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 plentifully occur 
wherever the rock is not covered by the drift, has somewhat disrupted 
the superficial 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 Hill 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 where 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 [V.). 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 
striee, 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 
