Shi.lur.] 248 [March 7, 
exist along tlie shore, destroying or modifying the relief in a 
manner which can be interpreted long after the occnrrence of the 
catastrophe. It appears to me i)Ossible by a careful study of most 
shores to determine whether they have recently been subject to 
inundations of this nature. Thus far I have been able to apply 
the method of inquiry only to the coast of the United States 
between Eastport and Key West. I shall give the general results 
of the inquiry on this extensive shore section in order at once to 
show the method in which it can be used and the evidence con- 
cerning earthquake shocks beneath the Atlantic floor during the 
period which has elapsed since the eastern coast line of the United 
States came to its present position. 
Between Eastport and the mouth of the Hudson, the evidence 
concerning these oceanic waves, though complicated, is of a very 
legible nature. On this shore the facts which afford us ififorma- 
tion ai-e those which owe their existence to glacial action. 
Along the rocky part of this coast, we have a great number of 
poised boulders, erratics which were left in their position by the 
melting away of the glacier, and which lie in attitudes where 
eitlier a considerable shock occurring beneath them or the incom- 
ing of a great wave would inevitably lead to their displacement. 
In my examination of this shore, the greater portion of which I 
have actually seen either on foot or from a small boat, 1 have 
found many hundred boulders delicately poised in positions where 
tlie blow of a great wave would lead to their overturning. We 
often find the boulders slightly supported on the margins of steep 
declivities just above the present range of the waves so that any- 
thing but the most trifling disturbance would cause them to be 
precipitated down the slope. Although in some instances it is 
possible to suppose that vegetation, the roots of trees and their 
stems, may at one time have served in a measure to fix them in 
their resting places, there are many other cases in which we can 
aflftrm that the instability of their attitude must have continued for 
all the time since the shore came to its present level. 
At other points along these rocky shores, especially on the 
coast of Maine, as on Baker's Island south of Mt. Desert, the 
ocean waves have heaped up a sea-wall composed of angular 
fragments torn from the jointed crystalline rocks. An inspection 
of the stones composing these walls shows that most of the frag- 
ments have long been in their present positions, and also that they 
