8 PROCEEDINGS OF MADISON MEETING. 



During the present season I have had the opportunity of extending observations 

 eastward and southward. The additional facts now presented sustain most of the 

 conchisions of the previous paper, but modify some, and, as I trust, will be found 

 an advance in the endeavor to locate the southern limit of the earlier extension of 

 the ice-sheet. A part of this field-work this year, as last, was done in company 

 with Professor G. F. Wright. 



Character of the glacial Material. 



The area south of the moraine presents great geologic and topographic diversity, 

 and as a result -the glacial deposits in this area exhibit a great variety both as to 

 their lithologic constitution and as to their structural arrangement. Lithologically 

 we have in place Hudson river slates and shales, Siluro- Cambrian limestones, 

 Cambrian quartzites and Archean gneisses, which, although they exist also in the 

 regions north of the moraine, are found in place south of the moraine and enter 

 conspicuously into the extramorainic deposits. Beyond these we find the south- 

 ernmost glacial deposits spread out upon the red Triassic formation, and in such 

 cases the Trias has contributed richly of its varied elements — shales, sandstones and 

 quartzites ; the latter from its conglomeratic layers. For foreign elements we find 

 bowlders representing the Oriskany, the Clinton, the Medina and Oneida, all of 

 which exist in place in the region of Kittatinny mountain, upon the extreme 

 northern border of the state, while the Green Pond mountain series lies at a less 

 distance north of the moraine. Doubtless, also, some of the erratics are to be 

 ascribed to the Laurentian area of the north. While all of these elements may 

 enter into the composition of a deposit, it is still by the recognition of the few that 

 may be scattered upon the surface of a region that the path of the ice is principally 

 traced. 



Topography of the Region and its Influence on Glaciation. 



The topography of the region also is sufficiently varied to beget great diversity 

 in the thickness and extent of the true glacial deposits. On the west there are 

 highland ridges which run diagonally to the principal direction of ice-flow, thus 

 deflecting the ice-currents and affecting the position and the thickness of the 

 deposits. Further east there are several trap-ridges which similarly affected and 

 limited the ice-flow. Even the smaller preglacial valleys of erosion, which consti- 

 tuted the finer features of the surface configuration, are sometimes seen to have 

 controlled the local thickness of deposits, while postglacial erosion, however great 

 or small this may be, has added its effect in the same direction. This great variety 

 of aspects which the drift presents, while it adds interest to the task, adds also 

 some difficulties which are not everywhere encountered, with a resulting variety 

 of views on the part of different observers. 



Determination of the boundary Line. 



The region where the limit of the ice-flow can be most distinctly seen is perhaps 

 neither on the eastern nor on the western border of the state, but nearer the cen- 

 ter. Over the tolerably level plain west of Somerville and south of White House, 

 where the rock in place is a rather uniform Triassic shale, there are several points 

 where the distribution of northern material ceases abruptly. One of the most 



