GOVERNMENT NOTIFICATION.—No. 80.
HONGKONG.
PROPOSED OBSERVATORY.
The following is published for general information.
By His Excellency's Command,
Colonial Secretary's Office, Hongkong, 25th February, 1882.
M. S. TONNOCHY, Acting Colonial Secretary.
HONGKONG, 24th February, 1882.
MY DEAR GOVERNOR,-Having devoted my spare evenings during the last two months to a little scientific work which will be of use to the Colony-namely, a precise determination of the latitude of Mount Elgin-I have much pleasure in sending Your Excellency the accompanying short account of my work and its results, as you will doubtless be glad to place such information on record, for future reference, and as an appendix to my Report of last year.
I am, Dear Sir,
Yours very faithfully,
H. SPENCER PALMER.
His Excellency, Governor Sir JOHN POPE HENNESSY, K.C.M.G.
ON A DETERMINATION OF LATITUDE AT MOUNT ELGIN, IN THE KAU-LUNG PENINSULA, BY MAJOR H. SPENCER PALMER, R.E., F.R.A.S.
In the scheme for the proposed Hongkong Physical Observatory which I drew up last year for the information of His Excellency the Governor, it was explained that astronomical observations in this island would pretty certainly be vitiated by deflection of the spirit-levels caused by the neighbouring hill masses; and this was adduced as one reason for favouring a site at Kau-lung, where the conditions—at least above ground-give no cause for apprehending sensible errors of that kind.
For various reasons, Lieutenant-Commander GREEN, of the United States' surveying-ship "Palos," whose scientific mission I described in the same paper, was obliged, on his arrival here in September last, to establish his own observing station on this shore. But he was fully alive to the weight of the objection explained above; and subsequently, when we were speaking together on the matter, he was good enough to offer to lend me one of his instruments for a month or two, in order that I might myself make a separate determination of latitude on Mount Elgin. With this obliging offer I gladly closed, feeling as I do the importance of having the latitude of the proposed Observatory site established with the highest accuracy possible, and under conditions free from the uncertainty which must affect any determination on this side of the harbour; while the fact that, relying on Lieutenant-Commander GREEN's expected visit, I had omitted from the Observatory scheme provision for a latitude instrument left no room for doubt as to the wisdom of accepting his offer and devoting some time and trouble to a determination which should be precise and final.
The operations and results are described in the following notes and tables.
Observing Station.-The observing station is near the western edge of the eastern of the two eminences which are together called Mount Elgin-the same on which it is proposed to erect the main building of the future Observatory. It is marked by a small pier, erected for the support of the instrument.
Instrument. The instrument used was a portable transit-instrument, adapted for use also as a zenith-telescope. It was made in America, by Messrs. ALVAN CLARK & SONS, for the United States' Transit of Venus Commission, 1874, and it is numbered 1505. This instrument is of the Diagonal form, which I believe originated in Russia, and in which the rays of light, instead of passing straight from the object to the eye end of the telescope, are bent at right angles by a prism fixed at the junction of the tube and axis, and so pass out at one of the pivots. The great advantage of this form of construction is that the observer occupies the same position no matter what be the zenith-distance of the star under observation. Its disadvantages, which are few, apply more to its use as a transit-instrument than as a zenith-telescope. Other advantages of this instrument are its easily manageable reversing apparatus and its remarkable stability under reversal.
The telescope has an object-glass of 2.5 inches aperture, and a focal length of about 30 inches; and the eye-piece commonly used magnifies about 50 diameters. Stars down to the seventh