Page:History of the Royal Astronomical Society (1923).djvu/250

 2i8 mSTORY OF THE [1880-1920 to the Struve-Peters constants be given in an appendix up to the end of 1906. An abstract of the Nautical Almanac, called Part I., " containing such portions as are essential for navigation," had been published at the request of the Shipmasters' Society, the earliest one being for the year 1896 ; price one shilling. This little almanac contained the monthly part of the big one unaltered, so as to save the expense of setting up the type afresh, though this involved giving sailors various things they did not want. Also the noon-ephemerides for Venus, Mars, Jupiter, and Saturn, the eclipse section, and a few other items. Though most useful to sailors, it was felt that this publication was capable of improvement. In 1910 October the Admiralty therefore addressed the Council of the Society, pointing out that the necessity of frequently checking the position of a ship by observations was generally recognised, and that it was thought that the labour of computing should be still further reduced, while matter of no use to the seaman should be got rid of. A Committee was appointed, including Mr. Cowell, who had not long before succeeded to the post of Superintendent on the retirement for age of Mr. Downing. This Committee reported in 1911 February. In their recommendations the general prin- ciple was followed of only giving the data to that degree of accuracy which can be made practical use of in the best observations at sea. This was taken as o s -i and o'-i, with variation in one hour to o s -oi and o'-oi respectively, though some exceptions to this rule were made. The right ascension of the mean sun, the declination of the sun, and the equation of time to be given for every two hours, so that no interpolation would be necessary. These alterations were carried out from 1914.* In this new " Part I." almost nothing is taken unaltered from the real Nautical Almanac except the data referring to eclipses. At the Annual General Meeting in 1911 February, Gill, after delivering the Presidential Address on presenting the Gold Medal to Dr. P. H. Cowell for his contributions to the Lunar Theory and Gravitational Astronomy, delivered a second address on some points connected with the subject-matter of the first one.f After considering which kind of observations of the moon are particularly wanted for the improvement of the Lunar Theory, and which might be discontinued, he turned to the subject of the Nautical Almanac office. He pointed out, that whereas two out of the three great subdivisions of Astronomy, astrometry and astro- physics, are dealt with in the two national observatories adminis- tered under the Admiralty, the study of the third subdivision, t M.N., 71, 380-385.
 * For further particulars see The Observatory, 35, 245.