Copy.
Enclosure No. 5.
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The Longitude of the Royal Observatory now in use is
7h.36m. 41.25s.E. It was determined by 13 observations of the
Bordeaux radio time signal made simultaneously at the Royal
Observatory, Greenwich and the Royal Observatory, Hong Kong in
September/November 1924, and has been adopted for use since January 1st 1926. No correction was made for the time of
transmission of the radio signal, but it is thought that any
correction to be applied later (on this account, or to bring the
longitude into agreement with the lnternational determination
of Longitudes by wireless telegraphy) will not exceed 0.05s.
Details of the original determination of the longitude
of Hong Kong are to be found in "Telegraphic Determinations of
Longitude in the East Indies, China and Japan 1881-1882′′ in No.
65b of the Hydrographic Office U.S. Navy 1883.
Briefly, Commander Green determined the difference of
Longitude between Madras and Hong Kong as 2h.15m.39.43s., and
the difference of longitude Hong Kong-Vladivostock as lh.10m.52.
07s.
In the absence of any record, it is assumed that the
longitude of the Royal Observatory was calculated as below. It
should be noted that Commander Green's observing station was
Palos pier on the site of the Naval Yard.
h m S
h m s
-1.10.52.07
Longitude Madras 5.20. 59.43E Long Vladivostock 8.47.31.31£ Madras-Palos Pier 2.15. 39.43 VL.-Palos Pier Long.Palos Pier 7.36. 38.85E Long.Palos Pier
h m $
Mean 7.36.39.045E.
Diff. Long.Palos Pier and
Meridian of the Transit
Instrument, Royal Observatory)
7.36.39.245
Hong Kong 3966 feet
Long. Royal Observatory
2.815.
7.36.41.86 E.
determined by triangulation by Public works Department.
The