Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/102

76 of many differences of opinion. The connection between Australia and India (united with Madagascar and South Africa) disappeared soon after the beginning of the Jurassic period; the connection between South America and Africa disappeared in the Lower to Middle Cretaceous; and the connection between India and Madagascar disappeared at the transition from Cretaceous to Tertiary. At all three places a land connection had prevailed from the Cambrian period until these points of time. The connection between North America and Europe was vastly more irregular. But nevertheless here also, in spite of the frequent differences, there exists a far-reaching agreement of views. The connection was repeatedly disturbed in the more ancient periods, namely, in the Cambrian and in the Permian, as well as the Jurassic and Cretaceous, but obviously only by transgressions, which later permitted the restoration of the continuity. The final breaking off of relations, which corresponds to the present-day separation by a broad ocean, can only first have happened in the Quaternary.

Of entirely different value are the two separations that we shall next discuss, which are concerned with the connections of the Antarctic with Patagonia on one side, and with Australia on the other. The strong majority of negative votes in this case evidently originates from the slightness of our knowledge concerning Antarctica, which has induced many authors to disregard a connection of this continent with the others, since no reason existed for such an hypothesis. Because of this, only the positive proportion of the votes will be considered. These seem to show that in the Drake Straits an exchange of forms took place chiefly from the Cretaceous up to the Pliocene, as well as at various times previously, and between Australia and the east of Antarctica particularly from the