A transit of Mercury took place on November 7, and lasted about four hours. It was well observed, but was not expected to yield results of importance. The last transit occurred in 1907, the next two are due in 1924 and 1927.
The very small ninth satellite of Jupiter, of the nineteenth magnitude, was photographed for the first time, on July 21, by Mr. Seth B. Robinson. Its orbit is elliptical, and its motion retrograde, with a period of about three years.
Several of the satellites of Saturn have been shown to have equal periods of rotation and revolution, like our moon.
The Astronomer Royal, Dr. F. W. Dyson, lecturing at the Royal Institution, on April 24, said that the solar system was near the middle of a finite group of stars, the limiting distances of which were from 1,000 to 10,000 parsecs. (By "parsec" is meant a parallax of one second, corresponding to a distance equal to 206,265 times that of the sun.) About 88 per cent. of the stars brighter than 10.5 magnitude are from 20,000,000 to 150,000,000 times as far off as the sun, and of these 90 to 95 per cent, are intrinsically brighter, 87 per cent. being fifty times as bright, or more. Red stars are very distant; yellow stars, on the whole, are nearest, and the distance increases as the colour changes to blue or orange. The thinning out in the number of stars at very remote distances is conspicuous.
Professor E. W. Brown, addressing the Cosmical Physics section of the British Association, spoke of his work on the motion of the moon, which had occupied him for twenty years. All gravitational forces have been taken account of, and the improved tables will be made use of in the Nautical Almanac for 1919, the intermediate issues having already been printed. A few residual corrections remain, the origin of which may be due to electrical or other forces.
A selenium photometer for determining stellar magnitudes, devised by Mr. Joel Stebbins, and improved by Rosenberg of Tübingen, enables a magnitude to be determined within about 1-500th, after a couple of minutes' exposure, using a 5-inch refractor. By the ordinary method the process is very much more tedious and less accurate.
The Canadian reflector of 72-inch aperture will be ready in about two years, and will be erected on a hill seven miles north of Victoria, B.C. It is designed for spectrographic work and for photographing star-clusters and nebulæ. Its focal length of 30 feet can be increased to 108 feet by a Cassegrainian combination.
The first comet of the year (1914 a) was discovered on March 29, by Kritzinger, in Ophiuchus; the second (1914 b) by Zlatinsky, on May 15, in Perseus, and the third (1914 c) by Neujmin, on June 29. The thirty-third return of Encke's comet was observed in November; its perihelion is now nine days later than if the motion had continued as in 1848.
An aerolite, one of the largest ever known to have fallen in Great Britain, descended in a field at Appley Bridge, near Wigan, on October 13. The weight of the two principal fragments was 28 lb. 13 oz., and it measured a little over 9 inches in each dimension. It was composed of olivine 63.43 per cent., enstatite 31.5 per cent., pyrites and metallic matter 5.07 per cent., and showed traces of superficial fusion, but presented no exceptional features apart from its size.