Page:History of the Royal Astronomical Society (1923).djvu/225

 1870-80 ] ROYAL ASTRONOMICAL SOCIETY 197 whose superintendence the reduction of the British observations had been made at Greenwich, presented a result of the discussion of the solar parallax from observations made by British Colonial observers beyond those given in the Parliamentary Report, which produced a result considerably larger, lying between 8 "-82 and 8 "-88 ; and in the supplementary number there is to be found the values derived from the photographs, which were absurdly small and quite inadmissible, alternative figures being 8 "-240 and 8 "-082. A value of this fundamental constant of Astronomy derived from observations of Mars at the opposition in 1877 was communicated to the Society in December of that year by Mr. Maxwell Hall, an amateur astronomer in Jamaica, who had determined the parallax by means of the displacement of the planet in right ascension when far east and far west of the meridian, measured by transits of the planet and comparison stars over the wires of a 4-inch equatorial. The resulting parallax was 8 "-79, with a probable error of dbo"-o6o. The parallax found by Mr. Gill from his observations of Mars at Ascension was 8"-78o"-oi2. Opportunity had been taken by several persons of the close approach of Mars at the 1877 opposition to make observations of its surface features, and several communications of this kind will be found in the Monthly Notices of this period Mr. N. E. Green, an artist and amateur astronomer, had made a journey to Madeira for the purpose. His drawings of the planet, made in 1877 August and September, were presented to the Society in November and are published in volume 44 of the Memoirs. The outer satellite of Mars was observed in England by various observers. There was a transit of Mercury of 1878 May 6, which was observed by many persons, features specially looked for being a halo of light round the dark disc of the planet in transit, and a white spot said to be sometimes seen at its centre, which were discussed at some length at the meeting in May. It appears that these were considered important circumstances, for though no time observations were made at Greenwich owing to the state of the sky at ingress and egress, the planet in transit was examined at the Royal Observatory for the physical features above mentioned.* Other communications to the Society that may be specially noted are two papers on the Lunar Theory by Professor Adams, and three by Mr. Neison. Mention may also be made of the visit of Professor Rutherfurd, of New York, in 1878 May, who presented some photographs of the sun taken in 1871, showing granulations or rice grains, for the purpose of correcting to some extent a statement made at an earlier meeting that certain photographs taken by M. Janssen were the
 * M.N., 38, 397-