PETROGRAPHY. 353 



line schists, in common with most of the older massive rocks, 

 by the agency of water, without the aid either of pressure or of 

 increased temperature. During the years 1826-28, Studer and 

 Elie de Beaumont made the observation in the Swiss and 

 Savoy Alps that gneiss and micaceous schists repose upon 

 unaltered sedimentary strata, and that in certain crystalline 

 schists fossils are present which prove them to belong to 

 relatively young geological epochs. This discovery was a very 

 great blow to the geologists who upheld the hypothesis of the 

 Archaean or pre-Cambrian age of all gneisses and schists. 

 Studer suggested some time later (1855) that the transforma- 

 tion of these schists had proceeded not outward from the lower 

 horizons to the upper, but possibly inward from younger and 

 outer horizons of rock to deeper crust-levels. Hoffmann, who had 

 in 1830 observed crystalline schists interbedded with conglomer- 

 ates and coarse grits of the "transitional" series, advocated the 

 view that the stratified grits and conglomerates represented un- 

 altered patches, and the gneiss and schists represented altered 

 portions of one and the same geological formation. 



Lyell accepted the Huttonian hypothesis in its essential 

 features, and the wide circulation of his principles gave 

 Mutton's teaching greater currency abroad. In addition to 

 heat and pressure, Lyell thought electrical and other agencies 

 might have combined to render the sedimentary structures 

 semi-fluid, the rock material having then been re-arranged ; 

 traces of organisms disappeared, but the bedding-planes for 

 the most part persisted. Lyeli taught that gneiss and micaceous 

 schist represented sandstones which had been altered by contact 

 with eruptive rocks, argillaceous schists had been originally 

 shales, and marble represented limestone that had been 

 rendered crystalline. In accordance with the Huttonian 

 doctrine that the high temperature had acted outward through 

 the crust, the lowest schists and gneisses were said by Lyell 

 to be those which had suffered the greatest degree of meta- 

 morphism. At the same time, under certain circumstances 

 comparatively young deposits might be metamorphosed, and it 

 could by no means be assumed that all crystalline schists must 

 belong to the fundamental or Archaean rocks. It was Sir 

 Charles Lyell who gave to the group of gneiss and crystalline 

 schists the name of " metamorphic " rock, and the name was 

 rapidly adopted in the special literature of geology and in 

 text-books. 



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