A history of the British forms is given in Gwyn Jeffreys's British Conchology (1862), and by Forbes and Hanley in British Mollusca.
His advocacy of temperance had much to do with securing the passing of the Forbes Mackenzie Act, which secured Sunday closing and shortened hours of sale for Scotland.
The most important subjects of his inquiries are enumerated by Forbes under the following five heads: - (1) The laws of polarization by reflection and refraction, and other quantitative laws of phenomena; (2) The discovery of the polarizing structure induced by heat and pressure; (3) The discovery of crystals with two axes of double refraction, and many of the laws of their phenomena, including the connexion of optical structure and crystalline forms; (4) The laws of metallic reflection; (5) Experiments on the absorption of light.
The method of Forbes (in which the conductivity is deduced from the steady distribution of temperature on the assumption that the rate of loss of heat at each point of the bar is the same as that observed in an auxiliary experiment in which a short bar of the same kind is set to cool under conditions which are supposed to be identical) is well known, but a consideration of its weak points is very instructive, and the results have been most remarkably misunderstood and misquoted.
Tyndall's own summary of the course of research on the subject was as follows: The idea of semi-fluid motion belongs entirely to Rendu; the proof of the quicker central flow belongs in part to Rendu, but almost wholly to Agassiz and Forbes; the proof of the retardation of the bed belongs to Forbes alone; while the discovery of the locus of the point of maximum motion belongs, I suppose, to me.
The lead in this direction was taken by British biologists, of pressure within and without the cyclone acted in the same beginning with Edward Forbes in 1839, and in 1868 a party on direction as the wind.
His first conspicuous success was achieved in 1862 with David Elginbrod, the forerunner of a number of popular novels, which include Alec Forbes of Howglen (1865), Annals of a Quiet Neighbourhood (1866), Robert Falconer (1868), Malcolm (1875), The Marquis of Lossie (1877), and Donal Grant (1883).
On his return he settled in Edinburgh; and, having attracted attention by his head of Forbes of Culloden and his full-length of the duke of Argyll, he removed to London, where he was patronized by the duke of Bridgewater.
Yet Duncan Forbes of Culloden, president of the Court of Session, after the outbreak of the war with Spain, reported amazing scarcity of money in the country, and strenuously advised legislative checks on the taste for tea, which naturally diminished the profits of the excise on more generous beverages.
Garrod was the more skilled and ingenious anatomist, Forbes had a greater acquaintance with the ornithology of museums and collectors.