430 NEW YORK STATE MUSEUM 
vestigation. In connection with a brief description of the Alta- 
mont well (already mentioned) he says, “If the geologist follows. 
along the contact of the Hudson series with the Lower Helderberg 
to the Schoharie kill and then proceeds down stream to the valley 
of the Mohawk he will pass over a large portion of the sectioné 
penetrated by the well, and in the valley of the Mohawk find that 
the series rests conformably upon the ee Hane stom, and that 
the base is formed of dark Utica shales.” 
Topography - 
Topographically the area under consideration may be divided 
into three regions accurately corresponding to as many types of 
geologic formations. These regions are 1) thé limestone region 
comprising all the area of the outcrop of the Calciferous-Trenton 
formations; 2) the region of the outcrop of the Utica shale and 
3) the region of the outcrop of the Hudson river shales and sand- 
stones. Besides these there are slight modifications of the typical 
topography of these formations due to glacial drift: 
The first region, that of limestone, is characterized by a low raline 
relief and shallow stream valleys, except where the streams have 
been forced to cut new courses through morainic: material or 
because of the obstruction offered by such material have been 
turned aside to make new rock cuts. The latter is probably the 
case with the lower courses at least of the North Chuctanunda and 
Evakill, for while they are at present making rock cuts their 
banks show deep cuts through boulder clay and their beds are in 
no respect those of mature streams, both from the abundance of 
waterfalls and the irregularity of their slope. The northwestern 
portion of this region is heavily covered with drift and the topog- 
raphy is more angular on this account. 
Along the eastern border of the limestone belt the topographic 
features are determined by the presence of the Hoffman ferry 
fault, and along most of this line there is a distinct escarpment as 
described in another part of the present paper. At its northern 
end this escarpment is dissected, leaving only a number of isolated 
hills with their longer axes in a northeast-southwest direction. The 
southern end however stands out in a bold cliff just back of Hoff- 
1Geol. soc. Amer. bul, Ap. 1890, 1:346, 
