In 1851 he published in the collection of the ‘Cavendish Society’ a ‘Life of Henry Cavendish [q. v.]’, his most notable performance in scientific history, which became his favourite pursuit. Wilson fully established the priority of Cavendish with regard to the experimental results on which the theory of the composition of water is based; he showed that the advocates of James Watt's claims, including James Patrick Muirhead and Francis, lord Jeffrey [q. v.], had overestimated Watt's merits; but, in spite of much knowledge and labour, he did not fully master the mass of material he had accumulated relating to the ‘water controversy.’ Their common interest in this matter had already in 1846 (Life of Cavendish, p. viii) led to a warm friendship between Wilson and Jeffrey. In 1852 Wilson published a vigorous letter addressed to Spencer Horatio Walpole [q. v.], the home secretary, on ‘The Grievance of University Tests,’ with reference to the chair of chemistry vacant at Glasgow by the death of Thomas Thomson (1773–1852) [q. v.] He published in the same year the ‘Life of Dr. John Reid [q. v.]’ (a personal friend), which reached a second edition immediately. In November 1853 Wilson published in the ‘Edinburgh Monthly Journal of Medical Science’ the first of a long series of papers on ‘Colour-Blindness,’ continued in the ‘Transactions of the Royal Scottish Society of Arts,’ and republished with additions, under the title ‘Researches on Colour-Blindness,’ in 1855. Wilson examined personally 1,154 cases of colour-blindness, and was the first in England to point out the extreme importance of testing railway-servants and sailors for this defect. The researches of the Abbé Moigno (1804–1884), who claimed to have preceded Wilson in this, were unknown to him. The Great Northern Railway at once adopted Wilson's recommendations, and other bodies followed suit. James Clerk Maxwell [q. v.], then working at his colour-top, contributed an appendix to Wilson's book, of which he thought highly.
In February 1855 Wilson was appointed director of the Scottish Industrial Museum about to be founded, and, later in the same year, regius professor of technology in the Edinburgh University. His inaugural lecture, ‘What is Technology?’ was published in extenso. In the autumn of 1856 he prepared for the press at Melrose his ‘Five Gateways of Knowledge,’ a popular and ornate account of the five senses. His opening lecture for the session of 1856–7, ‘On the Physical Sciences which form the Basis of Technology,’ written about the same time, is far more mature than Wilson's other popular lectures, and shows a real grip of the correlation of the various sciences, while his natural exuberance of imagination and diction is chastened. In 1858 William Gregory (1803–1858) [q. v.], then professor of chemistry in the university, died, and Wilson became a candidate for the vacant chair; but, although assured that he would be elected unanimously, he withdrew his candidature on account of his ill-health (Memoir, p. 456). His salary as director of the museum was at the same time increased from 300l. to 400l. a year.
He had weakened steadily from year to year; in November 1859 a cold brought on by exposure proved fatal, and he died on 22 Nov. A public funeral was decided on, and he was buried in the Old Calton burial-ground on 28 Nov. 1859. He was unmarried; his mother, his brother Daniel, his sister Jessie Aitken Wilson (later Mrs. James Sime), his biographer, and another sister, survived him.
Wilson's experimental work, although ingenious and solid, contains little of marked originality; it is by his ‘Life of Cavendish’ and his work on ‘Colour-Blindness’ that he will be chiefly remembered. From the literary point of view his writings, both prose and verse, show a fertile imagination, but little judgment or reserve, although here and there the expression is striking. Religion played an essential part in Wilson's life, and without a trace of either pedantry or unction he was genuinely anxious to exert religious influence over others. He protested strongly against the existence of evil being regarded as other than an unsolved problem; but his religious views do not otherwise differ markedly from those of orthodoxy. By his popular lectures and writings, and still more by his force and charm of character, he exerted considerable influence on his Edinburgh contemporaries.
A steel engraving of Wilson by Lumb Stocks, A.R.A., precedes the ‘Memoir’ by his sister; and there is another engraved portrait prefixed to the ‘Counsels of an Invalid.’
Besides the works mentioned Wilson was the author of:
- ‘Chemistry,’ 1st edit. 1850; 2nd edit. revised by Stevenson Macadam, 1866; 3rd edit. revised by H. G. Madan, 1871.
- ‘Electricity and the Electric Telegraph,’ 1st edit. 1856; 2nd edit. 1859.
- ‘The Five Gateways of Knowledge,’ 1st edit. 1856; 8th edit. 1880.
- ‘Memoir of Edward Forbes’ (completed by Sir Archibald Geikie, F.R.S.), 1862.
- ‘Religio Chemici,’ essays, chiefly scientific, collected posthumously and edited
