n6 HISTORY OF THE [1850-60 careful comparison with star charts, and he lamented that this country possessed no charts at all comparable with the Berlin series, a defect so markedly brought to light in the history of the discovery of Neptune. Hind worked at the observatory established by George Bishop, who was for many years Treasurer of the Society, in the grounds of his house, South Villa, Regent's Park, on the site now occupied by Bedford College. He at first used the Berlin charts, but finding that they were deficient of the fainter stars, nothing below the tenth magnitude being shown, and that they did not include the whole of the region about the ecliptic, he set himself to make another set of charts containing all stars down to the eleventh magnitude within 3 of the ecliptic, and with the aid of these was able to make further discoveries. This total was ten planets, eight up to the time when he received the Medal, and two shortly afterwards ; but as he was then appointed Superin- tendent of the Nautical Almanac, he was compelled to discontinue active observing work. With the exception of three found by Pogson at Oxford during 1856 and 1857, no further minor planets can be credited to any observer in this country. In other directions there was great activity in these years in the construction of star charts and catalogues : 1850 was the epoch of the British Association Catalogue, due to the indefatigable labours of our energetic Fellow, Francis Baily, which recorded every star down to the sixth magnitude of which reliable observa- tions could be found ; 1855 must always remain a memorable date to astronomers, as being the epoch of the Bonn Durchmusterung, generally called the B.D., which far excelled all previous star atlases. Originally carried out by Argelander from the N. Pole to 2 beyond the Equator, and continued by his successor Schonfeld down to 23 south of the Equator, it showed every star down to magnitude gj, and was for many years, in fact until, to some extent, super- seded by modern photographic charts, invaluable for comet search- ing and similar tasks. The intensive scrutiny for minor planets on the Continent gave rise to the production of beautiful ecliptic charts by Chacornac and the brothers Henry. There was one astronomical advance of prime importance made about this time, to which it is not easy to fix a precise date, Schwabe's proof of the periodicity of sun-spots. He, it is true, announced in 1844 that he had got indications of a ten-year period, but the announcement excited no attention and apparently met with little belief. In 1850, Humboldt, in the third volume of his Kosmos, gave a table of the sun-spot statistics as observed by Schwabe from 1826 to date, in which the periodicity was so evident that it could not be overlooked. Schwabe was awarded the Gold Medal in 1857, the President being M. J. Johnson, the Radcliffe
