Joseph S. Curtis, son of the lawyer and author George T. Curtis, graduated at Harvard College, Massachusetts, and subsequently studied in Paris and at the Koenigliche Bergakademie (Royal School of Mines) in Freiberg, Sachsen, Germany, qualifying in geology and mining engineering. Back in the United States he joined the US Geological Survey, reporting on the mining geology of the Eureka district, Nevada (1882-1883), and on The quantitative determination of silver by means of the microscope (1884-1885). His most important work during these years was a monograph on The silver-lead deposits of Eureka, Navada, published by the US Geological Survey in 1884. He is said to have been in charge of the US Geological Survey during this early period in its history. In 1883 he married Marie Rose Behmer.
Curtis came to the Cape Colony in December 1886 and in March 1887 arrived in Johannesburg, having been sent there by the De Rothschilds family to work as geologist for H. Eckstein and Co (later Rand Mines Ltd). He was the first geologist employed by a mining company in South Africa and immediately began to study the geology of the gold-bearing reefs. Drawing a geological section of the Main Reef based on dip angles measured at various producing mines, he was soon able to predict where deep level mining would later commence, allowing the company to discreetly obtain control of the necessary properties. He advised that a diamond drill be obtained to prove the presence of the reef at depth, some 300 m south of an outcrop. The resulting borehole located the South Reef at a depth of 174 m and the Main Reef at 194 m, supporting his predictions with regard to both their continuity and depth. This result helped the Wernher-Beit-Eckstein group to take the lead in the development of gold mining on the Rand.
In 1892 Curtis became a foundation member of the South African Association of Engineers and Architects, serving on its council for 1892/3. He was also a foundation member of the Chemical and Metallurgical Society of South Africa (established in 1894; from 1902 the Chemical, Metallurgical and Mining Society of South Africa). From 1894 he served on the executive committee of the South African Chamber of Mines, and was a vice-president in 1895. He was also a foundation member of the Geological Society of South Africa in 1895, and served on its first council.
Curtis amassed great wealth in the Transvaal. He became a noted racehorse breeder and served on the council of the Witwatersrand Agricultural Society. In 1895 he joined the Reform Committee and was arrested in January 1896, following the Jameson Raid. Owing to his poor health he was allowed to recuperate at Muizenberg and was not charged for his part in the plot to overthrow the government of the South African Republic. He later returned to the Transvaal and became managing director of the holding company Transvaal Corporation Ltd. In 1899 he left South Africa and soon lost most of his fortune. After the Anglo-Boer War (1899-1902) he returned to the Transvaal, where he died a poor man.
Over a period of more than 20 years Curtis published several articles on the geology of the Witwatersrand and related topics. The first, "The banket deposits of the Witwatersrand" appeared in the Engineering and Mining Journal (New York) in 1890. In December 1894 he read a paper before the Chemical and Metallurgical Society of South Africa on "The reduction of Rand ores by amalgamation and concentration", published in the society's Proceedings (Vol. 1, pp. 76-80). In this paper he expressed the then fairly common view that solvent methods of gold extraction, by means of chlorine or cyanide, were unnecessary and that efficient recovery could be obtained by crushing and amalgamation only. History proved him wrong. Another paper, delivered before the South African Association of Engineers (Journal of Proceedings, 1903, Vol. 1, p. 225) dealt with "The Witwatersrand ore deposits and their relation to the various formations". Years later, in 1911, he published an article on "Borehole deflection and magnetism" in the South African Mining and Engineering Journal (No. 416, 419, 441). A paper by him on "Borehole deflections" also appeared in the Transactions of the South African Institution of Engineers (1913, Vol. 1, pp. 129-143). He is credited with inventing one of the earliest borehole survey instruments, when boreholes on the East Rand where deflected into a U-shape and returning towards the surface through strata already intersected (but see A.F. Crosse*, who also invented such an instrument in 1897). Finally, he wrote a brief sketch of the early history of the Village Main Reef Gold Mining Company Ltd, which was published in pamphlet form in Johannesburg in 1914.