THE HONGKONG GOVERNMENT GAZETTE, 3RD SEPTEMBER, 1881. 805
side of the island. A site in many respects suitable might be chosen on the west side, in the neigh- bourhood of Pok-fú-lam, but this would have the disadvantage of being a long way from town, and at a somewhat inconvenient altitude. Another drawback which it would possess, and which, indeed, holds. good as to sites generally in the island, is that the attraction of the abrupt adjacent hill-masses would undoubtedly affect the spirit-levels of the instruments, a point not to be overlooked when choosing a site for an observatory that may hereafter attain scientific importance.
On the whole, therefore, I concur in the Surveyor-General's opinion that Mount Elgin affords the best available site for the Observatory. From that point, the Hongkong hills in the south shut out no more than 4° or 5° of sky, and Victoria Peak itself has an elevation of only about 7°.
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The Time-Ball might be erected on any commanding point which fulfils the indispensable condition of being well seen from end to end of the harbour. Certain conditional rights, the exact scope of which I have not been able to ascertain, are held by the War Department over the plot of land, partly occupied by the Tsim-shá-tsui Police Station, which seems the natural place for the time-ball mast. The War Department also hold the high ground of the southeastern promontory. I understand that the Police Station will shortly be moved a little further back on the plateau which it now occupies, so as to clear the War Department limits. The best plan, in that case, will be to let the small building and mast for the Time-Ball be made an adjunct to the Police Station. The ball should be a large one, eight or nine feet in diameter, and be painted with broad bands of white and bright red. Building. The building for the Observatory must contain a general office and computing room, an office for the Director, a room for the mean solar clock, chronograph, batteries, &c., and on either side a wing room, one for the transit-instrument and sidereal clock, the other for the additional apparatus, such, for example, as Seismic instruments, which is pretty certain to be procured before very long. I propose also to provide a small room for the Electrograph, which will be referred to farther on. I have added, at Mr. BOWDLER'S suggestion, an upper storey, to be appropriated as quarters for the Director. I recommend that the building be constructed of red bricks, the walls of the lower storey being made 1 ft. 9 in. thick, and those of the upper storey 1 ft. 2 in. thick. The rooms should be 15 feet high, from floor to ceiling, and the roof be made as flat as possible, in order that it be utilised for some of the meteorological apparatus. Especial care must be given to protection of the building against lightning, for which purpose one conductor should be placed at each angle of the main block, and the points carried at last eight feet above the parapet, the earth ends being sunk below ground until permanently damp soil is reached.
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In laying out the building on the ground, it will be important to obtain accurate orientation, for which purpose I suggest that Polaris be observed with a theodolite at one of its culminations, and a meridian line carefully marked at the observation. The transit-room will need vertical shutters about two feet wide, opening in the north and south walls from a height of four feet above the floor, and extending to the roof; also roof-doors of the same width, so that there may be a clear view of the meridian from the south to the north horizon. The collimator may be placed on a brick pier about fifteen feet to the north of the transit-room, a small room or hut six or seven feet square being built over it, for protection from the weather. It should be approximately horizontal with respect to the transit-instrument.
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Piers, isolated from contact with the surrounding soil or any parts of the building, will be needed for the transit-instrument, the electrograph, the collimator, and each of the two clocks. These should be built of red bricks, in cement, and be carried down to firm ground, at a depth of not less than four feet in any case, there resting on good foundations of cement concrete. The largest will be those for the transit-instrument and electrograph, which may measure about six feet by three feet. For the clocks the dimensions will be very much smaller. All of them had better be left unfinished at the floor-level until the instruments and clocks arrive.
A building on a plan somewhat as shown in the accompanying tracing will probably answer as well as any for the present purposes of the Observatory. Lest it be thought that the space provided is somewhat more liberal than is necessary, it may be well to bear in mind the great heat of the summer weather, as well as the facts that ample room will be needed for presses for stores, stationery, records, &c., and that the requirements as to space in an establishment of this kind are certain to grow year by year. If at a future time it should be decided to increase the equipment, the east and west wings could be extended so as to accommodate a Photoheliograph for the record of sun-spots, as suggested by His Excellency the Governor, and an Equatorial telescope. It would be necessary, in this case, to raise the equatorial sufficiently high to obviate any serious interruption of the sky view by the upper storey of the main block; and, for architectural symmetry, the photoheliograph might be similarly raised. But, if a Siderostat in connexion with a fixed telescope should be preferred for gazing purposes to an equatorially mounted instrument, no such elevation would be needed. A building of the kind above suggested would probably cost, with piers, &c., about $10,500, to which $500 must be added for furniture and fitments. A small additional building, to contain quarters for a caretaker, servant and coolies, with a store, workshop, kitchen and other offices, and connected with the main edifice by a covered way, would cost say $2,400 more. Both of them may be at once designed in detail, and proceeded with, should the scheme here proposed receive the approval of the Government.