544
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dient is broken granite. Even the bricks made of Canton River mud contain iron, though to a less extent than the granite. I suggest that an analysis be made of the limestone of the White Mountain Range, near Canton, which, if found sufficiently free from iron, might be imported for our purpose, and used both for the masonry and the concrete, if not too costly. A fine concrete, of suitable quality, might be made with washed gravel of this island, i.e., the common decomposed granite (taking care to select a coarse, gritty sample), dug from a nullah side, and washed until only the quartz particles remain. This of course would be expensive. I have little doubt, however, that, on careful inquiry, it will be found neither very difficult nor very costly to procure, near at hand or somewhere on the coast, a material that will fulfil all requirements.
The same rule as regards the exclusion of iron must be followed in every detail of construction. All nails, locks, keys, hinges, bolts, hooks, gratings, pipes, &c., should be of copper, brass, or zinc; and it is important to bear in mind that the copper articles ought to be of European manufacture, as those made in China contain a large percentage of iron. The Reverend M. DECHREVENS, S.J., director of the Zi Ka Wei Observatory, with whom I have entered into correspondence, and to whom I am indebted for some valuable suggestions relating to the Magnetic building, as well as for plans and photographs of his own establishment, is emphatic in his caution on this point, and recommends me "n'employer 'pour les portes, les fenêtres, les jonctions, etc., que du cuivre, et autant que possible que des objets, 'clous, gonds, serrures, charnières, venues d'Europe, ne pas se fier aux Chinois pour cela: tous leurs 'objets de cuivre contiennent une grande proportion de fer. Tout le cuivre qui est entré dans notre des ouvriers 'salle magnétique, et principalement tout ce que nous avons été obligé de faire fabriquer par 'Chinois, à été essayé au magnétomètre avant d'être accepté, et rejeté invariablement dès qu'il produisait 'sur l'aimant une déviation de quelques minutes d'arc à un pied de distance."
CL
The Barograph, it may also be remarked, must, if possible, have no iron about it, as it will be mounted in the same chamber with the Magnetograph. The instrument-pillars, which should be capped with slabs of slate or marble, may be made from the same material as that of the building itself; but they cannot be built until the instruments themselves, or their exact dimensions, have been received.
For protection against lightning, a single conductor, carried by a post 25 feet high, erected anywhere near the building, will answer.
For the Dip-circle, a small pavilion and pier will have to be erected, in a position well removed from the other magnets, such as the ground outside the astronomical building. This, however, as well as the provision, also above ground, to be made for the Unifilar Magnetometer, may be considered later on.
In the meantime, there will be nothing to prevent the two main buildings from being proceeded with as soon as the working drawings and estimates can be prepared.
IV. Tidal Observations.
There is one instrument which, though referred to in His Excellency the Governor's despatch already quoted from, has not yet been mentioned in this report, and which might with advantage be added to the outfit, namely, a Tide-gauge, for the purpose of determining the laws of the tides at Hongkong, certain phenomena of which, such as the diurnal and other inequalities, are peculiar and, I believe, but little known or understood. An autographic tide-gauge might be set up in a chamber constructed for the purpose near the Tsim-shá-tsui Police Station, and attended to each day by the man in charge of the Time-Ball and Weather-Signals. Such a gauge, of Sir W. THOMSON'S pattern, would cost about £95.
Admiral RYDER suggested, in 1877, that an automatic Tide-gauge should be set up at Cape D'Aguilar, and placed in charge of the lighthouse-keeper there. This is most desirable, as a means of establishing the direction and rate of the tides, and I recommend that it be carried out unless the engineering difficulties prove too serious, in which case a suitable spot might perhaps be found on one of the headlands nearer to Stanley. A less expensive gauge, of NEWMAN's pattern, and costing about £50, would serve for this station.
V. Staff.
Notwithstanding that so large a proportion of the various instruments will be of self-registering patterns, the routine work of the observatory will, nevertheless, be very considerable. Even autographic instruments require periodic attention, most of them at least once daily. Time-determinations should be made certainly three or four times a week, and these necessitate a considerable amount of observing by night and computing by day. Frequent periodic magnetic observations for absolute values, which are tedious, difficult and highly complicated, will also have to be made and computed. Constant attention must be given to the adjustments of the extensive and miscellaneous apparatus, to winding and regulating clocks, ascertaining the errors of the instruments, and keeping all clean and in good order.
A good deal of extra work will also devolve upon the Department during several months of the year, in collecting information respecting typhoons.
The regular clerical labour will consist mainly of entering the observations and calculations in the books and forms for that purpose, transcribing and filing the automatic records, compiling weather exchanges and storm data, abstracting typhoon-logs, preparing periodical reports, accounts, &c., and general correspondence.
The Director of the Establishment should be, if possible, some one recommended by the Astronomer-Royal. No one could be more desirable than an ex-assistant of the Royal Observatory. I do not think we can expect to get a competent person for less than $300 per mensem. He should have, as First assistant, a practical man, chosen with great care—a man able to observe and compute, acquainted with the mechanical details of the instruments, and competent to execute, or at least direct, ordinary repairs. An assistant of this kind could probably be got from amongst the non-commissioned officers of the Ordnance Survey Companies of the Corps of Royal Engineers, a very valuable body of men. He should receive a salary of $120 per mensem. To the Royal Engineers we may also look for the Second assistant, who should be a good photographer, and be deputed to attend specially to the Magnetic instruments. Arrangements might, no doubt, be made to procure for him a month's training at the Greenwich Observatory in the routine of the magnetic work. He might be paid $75 per mensem.
Clerks, of whom two at least will be needed, can be obtained locally. They should be very trustworthy and accurate men. The rest of the employés may be Chinese, namely, a caretaker, to have general charge of the premises; a gardener, for the grounds; coolies, to act as messengers, keep the buildings and premises clean, trim lamps (there being, most unfortunately for the Observatory, no gas at Kau-lung), &c.; and night watchmen; also an intelligent man to attend to the Time-Ball, Weather-Signals and Tide-Gauge at Tsim-sha-tsui, and who should, if possible, be accommodated in the Police Station.
VI. Finance.
It is now possible to form an idea of the first outlay and the yearly cost of maintenance for the whole establishment as above designed, which probably will not differ much from the following, though the estimates for the buildings can only be considered as approximate, no detailed drawings and calculations having yet been made.
Astronomical Apparatus, £500 say $2,667
Meteorological do., 397 2,117
Magnetical do., 424 2,262
Time-Ball do., 400 2,133
Two Tide-Gauges, 145 773
Two ROBINSON's Anemometers, for Victoria Peak and Cape D'Aguilar, " 12 64
Freight and Insurance of the above to Hongkong, 100 533
Main Observatory Building and Out-houses, Furniture and Fitments, 12,900
Magnetic Basement, 500
Connecting Observatory with the Kau-lung- Expenditure on the Grounds and Approaches, Fencing, &c., Telegraph Line to the Time-Ball, including 4,500
Cable, say, 1,600
and cost of Speaking-Instrument, &c., Miscellaneous Erections, as for the Time-Ball, Weather-Signals, Tide-Gauges, Meridian-Mark, and parts of the Meteorological and Magnetic Apparatus, 250
an-má-ti Telegraph Line, 250
Lamps, Observing Seats, &c., 3,000
Total Prime Cost (Approximate), $83,600 or £6,300
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