134 ACCOUNT OF THE 



porphyry^ trap, jasper, petrosilex, Jlmt, agate, quartz, and 

 various other ancient species. These are ot every size from 

 small gravel to boulders fit for street and court paving. They 

 are not angular, but have suffered attrition, until the distinc- 

 tive characters of many fragments are almost obliterated, 

 and a fracture must be made before they can be known. 

 They are blended intimately with the other stoney wreck, 

 and have not hitherto been found to occupy any distinct 

 bed. The source of this debris of primitive and transition 

 strata can be best ascertained by tracing its distribution over 

 the country. 1 have observed pebbles of this kind on the 

 Hudson river at West Point, where the plain is composed in 

 part of rolled fragments. But as they are in general larger 

 than those found on the Ohio, less worn and polished, have a 

 greater proportion of mica slate pebbles, which do not seem 

 to bear rolling to a great distance, and are mixed with rub- 

 ble from the sand stone mountains of Katskill, they should, 

 1 think, be considered as being detached from the adjacent 

 primitive rocks. An additional reason for this opinion may 

 be drawn from the silence of our excellent friend Professor 

 Mitchill as to the debris of ancient strata among the alluvion 

 of the upper parts of the valley of this river.* It seems 

 probable then that the currents whicli rolled and polished 

 these fragments, did not extend laterally as far as the basin 

 of the Hudson. We do not however depart from it west- 

 wardly but a short distance, before we meet with the ruins 

 of primitive strata. An observing traveller, Mr. J. C. War- 

 ren, informs me that he saw them on the Chenongo, a branch 

 of the Susquehanna, and observed them near all the streams 

 in passing thence by the town of Erie on the lake, and along 

 the Allegheny river to Pittsburg. Mr. Thomas Nuttall had 

 previously noted the same thing during a joumey in which 

 he visited most of the principal rivers and lakes in the west- 

 ern part of New York. So much for the north-east. To 

 the south-east and south, the valley of the Ohio seems to 



* See Medical Repository, Vol. I. 



