John Noble Jack (usually referred to as J. Noble Jack), agriculturalist, was appointed principal of the College of Agriculture at Elsenburg, near Stellenbosch, from 27 January 1905. That year he conducted some experiments dealing with the fertilisation of oat hay on vlei and hillside land. The results were reported in "The manuring of oathay at Elsenburg College", published in the Agricultural Journal of the Cape of Good Hope (1906, Vol. 28, pp. 574-580). Jack resigned his post in June 1907 and was appointed as director of agriculture of the Cape of Good Hope. In this capacity he published an article on "Arable farming" in the Agricultural Journal of the Cape of Good Hope (1908, Vol. 33(3), pp. 291-296) which dealt mainly with the economics of cerial production.
By 1910 Jack was living in Caledon and had become a member of the South African Association for the Advancement of Science.