List of sources:
Chemical and Metallurgical Society of South Africa. Proceedings, 1894-1899, Vol. 1-2.
Chemical, Metallurgical and Mining Society of South Africa. Journal, 1904/5, Vol. 5, Members.
FamilySearch: Alexander Holmes Hartley. https://www.familysearch.org/ark:/61903/3:1:3Q9M-C91Q-Q9NW-J?view=index&personArk=/ark:/61903/1:1:QG6G-VNT8&action=view&cc=2721608 AND https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSQH-L99P-R?view=index&personArk=/ark:/61903/1:1:QPHX-VP2N&action=view&cc=2520237 AND https://www.familysearch.org/ark:/61903/1:1:KDCG-GD3
South African Association for the Advancement of Science. Report, 1905/6, 1910: Lists of members.