Tenda to the Semmering. 'The Alpine Guide' (1863–8) was undoubtedly the most important literary product of a life of very various activities. Its plan was at once comprehensive and clear. A preface dealing with the Alps and Alpine travel generally, both from the scientific and practical point of view, was prefixed to the work. The range was then divided into three sections — the Avestern, central, and eastern Alps — each described in a single volume. The lesser subdivisions into groups, based mainly but not absolutely on physical considerations, were made with great skill and have proved practically convenient. Throughout the work the special geological and botanical features of each district are insisted on, while the travelling student finds observations in detail thrown in at every fitting opportunity. The object of the writer is not to conduct his readers along certain beaten tracks, but to put them in a position to choose for themselves such routes as may best suit their individual tastes and powers, to give advice as to what is best worth notice, and to show what is open to the prudently adventurous. The main purposes of the book are kept constantly in sight, and it is written throughout in a vigorous style which keeps its freshness to the end and makes the descriptive passages pleasant reading, while they are relieved from time to time by shrewd observations, flashes of quiet humour, or tersely told personal adventures.
Ball was himself rather a scientific traveller than a great climber, and his taste for solitary rambles was perhaps too strong to make the numbers needed for safety in the region above the snow level altogether congenial to him. But the extent of his Alpine travels, mostly on foot, is indicated by his own statement. Before 1863 he 'had crossed the main chain forty-eight times by thirty-two different passes, besides traversing nearly one hundred of the lateral passes.' His first Alpine feat was the passage of the Monte Rosa chain by the Schwarz Thor in 1845, and among the summits of which he made the first or early ascents were the Pelmo, the Tergloo, and the Cima Tosa.
In 1871 Ball accompanied Sir J. D. Hooker and Mr. G. Maw in an expedition to Morocco. The object of the journey was to investigate the flora of the Great Atlas and determine its relations to those of the mountains of Europe. In 1882 Ball made a five months' voyage to South America.
Ball's contributions to science were mainly geographical, physical, and botanical. In the first the most important are 'The Alpine Guide' (3 parts, London, 1863-8, 8vo; translated into Italian 1888; the first volume has been re-edited as a permanent memorial to him by the Rev. W. A. B. Coolidge for the Alpine Club, 1898), his 'Journal of a Tour in Morocco,' 1878, and his 'Notes of a Naturalist in South America,' 1887, of which Sir J. D. Hooker writes: 'High authorities have pronounced them to be deserving of a corner of the same shelf with the works of Humboldt, Darwin, Bates, and Wallace.' Of Ball's papers on physical subjects the most important were concerned with meteorology or hypsometry. His contributions to botany were both critical and theoretical. Among the first his 'Spicilegium Floræ Maroccanæ' (Linnean Soc. Journal, 'Botany,' 1878, xvi. 287-742) will always remain a classic both for its merits and as the earliest work on the flora of that region. His 'Distribution of Plants on the South Side of the Alps,' which he left unfinished, was published after his death in the 'Transactions of the Linnean Society' in 1896. Sir J. D. Hooker thus describes Ball's theoretical essays in botany: in that '"On the Origin of the Flora of the European Alps" (Geogr. Soc. Proc. 1879, pp. 564–88), he argued for the high antiquity of the Alpine flora, and for the earliest types of flowering plants having been confined to high mountains (thus accounting for their absence in a fossil state), due to the proportion of carbonic acid gas in the lower regions of the earth being too great to support a phenogamic vegetation. He further held that existing modes of transport are insufficient to account for the present distribution of plants. His other theory relates to the South American flora, and is given in his "Naturalist's Journal." In this he assumes that the majority of the peculiar types of the whole South American flora, except possibly a few that originated in the Andean chain, had their primitive homes on that hypothetical ancient mountain range which he had placed in Brazil, and to great heights on which they would, under his theory, be restricted through the operation of the same cause that restricted the European early types to the highest Alps.'
Ball suffered from ill-health during the last years of his life. He died at his house, 10 Southwell Gardens, South Kensington, on 21 Oct. 1889,
Ball married twice, in 1856 and 1869. His first wife, by whom he had two sons, who survive him, has been already named; his second was Julia, daughter of F. O'Beirne, esq., of Jamestown, co. Leitrim. He was elected a fellow of the Royal Society on 4 June 1868, and an honorary fellow of his
