Entering the courtyard--an enclosure some eighty feet deep by ninety feet in extreme breadth--by the great gate, we see before us Flamsteed House, the original building of the Observatory. Flamsteed's little domain was only some twenty-seven yards wide by fifty deep, and for buildings comprised little beyond a small dwelling-house on the ground floor, and one fine room above it. This room--the original Greenwich Observatory--still remains, and is used as a council room by the official Board of Visitors, who come down to the Observatory on the first Saturday in June, to examine into its condition and to receive the Astronomer Royal's report. The room is called, from its shape, the Octagon Room, and is well known to Londoners from the great north window which looks out straight over the river between the twin domes of the Hospital. In Bradley's time, about 1749, the first extension of the domains of the Observatory took place to the south and east of the original building, the direction in which, on the whole, all subsequent extensions have taken place, owing to the fact that the original building was constructed at the extremity of what Sir George Airy was accustomed to call a 'peninsula'--a projecting spur of the Blackheath plateau, from which the ground falls away very sharply on three sides and on part of the fourth. The Observatory domain at present is fully two hundred yards in greatest length, with an average breadth of about sixty. Nearly the whole of this accession took place under the directorates of Pond and Airy. The present instruments are, therefore, as a rule, the more modern in direct proportion to their distance from the Octagon Room--the old original Observatory. There is one notable exception. The very first extension of the Observatory buildings, made in the time of Halley, the second Astronomer Royal, consisted in the setting up of a strong pier, to carry two quadrant telescopes. The pier still remains, but now forms the base of the support of the twin telescopes devoted to the photographic survey of the heavens for the International Chart.