INTRODUCTION. «! 



Sir William Logan has obtained from strata of this age, in Gaspe, frag- 

 ments of the trunk of a tree several inches in diameter; and the 

 abundant distribution of plants in that region indicates a proxilnity to 

 their source, or that they are now imbedded in the soil where they gi-ew. 



In the Coal measures proper, we find a similar state of things, with 

 the mass of material much greater, the remains of a former flora 

 extremely abundant and widely diffused, and the indications still 

 stronger that, to a great extent, the area occupied by these strata was 

 the land on which the plants flourished ; that they were destroyed by 

 Buccessive inundations or submergences, when the overflow of the 

 waters bore with them the coarser materials which covered the pre- 

 existing flora. 



In Nova-Scotia, with the profusion of land plants, there occur also 

 remains of land shells : in Pennsylvania, and nearly all the more easterly 

 Coal measures, land plants are abundant. 



These conditions, however, whatever they may have been, declined 

 towards the west. The shore-derived material has extended only partially 

 over the area ; and there is in that direction not only a thinning of the 

 entire mass, but also a paucity of plant remains. 



There is, moreover, a large accession of calcareous matter in that direc- 

 tion. On comparing the sections of Professor Swallow, which are given in 

 great detail, we find everywherje, but more particularly in the two upper 

 divisions, a large proportion of calcareous material in the form of argilla- 

 ceous shale, marl, etc., with numerous marine shells. The same is true of 

 the Coal measures in the west : in Iowa, Illinois, and Indiana, we find an 

 approach to this character. In Pennsylvania calcareous bands are few, and 

 in extremely small proportion, increasing in Ohio and the west; while in 

 Nova-Scotia, calcareous beds form a very insignificant proportion of the 

 whole. 



This condition is only to be explained by supposing, as we have more- 

 over evidence in proof, that the Coal measure sediments were driven 

 westward into an ocean wliere there already existed a well marked marine 

 fauna. This part of the ocean bed was subject to oscillations, and at times 



