The prominence work had also to be dropped, partly for the same reason, but chiefly because the atmospheric conditions at Greenwich are not suitable for these delicate astrophysical researches. When the Observatory was founded 'in the golden days' of Charles II., Greenwich was a little country town far enough removed from the great capital, and no interference from its smoke and dust had to be feared or was dreamt of. Now the 'great wen,' as Cobbett called it, has spread far around and beyond it, and the days when the sky is sufficiently pure round the sun for successful spectrum work on the spots or prominences are few indeed. Whether in the future it will be thought advisable for the Royal Observatory to enter into serious competition in inquiries of this description with the great 'astrophysical' observatories of the Continent and of America--Potsdam, Meudon, the Lick, and the Yerkes--we cannot say. That would involve a very considerable departure from its original programme, and probably also a departure from its original site. For the conditions at Greenwich tend to become steadily less favourable for such work, and it would most probably be found that full efficiency could only be secured by setting up a branch or branches far from the monster town. With the older work it is otherwise. So long as Greenwich Park and Blackheath are kept--as it is to be hoped they always will be--sacred from the invasion of the builder; so long as no new railways burrow their tunnels in the neighbourhood of the Observatory, so long the fundamental duties laid upon Flamsteed, 'of Rectifying the Tables of the Motions of the Heavens and the Places of the Fixed Stars,' will be carried out by his successors on Flamsteed Hill. CHAPTER XII THE ASTROGRAPHIC DEPARTMENT The two last departments mentioned, the heliographic and spectroscopic, lie clearly and unmistakably outside the terms of the original warrant of the Observatory, though the progress of science has led naturally and inevitably to their being included in the Greenwich programme. But the Astrographic Department, though it could no more have been conceived in the days of Charles II. than the spectroscopic, does come within the terms of the warrant, and is but an expansion of that work of 'Rectifying the Places of the Fixed Stars,' which formed part of the programme enjoined upon Flamsteed, the first Astronomer Royal, at the first foundation of the Observatory, and which was so diligently carried out by him, the first Greenwich catalogue, containing about 3000 stars, being due to his labours. [Illustration: 'CHART PLATE' OF THE PLEIADES. (_From a photograph taken at the Royal Observatory, Greenwich, with an exposure of forty minutes._)]