Alfred Harry Wallis, civil engineer, entered the civil service of the Colony of the Cape of Good Hope in January 1897. From May 1901 he was district engineer at Bulawayo in the Rhodesian (now Zimbabwe) system of railways. In May 1904 he was transferred to De Aar, Northern Cape, as district engineer in the Cape Government Railways, but returned to Rhodesia as acting resident engineer and district engineer in September 1905. A few years later he published 'A section along the railway from Cape Town to the Victoria Falls' (The Geographical Journal, 1910, Vol. 36(3), pp. 339-343). In July 1910 he returned to South Africa as district superintendent in the South African Railways and Harbours (SAR&H). He was stationed in Mafikeng in 1917 and in Kimberley in 1924. In 1925 he was transferred to the post of divisional superintendent in the SAR&H at Windhoek, South West Africa (now Namibia), but by 1928 held a similar post in Pretoria. During World War I (1914-1918) he was appointed to temporary commissioned rank in the active citizen force. He attained the rank of Major in the Union Defence Force, but was placed on the retirement list in 1930.
Wallis sent a sample of calcareous tufa from Wondergat, some 30 km east of Mafikeng, North-West Province, to the South African Museum in Cape Town in 1908. However, his main scientific interest was in meteorology and climatology and led to a number of significant publications: 'An investigation of evaporation over free surfaces of water in inland South Africa' (Transactions of the Royal Society of South Africa, 1920, Vol. 8, pp. 283-292); The rainfall of South Africa (Johannesburg, 1920, 10 pp), reprinted from the South African Railways and Harbours Magazine of March 1920; The rainfall of Southern Rhodesia (Johannesburg, 1921, 3 pp), reprinted from the same magazine, September 1921; Sunspots and temperatures 1916. Shewing comparisons between Wolfer daily relative numbers and the mean daily maximum temperature at sixteen inland African stations (Kimberley, 1924, 16 pp); Rainfall, pressure, temperature and humidity: Mahalapye 1941, 1942 (Cape Town, 1942, 1943); Mean monthly rainfall of 14 stations [in Botswana] to December 1942 (Cape Town, 1943); and Meteorological observations: Mahalapye, from the records of Miss M. Giles, 1917-1943 (Cape Town, 1943, 11 pp).
Wallis was a Fellow of the Royal Meteorological Society. By 1917 he was a member of the Royal Society of South Africa and in 1924 was a member of the Astronomical Society of South Africa.