He entered politics in 1869, having first been a farmer and surveyor. At this time the Cape Colony was in the transition stage of representative government. He represented, firstly, the district of Namaqualand, then Wodehouse and finally Victoria West. After the granting of responsible government to the Cape Colony in 1872, he served in the cabinet of its first Prime Minister, Sir John Molteno, from 1875 to 1878, then in the Scanlen ministry from 1881 to 1884. He was Treasurer-General under Cecil Rhodes from 1890 to 1893. He ended his relationship with Cecil Rhodes after the Jameson Raid in December 1895.
Thereafter he become an opponent of the mining interests and British imperialism in Southern Africa. This gained him the sympathy and cooperation of the Afrikaner Bond led by Jan Hendrik Hofmeyr. He was a member of the Cape Commission charged with investigating the Jameson Raid and was responsible for writing its report. He again served as Treasurer General of the Cape in the ministry of W.P. Schreiner from 1898 to 1900. He tried but failed to prevent the Second Boer War.
In 1908 his South African Party together with the Afrikaner Bond won control of the Assembly and he served as Prime Minister of the Cape Colony from 1908 until the formation of the Union of South Africa on 31 May1910.
He was a leading figure in the National Convention which brought about this Union. It was thought that he might become the first Prime Minister of the new union. Lord Gladstone, the first Governor-General, however, asked the Afrikaner statesman, Louis Botha to form a government. Merriman declined to accept a post in the first Union Cabinet.
He continued to serve in the Parliament of South Africa, representing first the constituency of Victoria West, and then Stellenbosch. He carried on a lively correspondence with Jan Christiaan Smuts, constantly warning him about possibilities of rebellion and civil war with Afrikaner sections of the white population who objected to South African cooperation with Great Britain against Germany in World War I, especially the South African invasion of German South West Africa, now Namibia. He was one of only a few members of Parliament who the opposed the Native Land Act, legislation introduced in 1913 which drastically limited African ownership of land.
Personal Life
In 1874 he married Agnes Vintcent daughter of Mr. L. Vintcent, a member of the Cape Legislative Council. In 1892 he purchased a farm which later became Rustenberg Wines. The company has honoured him with a variety of wine named after him.
He died, aged 85, in Stellenbosch, South Africa, in 1926.
