He shortly afterwards obtained the appointment of surveyor to the local board of health of Kingston-upon-Hull, and devised a complete system of drainage for that town.
Clark devoted himself with zeal to his work, and very soon proposed a complete scheme for the drainage of the city, only imperfectly carried out owing to the expense.
He was selected by the colonial office in 1876, in concert with the government of New South Wales, to advise and report upon the water supply and drainage of Sydney.
During a residence of two years in the Australian colonies he prepared schemes of a like description for Port Adelaide, Newcastle, Bathurst, Goulburn, Orange, Maitland (the Walka Water Works), and Brisbane, and afterwards for Wellington and Christchurch in New Zealand.
Among Clark's inventions was his tied brick arch, of which examples exist in Calcutta and in other places in India; and he was joint patentee with William F. Batho of the well-known steam road roller.