174 Scientific Geology. 



when in a plastic state, it had been acted on by opposing lateral 

 forces. 



If I mistake not, this section throws light upon the manner in 

 which some of the disturbances in the older rocks may have been 

 produced. Let the stratum c, be only consolidated by heat, or other- 

 wise, and we have a perfect conglomerated sandstone, or gray wacke. 

 Let the stratum d, be not only consolidated, but partially melted, so 

 as to become in a good degree crystalline ; and we have that variety 

 of mica slate or quartz rock, in which the planes of stratification do 

 not correspond with the contorted schistose layers. The undisturbed 

 beds of sand, by the same igneous action, might be converted into 

 quartz rock, or mica slate ; and the interlaminated layers of clay, 

 into argillaceous slate, or hornblende schist, or both. Thus from 

 this thin tertiary formation, might result hornblende slate, mica slate, 

 quartz rock, argillaceous slate, conglomerated gray wacke, and sand- 

 stone : and these might present much of the regularity and irregu- 

 larity, peculiar to each rock. And to accomplish all this, and also 

 to give the strata an inclined position, we have only to suppose the 

 the same volcanic agency to be exerted, which we know has been a 

 thousand times employed in the elevation of strata, and in the pro- 

 trusion of the unstratified rocks. 



,pA^k^A^i>x.A^A^ 



b ~ a 



- 



a 



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Section of a Cliff of Tertiary Clay and Sand : Deerfield. 



