John Cameron became a member of the Rhodesia Scientific Association in 1905. Before that, in December 1903, he read a paper on "Characteristics of Rhodesian soils" before is members. The paper was published in the association's Proceedings (Vol. 4, pp. 52-66).
He may be the same person as John Cameron who published two articles, "The fruits of Mysore" [in India] (1889) and "Hybrid coffee in Mysore" (1898), in Kew Bulletin.