strata equivalent to 

 the Hudson river Slates are to be seen in the western ranges of 

 Berkshire, altered to the Talcose and Chloritic Schists. Locali- 

 ties were pointed out, where the Argillaceous rocks are to be 

 seen under the aspect of true Gneiss, and the so-called Vitreous 

 Quartz rock appears in the disintegrated condition of a soft 

 Sandstone. Through all this belt of country there is an almost 

 entire absence of veins or dykes. 



Prof. Rogers adverted to the progressive diminution of the 

 bitumen in the coals of the Appalachian chain, wherever we cross 

 the chain in the direction of northwest to southeast. This dimi- 

 nution reaches its maximum in Anthracites, to be met with only 

 along the south-east side of the belt ; where not only the coal, but 

 all the formations give evidence of igneous action. Yet here are 

 no traces of igneous, mineral injections. These facts have in- 

 duced him to refer the whole change to the agency of effluent 

 hot steam and gases, discharged during earthquake movements 

 that elevated the whole mountain chain. 



With respect to the presence of water in igneous minerals, he 

 remarked that we should view water in its elements as among 

 the essential constituents of the molten interior of the globe ; 45 

 per cent, of the whole fabric visible by man consisting of one of 

 those elements alone, viz. oxygen. 



