FAMOUS GEOLOGISTS/Du Toit 191 Toit to visit Brazil, Uruguay, Argentina, and Chile, which were previously poorly mapped and not well understood He carried out a remarkable amount of field exploration in South America, meeting local geologists, including his old friend David Draper from South Africa, who was briefly managing the Boa Vista diamond mine in Minas Geraes Du Toit mastered the difficult literature, which was mainly in Portuguese, Spanish, and German His tour allowed him to study Devonian beds, fold ranges, and, as might be expected, the Karoo equivalents Back in South Africa, he was able to show Edgeworth David, en route to England, the key local sites relevant to the displacement hypothesis It was a fruitful meeting, and both geologists strengthened their support for the notion of continental drift The Carnegie Institution published du Toit’s Geological Comparison of South Africa with South America in 1927 The book contained, inter alia, a chart showing the stratigraphic column from the Devonian to the Jurassic for selected South American countries The boundaries of the Afro-American landmass were shown to have a bearing on the displacement hypothesis, which was becoming more widely known through the English translation of Wegener’s Origin of Continents and Oceans (1924) By this time, du Toit had made contact with the Dutch geologist Willem van Waterschoot van der Gracht, who was then working in the petroleum industry in the USA Van der Gracht had become an apostle of continental drift and persuaded the American Association of Petroleum Geologists to organise a conference in New York in late 1926 to discuss the theory Despite the contributions of several supportive American speakers, including Reginald Daly, a prejudiced group, led by Charles Schuchert, condemned the theory out of hand Unable to attend, du Toit was dismayed by the intolerant attitudes of some people and their personal attacks on Wegener and others He sent a paper to support Van der Gracht’s publication of the proceedings, which appeared in 1928, and in the following years added further publications in journals such as the American Journal of Science; even as late as 1944 he made a rejoinder to G G Simpson regarding his ideas on Tertiary mammals and continental drift For some years, du Toit had been planning to write a textbook on the geology of South Africa The first edition, published in 1926, was the first synthesis of its kind A second revised edition followed in 1939 Du Toit died before he could complete his revision of the third edition, but his old friend and colleague Sidney Haughton carried on the task and the book was published in 1954 Years of Work and Wandering In 1927, du Toit was invited to join De Beers Consolidated Mines as a consulting geologist, specializing in diamondiferous kimberlite pipes and alluvial gravels Once again, he could travel extensively in Africa, but now in an official capacity These travels, to areas in which De Beers had an interest, afforded him many opportunities to study the local geology He could also visit other countries: the USA and Canada in 1932; the USSR in 1937; and India in 1938 Little concerning the areas visited survives in published form However, from a cache of photographs and other documents discovered recently, we know that he travelled widely in the western USSR, from the Urals down to the Ukraine and the coastal area of the Black Sea Du Toit’s greatest contribution to geology, and also his swansong, was his book Our Wandering Continents (1937), in which he assembled the observations, deductions, comparisons, and syntheses of facts and theories of a lifetime A brief description of the features of the book is in order After a review in which he acknowledged the work of his predecessors, he referred to tectonism, volcanism, palaeoclimates, plant fossils, and geosynclines to explain and describe his grouping of the ancient continents and his theory of drifting The distribution of glacials formed, as before, the core of his arguments We should note that du Toit now used the term ‘Gondwana’ for the southern supercontinent For the northern supercontinent he introduced the term ‘Laurasia’, derived from Laurentia (the eastern North American shield) and Asia Additionally, the book contained a discussion of Arthur Holmes’s suggestion of fracturing of continental blocks by subcrustal convection movements to explain spreading Du Toit also included a figure showing the development of continental rifting that owed something to Holmes’s famous figure of 1929, representing convection and continental fracture But du Toit doubted whether subcrustal convection was ‘wholly competent to account for continental drift’ The evidence for the former linkage of the southern continents was illustrated in several convincing diagrams (Figures 3, 4, and 5), and the structural correspondences between western Europe and North America were also depicted, along with a suggested pattern for the opening of the North Atlantic (see Figures and 7) Throughout the book, du Toit challenged the geological community to accept his theories, but he did not live long enough to witness the acceptance of continental drift nearly two decades later