His immediate successors did much less in this field, though Bradley's observations were published, long after his death, as a catalogue of 3222 stars, in some aspects the most important ever issued. Pond, the sixth Astronomer Royal, restored catalogue-making to a prominent place in the Greenwich routine, and his precedent is sedulously followed to-day. But each of these was confined to about 3000 stars. The necessity has long been felt for a much ampler census, and Argelander, at the Bonn Observatory, brought out a catalogue of 324,000 stars north of South declination 2°, a work which has been completed by Schönfeld, who carried the census down to South declination 23°, and by the two great astronomers of Cordoba, South America, Dr. Gould and Dr. Thome, by whom it was extended to the South Pole. These last three catalogues embrace stars of all magnitudes down to the 9th or 10th; but certain astronomers had endeavoured to go much lower, and to make charts of limited portions of the sky down to even the 14th magnitude. From the very earliest days that men observed the stars, they could not help noticing that 'one star differeth from another star in glory,' and consequently they divided them into six classes, according to their brightness--classes which are commonly spoken of now as magnitudes. The ordinary 6th magnitude star is one which can be clearly seen by average sight on a good night, and it gives us about one-hundredth the light of an average 1st magnitude star. Sirius, the brightest of all the fixed stars, is called a 1st magnitude star, but is really some six or seven times as bright as the average. It would take, therefore, more than two and a half million stars of the 14th magnitude to give as much light as Sirius. It is evident that so searching a census as to embrace stars of the 14th magnitude would involve a most gigantic chart. But the work went on in more than one Observatory for a considerable time, until at last the observers entered on to the region of the Milky Way. Here the numbers of the stars presented to them were so great as to baffle all ordinary means of observation. What could be done? Just at this time immense interest was caused in the astronomical world by the appearance of the great comet of 1882. It was watched and observed and sketched by countless admirers, but more important still, it was photographed, and some of its photographs, taken at the Royal Observatory, Cape of Good Hope, showed not only the comet with marvellous beauty of detail, but also thousands of stars, and the success of these photographs suggested to her Majesty's Astronomer at the Cape, Dr. Gill, that in photography we possessed the means for making a complete sky census even to the 14th magnitude.