INTRODUCTION
There are few more fascinating problems awaiting solution than that of the extent and relations of land and sea in the past history of the earth. Innumerable maps have been published, constructed on the evidence afforded by the occurrence and distribution of marine and continental deposits of which the age has been determined, as well as on less substantial grounds, such as the supposed existence of an ancient land barrier between sediments containing marine faunas believed to be contemporaneous, but differing strikingly in their character. On the other hand, a close similarity between terrestrial faunas and floras in areas now separated by the sea has been usually considered as sufficient evidence of a former land connection since submerged beneath the waves.
In none, however, of these attempted reconstructions of the geography of the past has it been assumed that the positions of the continents relatively to one another has been substantially changed, though such a possibility has been suggested by more than one student of cosmogony.
It has been reserved for Professor Wegener to collect a body of geological data that go far to demonstrate that such a relative movement has actually occurred.
Not only does the present and past distribution of life on the land furnish powerful arguments in support of his contentions, but the succession of the sedimentary rocks in areas now separated by thousands
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