410 PALEOZOIC TIME. 



Coal measures, the conglomerates and sandstones especially, are 

 often very hard and siliceous where the beds have been most folded 

 or disturbed. 



2. Dcbituminization of Coal. — The coal is without bitumen or a true 

 anthracite where the rocks are most disturbed; and going west- 

 ward, into regions of less disturbance, the proportion of bitumen or 

 volatile substances increases quite regularly (Rogers). It appears 

 as if the debituminization of the coal had taken place from some 

 cause connected with the uplifting. In Rhode Island the effects 

 are still more marked, the coal being altered not simply to an 

 excessively hard anthracite, but in part to graphite. 



3. Crystallization, or metamorphism. — In the regions where the folds 

 are pressed together most crowdedly and the evidences of disturb- 

 ance are extreme, as over New England, and the Eastern border 

 south of New York, the rocks are often crystallized, being granite, 

 gneiss, mica schist, and the like. There, also, granitic and mineral 

 veins abound. 



3. Some characteristics of the force engaged. 



The cause of this extensive series of flexures had, obviously, the 

 following among its characteristics : — 



1. The force acted at right angles to the course of the flexures, and, there- 

 fore, to the general direction of the Atlantic coast. — It is obvious, without 

 explanation, that only force from this direction could have pro- 

 duced the result. The process is easily imitated with paper or 

 cloth. 



2. The force acted from the direction of the ocean. — For all the effects — 

 the flexing and metamorphic — are most intense on the oceanic 

 side ; they fade out towards the interior. 



3. The force was vast in amount. 



If any one doubt, he may satisfy himself by working out the following 

 problem : — 



(a.) Given the thickness of the rocks at 30,000 to 40,000 feet (the depth 

 of the Palaeozoic in the Appalachians), part of the beds (if not all) already 

 stiff and solid, — for the limestones are as solid when first formed as ever after- 

 ward. (It is probable that the whole earth's crust was involved, giving a 

 thickness of 100,000 feet or more.) 



(b.) Length of region acted upon, 1500 miles; breadth, 100 to 300 miles. 



(c) Required to press the beds, over this region, from top to bottom, into a 

 series of great flexures such as has been described, and to force them on to the 

 northwest until the tops of many of the flexures shall overhang their bases to 

 the westward, and farther until numbers of them shall close up into a solid 

 body or mass : span of flexures, mostly from 1 mile to 50 : rise, mostly from 100 

 to 5000 feet. 



