The decade after the 1838 publication of
The British Museum was a barren one for Mackenzie in terms of new publications, but he did become involved in a series of business ventures. In 1844 his attempts to launch a British and Irish Sunflower Company, which would make a profit by selling sun flower seeds and promoting the use of sun flower oil in street lighting ventures and elsewhere, was greeted with derision in The Times and
The Morning Post. In 1846 Mackenzie married Susanna Hughes (1808-1881). The marriage had broken down by 1848 and in 1849 Mackenzie presented a petition to the House of Commons, asking for the short term reintroduction of the "whipping post" and "ducking stool" for "undutiful and runaway wives" whilst a parliamentary inquiry looked into "the baleful influence of...marriage settlements." The petition was not taken seriously, with an M.P. for South Devon, calling it "ridiculous", "absurd" and "most unbecoming." By early 1851 Mackenzie and his wife were living together again in Mayfair. In 1849 Mackenzie became secretary of
Charles Cochrane's National Philanthropic Association. Mackenzie's work included writing and compiling
A Plea for the Very Poor, on the plight of the "very poor" in the aftermath of the "hungry forties" in London, also including reports of the Highland Potato Famine and the Great Famine in Ireland. In 1850 Mackenzie led a campaign for the memorial to
Prince Aldolphus, Duke of Cambridge - recently deceased philanthropist and uncle of
Queen Victoria - to be a series of soup kitchens around London for the destitute. The National Philanthropic Association was running a single soup kitchen at Leicester Square in central London at this point. The plan was controversial, heavily criticised in the columns of
The Times newspaper, and didn't succeed. In 1851
Henry Mayhew described Colin Mackenzie as "enlightened and kindly" in
London Labour and the London Poor. In 1853, a year before his death, while Mackenzie was living at 69
Dean Street, Soho, he wrote a letter, giving his address as the "British Library", concerning his plan to develop "a Banking and Financial System which...will shortly become acceptable and convenient to every Trading individual in this and other Countries." ==Publications==