Page:History of the Royal Astronomical Society (1923).djvu/221

 1870-80] ROYAL ASTRONOMICAL SOCIETY 193 which go back in date to the year 1819, and to the publication (in May) of an account of how the Schwabe drawings were acquired by the Society. In the year 1864, Messrs. De la Rue and Balfour Stewart wrote to Schwabe to request that he would allow his original manuscripts to be sent to England. Schwabe was loth to part with them, but consented to do so on the condition that they should be sent back to him *' at any time that I should be desirous of looking into them during the short time of life still left to me. I do not think that I shall have an occasion to avail myself of the permission asked for ; but permit me kindly to believe that it is in my power to do so. After my death you may consider the whole of the observations as the property of the Royal Astronomical Society." Thirty-nine volumes of Schwabe's diaries (1825-67) were therefore sent to the Kew Observatory, and were transferred to the library at Burlington House in 1880. Mention of the subject of sun-spots recalls the fact that the Rev. Temple Chevallier pre- sented to the Society in 1851 his valuable series of observations of spots made at Durham Observatory, bound in two volumes, which are now in the library. The writer of the obituary notice of Canon Chevallier remarked that he was the first to institute in England the regular continuous observation of the solar spots, and that his methods were afterwards adopted by Mr. Carrington, who had been an Assistant at Durham under him. These state- ments were contradicted by Carrington in a note in the Monthly Notices (34, 250), in which he pointed out that Harriot (1610-13) was the first English sun-spot observer, and that his (Carrington's) methods were quite independent of any that had been hitherto used. The planet Mars was an object of interest for more than one reason in the year 1877. It was in opposition on September 6, and nearest the earth on September 9, the distance being 0-377 in astronomical units, which was an unusually close approach, though not the closest possible, for the distance had been only '373 at the opposition in 1845, as it will be again in 1924, these being the two minimum distances during the two centuries 1800- 2000. The opportunity was made use of by Mr. David Gill for the determination of the solar parallax, as we shall presently relate, and at this apparition of the planet its two satellites were dis- covered by Asaph Hall. Another incident of the year 1877 was the search for the sup- posed intra-mercurial planet (Vulcan) at the instigation of M. Le Verrier. It had happened not infrequently that a spot or some other marking had been seen on the sun, which the observer assumed might have been a planet whose orbit was within that of Mercury. 13