Harry P. Saunders joined the civil service of the Cape Colony in July 1890. On 1 July 1893 he was appointed to a newly created post, inspector of water drills, in the Department of Agriculture. He submitted annual reports to Parliament for 1893 to 1897, the last of which included a geological sketch plan and section of Robben Island. In 1895 he was one of several experts interviewed by the Select Committee on Geological Survey. Following this committee's report the Geological Commission of the Cape of Good Hope was established in November that year. In 1898 the position of inspector of water drills became part of the Department of Public Works, with which he was still associated, probably as a consultant, in 1908.
Saunders compiled some important publications relating to the geology of South Africa. Underground water supply of the Colony of the Cape of Good Hope, with special reference to the working of the diamond drill (Cape Town, 1897, 62p) was a practical handbook for working government drills, but also dealt with the geological aspects of prospecting for water. It included five diagrams from Professor A.H. Green's* Report on the coals of the Cape Colony; also an appendix containing the output of boreholes all over the colony, and drawings of hand and steam-powered diamond drills. Articles with a similar content were published in the Agricultural Journal of the Cape Colony (Vol. 11, pp. 183-190, 242-249, 314-330) that same year. Several years later Saunders wrote the Report of the Select Committee on the system of deep well boring and the use of diamond drills (Report C1, 1903, 43p).
Another significant publication by Saunders was his Bibliography of South African geology, published in Cape Town by the Geological Commission of the Cape of Good Hope in 1897. It listed nearly 600 items and was the first of its kind. Later bibliographies of South African geology were compiled by M. Wilman* (1905) and A.L. Hall* (1922).
Saunders became a member of the South African Philosophical Society and of the Geological Society of South Africa in 1895, but his membership of both lapsed after a few years. In 1897 he presented specimens of copper pyrites and bornite from Namaqualand to the South African museum, followed by a sample of Dwyka conglomerate from Mafikeng in 1898.