126 Horner's Geological Address. 



years ago, any geologist would have termed primary, but 

 which are, in fact, only altered palaeozoic sedimentary strata. 

 If we cross the Atlantic to North America, we obtain equally 

 clear proofs of the alteration of the sand and mud of the lands 

 of remote antiquity into crystalline schists, and of the forests 

 that grew upon them into anthracitic coal, by this same power- 

 ful agency. 



The Appalachian or Alleghany mountains, which run from 

 north- north-east to south -south-west for 1000 miles, varying 

 in breadth from 50 to 150, and in height from 2000 to 6000 

 feet, have not, like the Ural chain, the features of a great rent 

 in the earth's crust formed by elastic forces from beneath, 

 and into which molten rocks were injected ; they are com- 

 posed of Silurian, Devonian, and carboniferous rocks, in a 

 series of nearly equal and parallel ridges formed by flexures 

 of these rocks. The bending and fracture of the beds is 

 greatest on the north-eastern or Atlantic side of the chain, 

 and the strata become less and less disturbed as they extend 

 westward, until at length they regain their original or hori- 

 zontal position ; thus offering between the Alleghanies and 

 the western boundary of the basin of the Mississippi, a coun- 

 try very similar in conformation to that between the Urals 

 and the Baltic, and composed, to a great extent, of similar 

 rocks. The internal movements which caused these flexures 

 took place, as in Russia, subsequent to the carboniferous 

 period ; and on the eastern side the igneous rocks have in- 

 vaded the strata, forming dykes, some of which run for miles 

 parallel to the main direction of the mountains. These igne- 

 ous rocks are largely developed to the north-east in the States 

 of New Hampshire, Vermont, and Maine. 



Near Worcester in Massachusetts, Mr Lyell observed mica- 

 schist containing beds of anthracite, the mica-schist includ- 

 ing garnets and asbestus ; and he states that he is strongly 

 inclined to believe, that however crystalline they may be, they 

 are no other than carboniferous rocks in a metamorphic state. 

 There are many other places in Rhode Island and Massa- 

 chusetts of similar transformations, especially in the neigh- 

 bourhood of masses of granite and syenite.* The coal, which, 



■* Ly ell's Ameriru, vol. i. p. 248, 



