GEOLOGY OF THE VICINITY OF LITTLE FALLS 61 



deposition was taking place, indicating a slope of nearly 30 feet 

 to the mile. 



From Middleville to Ilion, in the opposite direction, the distance 

 is 9 miles. The Beekmantown thickens 275 feet in the distance, 

 from 200 to 475 feet, or again 30 feet to the mile. 



From Little Falls northward to the spot of Beekmantown dis- 

 appearance the distance is 15 miles. The Beekmantown rocks at 

 Little Falls are 450 feet in thickness. This wholly disappears in 

 the 15 miles, indicating again a slope of 30 feet to the mile. 



The two latter measurements are both made in a nearly south- 

 erly direction and agree very closely. The first measurement is 

 made in a southwesterly direction and falls somewhat short of the 

 other two, which would indicate that the general slope of the sur- 

 face was to the south. It is not meant to imply that this slope 

 was maintained over any great distance, nor that it was uniform 

 throughout, nor does it follow that the whole thickening to the 

 south is due to overlap. But the figures do seem to demonstrate 

 a southerly sloping sea floor, whose rate of slope was not over 30 

 feet to the mile, though it may have been somewhat less than that, 

 and which is at least maintained throughout the area covered by 

 the map. 



As will be immediately shown there was some disturbance of the 

 district during the early Trenton which must have affected this 

 slope both in direction and in amount. Unfortunately also no 

 quantitative data for determining the amount of this effect are at 

 hand. But the effect could not have been great. If we assume 

 that the effect was nil, and allow the Trenton rocks a thickness of 

 300 feet, which is close to their maximum hereabouts, then they 

 would have only reached in 10 miles farther on the old surface 

 than the Beekmantown rocks do, if the same rate of slope was 

 maintained, beyond which the Utica would have overlapped on the 

 surface. Nor would the Utica and Lorraine shales of the Hudson 

 formation have extended in mor.e than 30 miles farther over the 

 region, even on the assumption that they were deposited to their 

 full thickness, which is not likely. This line of evidence would 

 therefore, so far as it may be worth anything, seem to indicate that 



