Cass's father died in 1825, leaving his widow, who ran a girls' day school, with six children to raise.

[1] In return for his sponsored education, Cass was committed to a seven-year apprenticeship at sea as a trainee mariner, allocated to John Skelton, Commander of the ship Africa.

He was back in Northland for the Battle of Kororareka on 11 March 1845, and participated in action against Te Rauparaha in the following year.

When Thomas was sacked in January 1851 by the agent of the Canterbury Association, John Robert Godley, he became chief surveyor and held that role until his retirement in early 1867.

Charles Fooks (a brother-in-law of Guise and Joseph Brittan) and Edward Dobson were defeated (at 51 and 21 votes, respectively).

After William Hamilton[10] resigned from the Executive Council in mid-June 1857, Canterbury's Superintendent James FitzGerald made two appointments on 29 June of that year: Cass and Richard Harman.

[6][11][12] After FitzGerald resigned in September 1857, William Sefton Moorhouse succeeded him as Superintendent in the following month, and Cass remained on the Executive Council.

[13] The elections for the second Provincial Council were held in November 1857, where six candidates stood for four positions in the Town of Christchurch electorate.

[19] Immediately after his departure, the Provincial Council discussed an honorarium for Cass, who had signalled his intention to retire as chief surveyor due to his chronic asthma.

[20][21] Cass went to England in 1867 and became an immigration agent for the Canterbury Province, succeeding Crosbie Ward, who had died in London in November 1867.

[25] He was visited by Dr Thomas Hocken in 1894 for an interview, and at the time, Cass was bedridden, deaf, and repeated himself much.

[27] The Cass railway station, which for many years was the railhead whilst the Midland Line was under construction and during which the township had a population of 800, was painted in 1936 by Rita Angus; it is "one of New Zealand's best-loved works of art".