REPORT ON THK GEOLOGY OF NORTH AMERICA. 15 



lying strata to the greatest depth. Over the whole of this ex- 

 tensive territory it covers the horizontal strata of the tertiary 

 and cretaceous deposits, and obscures them so effectually that, 

 except in the cliffs, along the rivers, and in the sides of the ra- 

 vines and valleys, these formations are rarely or never exposed. 

 If we begin our examination of this great mass of detritus 

 upon the Atlantic coast, we there find it to consist of fine sand 

 and gravel, in which form it abounds over the peninsula of 

 Jersey, Maryland, Virginia, and North Carolina, and all the 

 states along the Atlantic to the Mississippi. This soil along 

 the seaboard may very possibly, if we judge from its consisting 

 so entirely of pure finely comminuted sand, have been reclaimed 

 from the ocean since the general distribution of diluvial matter 

 over the continent. But even upon this view, it is to be re- 

 garded as the result of diluvial action. The pebbles are of a 

 kind, in fact, which could only come from the interior, above 

 the range of rocks bordering the tide. They do not belong to 

 the tertiary and cretaceous strata of the Atlantic plain, but to 

 the older rocks of the Atlantic slope and the mountains. As we 

 advance inward from the coast, the mass of diluvial matter be- 

 comes less sandy and coarser, the soil somewhat less barren, 

 and the vegetation more diversified, though still consisting 

 principally of pine. Over the upper portion of the Atlantic 

 plain, or nearest its rocky boundary, the mass contains the 

 gravel in a much coarser state, mingled with clay sufficiently 

 pure for bricks. Rolled blocks and boulders of no inconsiderable 

 size occur, especially in the valleys of the rivers, when within 

 ten or twelve miles of the boundary mentioned. For many miles 

 from the coast there is rarely anything but the diluvium. In 

 the central districts of the tract the fossiliferous strata appear 

 beneath it, though near the upper limits of this tract these 

 often disappear again, and the region immediately eastward of 

 the rocky boundary presents the diluvium covering another class 

 of deposits very different from the tertiary and secondary beds 

 which underlie it near the sea. 



The deposit along the east of the rocky boundary, or, in other 

 words, at the head of tide hi the Middle States, is not diluvium, 

 as from the absence of fossils many might at first imagine. At 

 many places, as Bordentown on the Delaware, the deep cut of 

 the Chesapeake and Delaware Canal, Baltimore, &c., the mingled 

 mass of ordinary diluvium reposes upon very regularly stratified 

 beds of dark blue clay, containing decayed trees, lignite, and 

 amber ; the whole mass precisely such in appearance and con- 

 tents as to lead to the conviction that it is more probably an al- 



