A century ago geologists first began to consider the possibility of large lateral shifts of the continents. Reconstructions of the ancient positions of the continents have been proposed at various times since to try to explain past climatic zones, faunal distributions, similar orogenic sequences and structural trends on adjacent continents, and many other detailed geological events. Prominent amongst the hypotheses is that generally known as the Continental Drift Hypothesis, developed independently by F. B. Taylor and A. Wegener fifty years ago and later modified by A. L. du Toit andothers. In this hypothesis two primeval continents, Laurasia and Gondwanaland, are supposed to have formed at the north and south poles, to have broken up and possibly to have grown, and the pieces to have drifted to the positions of the present continents. The continents are moved around by forces of unknown origin and their interaction with each other and with the substratum gives rise to orogenesis. Due in large part to the lack of any known forces capable of producing these movements the hypothesis is nowadays less favoured than others requiring no drift. Recently, however, the study of palaeomagnetism has provided an independent line of evidence. From it the ancient latitudes and orientations of the continents can be worked out and relative displacements may possibly be revealed.