364 On the Geological Character of the Beds 



appear to have been derived from the primitive rocks. The 

 boulders are granite, gneiss, mica, schist, hornblende, and quartz. 

 The gravel stones are principally quartz. There are a few 

 rolled pieces of chert, old red sandstone, &c.; but their numbers 

 are so comparatively small, that their presence may be consider- 

 ed as accidental, and they can lay no claim to giving a general 

 character to a deposite which is manifestly diluvial in its origin. 



The boulders and gravel stones are partially rounded, indi- 

 cating that they have not been brought from a great distance, 

 and the nearest rocks in place are primitive. The felspar in the 

 granite boulders is a dull opaque white, and in a state of partial 

 decomposition. So it is in the neighbouring mica schist. Dr. H. 

 Hayden, author of the geological essays, is of opinion, that the 

 rolled pebbles of the diluvial districts of this country, lie generally 

 from three to five miles, and sometimes more, from their original 

 gangue, or locality. Guided by these considerations, we may 

 venture to pronounce the superficial deposite upon which Phila- 

 delphia stands, to be a " primitive diluvial." 



The next subject of inquiry is, by what means it was trans- 

 ported to where it is. The magnitude of the boulders, and the 

 immense quantity of diluvial matter, preclude the idea that they 

 have been brought by the Delaware and Schuylkill, even aided 

 by any freshes, judging from present appearances, with which 

 these rivers have ever been agitated. That a mighty current of 

 water has, at no very distant period, passed over this continent, in 

 a direction from N. and E. to S. and W., appears to be a fact 

 well proved. The able manner in which Dr. Hayden has ex- 

 amined this subject, precludes any discussion of it here ; I would, 

 however, remark, that when Coats street and Fair Mount street 

 were digging down to the regulation, I inspected the upper surface 

 p of the mica schist rock, as it was laid bare, and discovered furrows 

 upon it, all tending from N. E. to S. and W., as if something 

 hard or heavy had been dragged over it. This current was 

 probably consequent upon a flood of a general character, and to 

 which the diluvial matter owes its origin, being the comminuted 

 materials of the rocks it had torn and abraded. 



The materials of which this diluvial deposit is composed, are 

 now found, according to observation and the best information, in 

 the following order. 



1st A vegetable sod, or mould, which, where the ground is 



