PALiEONTOLOGY OP NEW-YORK. 



If the quantity of siliceous and aluminous ingredients brought up by such springs were 

 great, instead of being utterly insignificant, it might be contended that the mineral matter 

 thus expelled implies simply the decomposition of ordinary subterranean rocks ; but the 

 prodigious excess of carbonate of lime over every other element must, in the course of time, 

 cause the crust of the earth below to be almost entirely deprived of its calcareous consti- 

 tuents, while we know that the same action imparts to newer deposits, ever forming in seas 

 and lakes, an excess of carbonate of lime. Calcareous matter is poured into these lakes and 

 the ocean by a thousand springs and rivers; so that part of almost every new calcareous 

 rock chemically precipitated, and of many reefs of shelly and coralline stone, must be de- 

 rived from mineral matter subtracted by plutonic agency, and driven up by gas and steam 

 from fused and heated rocks in the bowels of the earth. 



Not only carbonate of lime, but also free carbonic acid gas is given off plentifully from 

 the soil and crevices of rocks in regions of active and spent volcanoes, as near Naples and 

 in Auvergne. By this process, fossil shells or corals may often lose their carbonic acid, and 

 the residual lime may enter into the composition of augite, hornblende, garnet, and other 

 hypogene minerals. That the removal of the calcareous matter of fossil shells is of frequent 

 occurrence, is proved by the fact of such organic remains being often replaced by silex* or 

 other minerals, and sometimes by the space once occupied by the fossil being left empty or 

 only marked by a faint impression. We ought not indeed to marvel at the general absence 

 of organic remains from the crystalline strata, when we bear in mind how often fossils are 

 obliterated, wholly or in part, even in tertiary formations ; how often vast masses of sand- 

 stone and shale, of difiFerent ages and thousands of feet thick, are devoid of fossils ; how 

 certain strata may first have been deprived of a portion of their fossils when they became 

 semi-crystalline, or assumed the transition state of Werner, and how the remaining 

 portion may have been effaced when they were rendered metamorphic. Rocks of the last- 

 mentioned class, moreover, have sometimes been exposed again and again to renewed 

 plutonic action." 



It appears tq me tliat the facts I have adduced regarding the distribution of 

 sedimentary materials, as exhibited in tlie eastern part of the United States, 

 offer a clear and simple solution of this question. Indeed it only requires that we 

 consider the origin and mode pf distribution of the sediments and the accumulation 

 of calcareous beds, whix^h together form the crust of the globe, to discover the 

 impossibility of having an equal or approximatingly equal amount of calcareous 

 matter among the metamorphic rocks. It is only in the regions of great accumula- 

 tions of transported sedimentary matter that the conditions of metamorphisra 

 exist, or at least operate on an extensive scale. The conditions under which these 

 fipposits were made, did not admit of large accumulations of calcareous matter; 

 and I have shown that in relation to the Appalachians, the greater amount of 



* [ This happens quite as often in the non-metamorphic as in the metamorphic strata. H.] 



