Hendrik A. Brouwer, Dutch geologist, was the son of Egbertus L. Brouwer and his wife Hendrika Poutsma. He attended school in Haarlem and then studied mining engineering under Gustaaf A.F. Molengraaff* at the Technische Hoogeschool (Technical University) in Delft, where he received his diploma in 1908. His doctoral research involved a study of Molengraaff's collection of South African nepheline syenites, guided in part by Alfred Lacroix at the Sorbonne and the Museum of Natural History in Paris. In 1910, in the company of E.C.N. van Hoepen* and A. van der Ham, he undertook a study tour to South Africa to collect material for his doctoral research. Among other places Brouwer visited the Pilanesberg in Transvaal. He received his doctoral degree in the technical sciences at Delft in October 1910 on the basis of a thesis, Oorsprong en samestelling der Transvaalse nepheliensyenieten (Origin and composition of the Transvaal nepheline-syenites). In this work, which was published in Den Haag, he provided the first proper description of certain extraordinary rocks in the vicinity of Pretoria and Pilanesberg. His research was mainly a laboratory project and was not backed up by essential field observations. However, he based several papers on it, which were published in European journals during 1909 to 1911. He has been criticised for creating unnecessary rock names, such as pienaarite, a variety of foyaite from the Transvaal (1910). However, he also successfuly named the mineral molengraaffite (1911), which he identified in Transvaal rocks, in honour of his mentor and promoter.
Towards the end of 1910 Brouwer went to the Dutch East Indies and worked as a mining engineer and geologist in Timor, Sumatra and the Moluccas for six years. During this time he developed his main interests, namely the younger folded belts, and the relation between vulcanism and structural geology. In 1918 he became professor of historical geology and palaeontology at Delft Technical University, and from 1925 also taught tectonics at the State University at Utrecht. In 1928 he became professor of general and practical geology and petrology at the University of Amsterdam, where he remained to his retirement in 1957. Here he developed a first rate geological institute and played a leading role in various scientific societies and activities. He undertook study tours to Brazil (1919), North America (1921-2, 1933, 1935), Sulawesi (Indonesia, 1929), and the Lesser Sunda Islands (Indonesia, 1937). His visit to Brazil led to a paper (in Dutch) on the alkali rocks of the Serra de Gericino, north-west of Rio de Janeiro, and the similarities between the eruptive rocks of Brazil and South Africa (1921). A few years later he wrote a paper 'On the geology of the alkaline rocks in the Transvaal' (Journal of Geology, 1925).
During his first visit to North America Brouwer delivered a series of lectures on the geology of the Dutch East Indies at the University of Michigan. These lectures were published in New York in 1925. His geological investigations in the East Indian Archipelago were published in five volumes in 1922-1927. The results of his investigations on the Lesser Sunda Islands were reported in Geological expedition of the University of Amsterdam to the Lesser Sunda Islands..., 1937 (Amsterdam, 4 vols, 1940-1942). An English translation of his book on the geology of Celebes, which he visited in 1929, was published with the title Geological explorations in the island of Celebes (Amsterdam, 1947, 346p). His last major work dealt with Vulkanen (Volcanoes; Den Haag, 1946, 154p). He was promotor for some 50 doctoral candidates and is recognized as one of a small number of influential Dutch research leaders in the earth sciences. He was a member of the Royal Netherlands Academy of Sciences and was active in several European geological societies. From 1923 to 1948 he was associate editor of the Journal of Geology (Chicago).
In 1922 Brouwer published Volume 1 of his Practical hints to scientific travellers in Leiden. It includes "Notes of travel in South and East Africa", by Percy A. Wagner* and Tudor G. Trevor*. He was an inspiring teacher and had great personal charm, but could also be militant and aggressive and was involved in many conflicts. He had a strong interest in mysticism and was a firm believer in astrology. In 1909 he married Louise Betsy van der Spil, with whom he had three children. They were divorced in 1930. His second marriage, to Olga M. Labouchere, also ended in divorce.