74 HISTORY OF THE [1830-40 the following decade, was founded on observations made in 1830 and following years. This was a catalogue of 520 stars within 6 of the Ecliptic, observed by Pearson at South Kilworth, Leices- tershire, with a transit instrument and a 3-foot-altazimuth.* Of greater importance than these was the catalogue of 726 stars deduced from observations made at the Cambridge Observatory from 1828 to 1835, which appeared in volume 9 of the Memoirs. This foreshadowed what might be expected, in the way of per- fectly independent catalogues of standard stars, from the Green- wich Observatory under its new director, and was a fitting ending to his work at Cambridge. If we now turn from the public observatories to those of private observers, we find again one great name which stands pre-eminent ; that of John Herschel. The observations of double stars made by him with his 2O-foot reflector at Slough were published in the Memoirs of the Society in eight instalments. Six of these f contain the places of the couples found, 3346 in all. The position angles were up to 1828 July 5 merely estimated ; after that date they were measured by a micrometer, but the distances were estimated throughout the whole series. In the first three papers the position angles are expressed according to the notation used by W. Herschel, the parallel being the zero line and the angles counted from o to 90 in each quadrant. But in the fourth series (presented 1830 April) Herschel used the notation ever since adopted, having found the old system very liable to introduce errors and confusion. Some members of the Council seem to have been alarmed by this innovation ; and the Committee, to whom the paper had been referred, recommended that the old notation should be adhered to. South was, however, requested to consult with Herschel, and, as an old observer of double stars, he was no doubt easily persuaded of the advantages of the new plan. The nebulae and clusters found in the course of HerschePs " sweeps " were formed into a catalogue of 2306 objects for 1830; the single observations being given for each object. About 500 of these objects were recorded for the first time. This catalogue was presented to the Royal Society, and published in the Philoso- phical Transactions for 1833. Our Society's Gold Medal was awarded to Herschel for this work in 1836. Simultaneously with these observations with the 20 -foot reflector, Herschel also made measures of double stars with a refractor of 5-iriches aperture and 7 feet focal length, equatoreally mounted. These measures were published in two papers in the Memoir s.% We may add that another distinguished observer of
- Memoirs, 15, 97-127. t Ibid., 2, 3, 4, 6, 9.
J Ibid., 5, 13, and 8, 37-
