192 BULLETIN OF THE 



to isolated masses of hard, homogeneous rock which has been worn 

 by glacial action. At the close of the Glacial Period this region prob- 

 ably was for a time below the level of the sea, and during the re- 

 elevation of the land the surface of the hill appears to have been exposed 

 to the washing action of the waves, by which the covering of drift mate- 

 rials was in good part removed from its summit and accumulated about 

 the base of the elevation. The slightly undercut cliffs on the eastern 

 face of the mass may likewise be due to wave action. The expansive 

 effect of frost acting in the frequent open joints, which plentifull}' occur 

 wherever the rock is not covered by the drift, has somewhat disrupted 

 the supei'ficial portions of the mass. Notwithstanding these natural 

 and artificial changes, the elevation still retains the general aspect which 

 it had at the close of the Glacial Period. It has probably not, on the 

 average, lost more than six inches in depth of material since the ice 

 passed away. 



In the details of its structure the iron ore which constitutes the Cum- 

 berland Hdl is remarkably uniform. There are relatively few joints, 

 and these, except in the upper parts of the hill, are usually latent ; 

 that is, they are generally developed only wdiere the rock is subjected to 

 a considerable rending force. At one place on the western side of the 

 hill, near its northern end, there was until recently a large surface of 

 rock exposed by the artificial removal of the drift, preparatory to quarry- 

 ing work. This surface, containing an area of about five hundred square 

 feet, was in precisely the condition in which it was left at the close of 

 the Glacial Period. The finest scratches made by the moving ice were 

 not in the least effaced (see Plate IV.). From this and the other small 

 and imperfectly preserved glaciated exposures which the hill affords, I 

 have sought to determine the nature and measure of the ice action on its 

 mass. Of the several possible problems, two were selected for discus- 

 sion ; first, as to the direction of movement of ice over the surface of 

 the hill ; and secondly, the proportionate amount of wearing done by 

 the plucking out of fragments and by the rubbing down of the surface. 



The data for determining the general direction of the ice movement in 

 the region to the north and west of this district are imperfect, for the 

 reason that the rock is not of a nature to have formed or retained glacial 

 8tri£e, and is generally covered with glacial detritus. The scattered ob- 

 servations which are obtainable, serve to show that the average move- 

 ment was the same as that which is indicated by the central line of the 

 boulder train. When, however, we study the scratches exhibited on this 

 hill, especially those which occur on the large artificially exposed area 



