President's Address. 3 
under the sea during the course of geological time, while 
parts, at any rate, of the areas now occupied by the ocean 
have been in the condition of dry land. 
It is not necessary to discuss here whether the repeated 
submergences of the dry lands above referred to are the 
result of differential movements of elevation and depression 
in the earth’s crust, or whether they may not be due in part 
to local alterations in the level of the ocean, as believed by 
Neumayr. The repeated occurrence of such submergences 
as a primary fact in geological history, is sufficiently shown 
by the existence in all the larger land-masses of stratified 
rocks containing the remains of marine animals. Such 
marine fossiliferous sediments, which at one time formed the 
floor of the sea, are found to compose the great bulk of the 
existing dry lands, contributing very largely to even the 
loftiest mountain-ranges of the present day; and the fact that 
they consist of series of formations of different ages, and 
capable of being arranged in historical sequence, is sufficient 
proof that the submergence has been repeated more than 
once. 
While all geologists admit that during geological time 
there has been a repeated interchange of position between 
the dry lands and the shallow seas bordering these, scientific 
Opinion is not yet agreed as to the extent to which the 
deeper portions of the oceanic depressions have participated 
in this interchange. The older geologists, such as Lyell, 
held that elevation and depression were correlative pheno- 
mena, and that the admission that the dry lands had been 
repeatedly submerged beneath the sea, carried with it the 
admission that the present oceanic areas must have been 
repeatedly elevated to form dry land. In this connection 
it may be pointed out that the above theory by no means 
implies that an entire continent must necessarily be sub- 
merged at once, or that a whole ocean-floor should be at 
once elevated to form dry land. On the contrary, all that 
we know of earth-movements would lead us to believe that 
such changes of position, however extensive in their final 
results, must always have been accomplished bit by bit. 
In opposition to the old Lyellian theory, many scientific 
