174 R. D. SALISBURY EXTRA-MORAIXIC DRIFT. 



moraines would be found toward the north equivalent to those of the 

 interior, and referred to a later ice epoch. Subsequently, whenglaeialists 

 familiar with the phenomena of older and younger drift sheets as devel- 

 oped in the interior came to study the drift of the states in question, the 

 terminal moraines of New Jersey and Pennsylvania and the drift north 

 of it were found to correspond in all essential points with the later glacial 

 drift of the interior instead of with the earlier. 



Still proceeding on the belief that the moraine represented the southern 

 limit of the drift, it was inferred that the ice-advance of the later glacial 

 times was equal to or exceeded that of the earlier, and that therefore the 

 deposit of the latter was overridden and obliterated or obscured by the 

 former. This interpretation, however, has never seemed entirely har- 

 monious with the accepted interpretation of the drift phenomena of the 

 interior. President Chamberlin has more than once expressed the 

 opinion, though he has nowhere published it, that there might be an 

 older drift sheet south of the moraine in New Jersey and Pennsylvania 

 which had escaped observation. Two years since, with this suggestion 

 in mind, though primarily for another purpose, President Chamberlin 

 and the writer made a cursory examination of certain extra-morainic 

 areas in New Jersey and Pennsylvania. The result of this examination 

 was to strengthen the suspicion that glacial drift did not find its southern- 

 most limit in New Jersey and Pennsylvania along the line of the moraine. 



The phenomena which were then observed have never been published. 

 The most significant fact developed was the existence of glacially striated 

 stony material many miles south of the moraine at one point at least in 

 New Jersey and at three points in Pennsylvania. The striated stones 

 were occasionally seen to be embedded in a matrix of clayey nature, re- 

 sembling till. This bowldery clay was of such a character and in such 

 positions as to make the suggestion of its derivation from the moraine 

 toward the north unsatisfactory if not altogether untenable. Some of 

 the phenomena seen were capable of explanation without supposing 

 glacier ice to have been present in the region where they occur: others 

 seemed to us to find their most rational explanation in the supposition 

 that glaciation had extended beyond the limit hitherto assigned it. 



In June of the present year the writer visited New Jersey, and then 

 learned for the first time that Professor Smock had long entertained the 

 idea that there might be a formation of glacial drift south of the moraine 

 which he had traced across the state. Professor Smock was in possession 

 of a number of facts concerning the character of the surface formation 

 south of the moraine which afforded sufficient basis for the idea which 

 he entertained. When the writer undertook the detailed study of the 

 Pleistocene formations of New Jersey a little later in the season, 1'rol'essor 



