List of sources:
Draper, J.R. The engineer's contribution: a history of the South African Institution of Mechanical Engineers, 1892-1967 (p. 245). Johannesburg: SAIME, 1967.
Journal of the Transvaal Institute of Mechanical Engineers, 1906-1910, Vol. 5-8.
Orr, J. Presidential address. Associated Scientific and Technical Societies of South Africa, Annual Proceedings, 1938, pp. 15-86 (see p. 21).