Du Toit, Alexander Logie (1878-1948), was a South African geologist. His book The Geology of South Africa (1926) became a standard reference work on the subject. He also made a major contribution to the theory of continental drift. According to this theory, Earth's crust is divided into a number of large plates that move slowly over the surface of the globe. The continents are embedded in these plates and slowly drift with them. Du Toit's book The Wandering Continent (1937) showed that there were important links between the Karoo area in the southern part of South Africa, and similar places in South America, India, and Australia.