The main interest of the collection lies in the material it contains relating to the history of science. The fields to which James David Forbes made contributions were electricity, meteorology, physics of heat, and the theory of glaciers. This last subject involved Forbes in heated personal controversy, and there is much material relating to this. More generally, there is a good deal of information relating to the British Association for the Advancement of Science (generally referred to subsequently as the British Association), especially its formative years; the Royal Society of Edinburgh (he was made a member as soon as he reached the age of 21, and served as General Secretary 1840-51) and the Royal Society, London, of which he became a member in 1832. His work on the effects of heat involved him peripherally with some of the civil engineering achievements of his period.
David Brewster (1781-1868), William Whewell (1794-1866), George Biddell Airy (1801-1892) and Roderick Murchison (1792-1871) are those with whom Forbes had the fullest correspondence, but few of those working in the physical sciences in Britain and on the continent between 1830 and 1860 are not represented in the collection. Long and intimate contacts are few, though Forbes had great respect for those who supported him early in his career, such as Brewster, Airy and Whewell, and later in life was supportive to younger enthusiasts for the Alps, particularly Alfred Wills and Anthony Adams Reilly. He also developed close friendships with some of his former students, and in particular Edmund Chisholm Batten. Although the relationship cooled for many years (Alicia Forbes clearly disliked Batten), the closeness returned during Forbes' last illness.
Forbes's continental travels to study hot springs, glaciers, traces of volcanic action and the many other things which interested him are well documented in his journals, but he published much of this during his lifetime. Also well covered is his conduct of the Natural Philosophy class at Edinburgh University between 1832 and 1860. His lecture notes were said to have been almost entirely destroyed after his death, according to his wishes. There are among his papers, however, not previously catalogued, what appear to be lecture notes, perhaps not the final versions, but enough to give some idea of what and how he was teaching.
As well as scientific correspondence, the letters contain much business material. Some of this is personal, relating to banking, investments and renting and maintaining property. There are also letters relating to his employment at Edinburgh University, which was run by the Town Council, with whom J.D.F. had a number of arguments over pay, equipment and their general attitude to the relative importance of sciences and arts subjects.
The material relating to Forbes' time as principal of the United College, St Andrews, (1859-68), is especially important, both generally in giving information on dealing with the Commissioners following the 1858 Universities (Scotland) Act, and particularly with regard to the developments associated with Forbes' name - the reorganisation of United College finances, the founding and organisation of the College Hall Company and the restoration of St Salvator's Chapel. His interest in the wider problems of and developments in education can be traced throughout the correspondence.