GEOLOGY OF THE VICINITY OF LITTLE FALLS 67 



the yet more even surface on which the Paleozoic rocks were laid 

 down. The evidence is in brief as follows : 



Examination of the Little Falls topographic sheet shows a pro- 

 gressive rise of the pre-Oambrian hilltops going northward, the 

 highest elevations reached being somewhat over 2000 feet. On 

 the Wilmurt sheet (lying directly north of the Little Falls sheet) 

 the same fairly concordant altitudes are to be noted, and the 

 same slow increase northward, the higher summits in the northern 

 part of that sheet showing elevations slightly over 2500 feet. 

 This is an increase of about 500 feet in 18 miles, or between 25 

 and 30 feet to the mile. Northward along the western edge of 

 the same sheet the rise is somewhat more rapid, about 50 feet to 

 the mile. 



Some idea of the general slope of the pre-Cambrian surface 

 underneath the Paleozoic rocks may be obtained by comparing 

 the altitudes of this surface at Little Falls and at Diamond hill 

 for one line, and from Ilion through Middleville and thence north- 

 ward for another line. 



Diamond hill is 8 miles north of Little Falls. The Spruce 

 creek contact there is at 1200 feet altitude. The pre-Cambrian 

 in the river above little Falls, taken at that point in order to 

 avoid the lifting effect of the fault as much as possible, is at 400 

 feet. Thus there is a rise of the pre-Cambrian surface of 800 

 feet in the 8 miles, or 100 feet to the mile. Since Diamond hill 

 is farther away from the upthrow influence of the fault, this 

 amount is probably a little too small. 



In the well at Ilion the pre-Cambrian was reached at 1105 feet, 

 or 700 feet below sea level. At Middleville it is 500 feet above 

 tide, a rise of 1200 feet in between 9 and 10 miles, or about 130 

 feet to the mile. Ten miles north of Middleville the pre-Cambrian 

 appears from under the Trenton at 1300 feet altitude, a rise of 80 

 feet to the mile. 



While these results are not particularly concordant, and while 

 more data are much to be desired, they do seem to indicate that 

 the one surface falls to the south more rapidly than the other, 

 say from two to three times as rapidly. Both surfaces fall also 



