THE HONGKONG GOVERNMENT GAZETTE, 17TH NOVEMBER, 1877.
513
3. Captain SUMMERS' method of ascertaining the ship's position has largely increased the value of correct"Greenwich Time."
4. Under these circumstances, the establishment of a Time-Ball at Hongkong will, I am sure, be welcomed by the shipping interest. At present the Masters of merchant ships are tempted either to take their chronometers to a watchmaker at Victoria, which is pretty sure to alter the rate or to work with the old "error" corrected perhaps by their error in making their land-fall at Hongkong.
5. To have correct "Greenwich Time" made to them every day at 1 P.M., would give them the correct errors of their chronometers, and during their stay in port, if long enough, they would ascertain the rates also, or a sea rate from the last port touched at where they were supplied with "time."
6. At certain periods of the year, the Coasts of China and Japan are enveloped in fogs, but peeps of the sun with a fair horizon are generally to be obtained at some time during the day. A serious doubt as to the accuracy of the "Greenwich Time," say to from 10 to 15 miles, would often prove most embarassing when the Master is relying almost entirely upon "Summers' Method" for safety, whereas if the Greenwich Time can be relied on to have a margin of error not exceeding say from 3m. to 5m. the passage can be made with great safety and rapidity.
7. At Shanghai, the Time is given once a week by the Senior Naval Officer (English), who drops a Ball from the masthead at 1 P.M. every Tuesday. This is of service, and is better than the absence of any such aid to navigation which we find at Hongkong, but it is liable to serious error. This description of Time-Ball is a useful check to mistakes in the observations of the Masters of merchant vessels taken on shore for rating their chronometers, but it would not be wise for any one to rely on it entirely, and yet I have no doubt many Masters do so.
8. A mistake on the part of the Officer who has charge of dropping the Ball is very easy to make, and yet a mistake of one minute involves a mistake on the Longitude first ascertained after leaving the Yangtze of fifteen miles! Fifteen miles is a wider offing than a merchant steamer generally allows herself outside of any dangers on her way; the mistake of " one minute" made by the Navigating Sub-Lieutenant gun-vessel at Shanghai (or by his deputy if he is absent) in dropping the Ball, may evidently, therefore, result in the loss of the merchant vessel depending upon his accuracy for her
Greenwich Time.”
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9. I dwell upon this matter at some length, because if a Time-Ball is established at Hongkong, it very probable that steamers bound from thence to Shanghai or Foochow and back will rely entirely upon the
error and rate” obtained at Hongkong by aid of the Ball there, and it will be very necessary, therefore, that every precaution be taken to ensure absolute accuracy in the dropping of the Ball. Mistakes are sometimes made, and are unavoidable, but a mistake when made is almost certain to be known to the Observer in charge in a properly established Observatory, and I believe the best course to pursue is to hoist the Ball again immediately and drop it at 2 o'clock.
10. Immediate attention is thus attracted. A prompt acknowledgment of the error and a prompt reparation is the only course open to the Superintendent.
11. Very little is known of the Tides and Currents round Hongkong, and vessels approaching from the South not only find no friendly lights to welcome them and lead them into safety, but are informed by the "Sailing Directions," page 79, "that the tides round the Island are irregular." Under these circumstances, as a last resource in thick weather, the mariner studies his charts to see if the soundings South of Hongkong afford, in thick weather, any useful aid, and unfortunately they do not.
12. I suggest, therefore, that an Automatic Tide Guage be promptly set up at Cape d'Aguilar (or at Waglan if the light is ever placed there) under charge of the Lighthouse Keeper, and that when the Gap Rock Light is commenced, a record of the Direction and Rate of Tides be promptly commenced and carefully made there in addition to an Automatic record of the Rise and Fall.
13. When Lighthouses on "Waglan" and the "Gap" are lit, when a Time-Ball is dropped daily in sight of the Shipping in Victoria Harbour, when the Rise and Fall, Set and Rate of the Tides and Currents in the group and to the Southward of it have been ascertained and the knowledge made available to Navigators, a threefold, and at present an apparently well-deserved, reproach will be removed from Hongkong.
His Excellency
THE GOVERNOR,
&c.,
&c.,
&c.
I
am,
Sir,
Your obedien: Servant,
ALFRED P. Ryder, Admiral, Commander-in-Chief.