Page:History of the Royal Astronomical Society (1923).djvu/175

 1860-70] ROYAL ASTRONOMICAL SOCIETY 149 And so it came about that Hansen's Tables held sway for a genera- tion. Of Airy's own later work this is not the place to speak. Meanwhile new activities had grown up in Airy, and he strove through the Society to promote co-operation among astronomers on another problem of prime importance, the solar parallax. The inadequacy of Encke's value, 8^.57, which was adopted in 1824 and was still generally in use, had been indicated by Hansen's, Le Verrier's, and Foucault's researches ; and Airy said that new observations could alone help us satisfactorily to correct our obviously inadequate knowledge of the sun's distance. As early as 1857 he passed in review the methods " available for correcting the sun's distance in the next twenty-five years " ; and while laying special stress on the transits of Venus in 1874 and 1882, he pointed out the desirability of taking advantage of the favourable opposi- tions of Mars in 1860, 1862, and 1877. But activities of this kind were the essence of Airy's life, and this is not the place to follow them up in detail. It is enough to say that the influence of his personal and official labours contri- buted enormously to the regard in which the Society was held both at home and abroad. Simon Newcomb [1835-1909], who in his Reminiscences of an Astronomer, published in 1903, has recorded his experiences in visits to England and elsewhere in Europe his first visit to Greenwich was in 1870 gives what one may regard as a contem- poraneous view of Airy. " We may look back on Airy as the most commanding figure in the astronomy of our time. He owes this position not only to his early work in mathematical astronomy, but also to his ability as an organiser. . . . He introduced production on a large scale into astronomy." The problem of determining the movement of the Solar System in space was brought into prominence again in this decade by the increase in our knowledge of the proper motions of the stars. Airy introduced his new method of dealing with such proper motions, in a paper published in the Memoirs, 28, 143, dealing with 113 stars. Sir William Herschel's method, based upon an incorrect assumption that the brighter stars are in general nearer to us than faint stars, was unsuitable for the discussion of proper motions of a great number of stars, though it was well adapted to the limited facts of observation known to him. Airy sought for a method which should not, like Bessel's and Argelander's methods, depend upon a knowledge of an approximate position of the apex of the solar motion. He accordingly decided that instead of using the apparent angular motions of the sun and stars as exhibited on the surface of a globe, it would be preferable