270 



TRANSACTIONS OF THE 



arctic sea, has been variously accounted for by theoreti- 

 cal writers: but the hypothesis of a central heat is advo- 

 cated by many geologists ; and Mr Lyell has proved that 

 a certain distribution of sea and land would go far to 

 produce the temperature which must have existed in the 

 carboniferous era. Others, however, deny its efiiciency 

 to produce so vast a difference, and call in the aid of 

 central heat. It seems certain that volcanic eruptions 

 were very frequent and widely distributed in the epoch 

 in question ; and the identity of organic remains, so re- 

 markable in the grauwacke wherever it occurs, proves 

 that the disturbing forces acted throughout many parts 

 of our globe in a single geological era. The lavas being 

 almost uniformly poured into the bed of the sea, must 

 have greatly elevated its temperature. And who can cal- 

 culate to what extent thermal springs may have modified 

 the temperature of the shallower seas which encircled 

 the volcanic isles ? 



Here, as in Europe, we find, in the strata overlying 

 the coal, ferns and fucoides, marine and fresh water 

 shells, and all the phenomena which tend to prove the 

 existence of a vast ocean, interspersed with many islands ; 

 and we cannot but cherish the hope that an accurate in- 

 vestigation of the fossils will at some future day explain 

 the origin of our beds of anthracite and bituminous coal, 

 or at least exhibit the state of the earth^s surface in that 

 interesting period in which they originated. 



I have ascertained that the extreme southern limit of 

 the grauwacke group, east of the Mississippi, is at the 

 town of Tuscaloosa, in Alabama; sandstone here forms 

 the bed of the Black Warrior river, and it is remarkable 

 that small masses of bituminous coal are imbedded in it 

 in such a manner as to show clearly that they originally 

 fell upon a very soft and yielding surface. Whether 

 this sandstone is the result of deposition or of igneous 

 fusion, I leave for others to decide. 



