retirement from the army on 23 Feb. 1875, with, the honorary rank of lieutenant-general, a member of the council of India.
In 1877 Strachey was sent to India to arrange with the Indian government the terms for the purchase of the East Indian railway, the first of the guaranteed railways to be taken over by the government on the termination of the original thirty years' lease, and he initiated the policy of and drew up the contract for the continued working of the railway by the company under government control. While in India he presided with great ability over a commission to inquire into the causes of the terrible famine and to suggest possible remedies. He also filled the post of financial member of council during the absence of his brother John, and was thus associated with the Indian government in the negotiations which led to the rupture with Shere Ali and war with Afghanistan. On his return home in 1879 Strachey was re-appointed to a seat in the council of India ; he was one of the British commissioners at the Prime Meridian Conference held at Washington, U.S.A., in 1884, and was elected one of the secretaries ; in 1887 he was chosen president of the Royal Geographical Society and held the post for two years ; he was also an honorary member of the geographical societies of Berlin and of Italy. He resigned his seat on the India council in 1889 to become chairman of the East India Railway Company, and his beneficial rule is commemorated by the 'Strachey' bridge over the river Jumna, opened shortly before his death. He was also chairman of the Assam Bengal Railway Company, and only resigned these positions when nearly ninety years of age, in consequence of increasing deafness. Under his management the East India railway became the most prosperous trunk line in the world.
In 1892 Strachey was one of the delegates to represent India at the international monetary conference at Brussels, and the same year he was a member of the committee on silver currency presided over by Lord Herschell, when there was adopted a far-reaching reform which he had proposed when finance minister in India in 1878, viz. to close the Indian mint to the free coinage of silver. In June 1892 he received from the University of Cambridge the honorary degree of LL.D.
Strachey did much good work for the Royal Society, served on its council four times, from 1872 to 1874, 1880 to 1881, 1884 to 1886, and 1890 to 1891, and was twice a vice-president ; he was a member of its meteorological committee (which controlled the meteorological office) in 1867, and he was a member of the council which replaced the committee in 1876, and from 1883 to 1895 was its chairman. From 1873 he was on the committee of the Royal Society for managing the Kew observatory. The royal medal of the society was bestowed upon him in 1897 for his researches in physical and botanical geography and in meteorology, and the Royal Meteorological Society awarded him the Symons medal in 1906. His most important scientific contributions to knowledge were made in meteorology. He laid the foundations of the scientific study of Indian meteorology, organising a department whose labours have been of use in assisting to forecast droughts and consequent scarcity and of no little advantage to meteorologists generally. For years he served on the committee of solar physics. A sound mathematician, Strachey delighted in mechanical inventions and especially in designing instruments to give graphic expression to formulas he had devised for working out meteorological problems. In 1884 he designed an instrument called the 'sine curve developer' to show in a graphic form the results obtained by applying to hourly readings of barograms and thermograms his formula for the calculation of harmonic coefficients. In 1888 and 1890 he designed two 'slide rules,' one to facilitate the computation of the amplitude and time of maximum of harmonic constants from values obtained by applying his formula to hourly readings of barograms and thermograms ; the other to obtain the height of clouds from measurements of two photographs taken simultaneously with cameras placed at the ends of a base line half a mile in length. A further invention was a portable and very simple instniment, called a 'nephoscope,' for observing the direction of motion of high cirrus clouds, whose movement is generally too slow to allow of its direction being determined by the unaided eye.
Strachey had been granted a distinguished service pension and created C.S.I, in 1866, after thirty years' service. Subsequently he declined the offer of K.C.S.I. But on the diamond jubilee of Queen Victoria in 1897 he was gazetted G.C.S.I. After leaving India he lived at Stowey House on Clapham Common ; later he moved to Lancaster Gate, and only a few months before his death to Hampstead. He died at 67 Belsize Park Gardens
