A BRITISH WARTIME CHART SHOWING HONG KONG
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As can be seen from the illustration the chart has a somewhat old-fashioned appearance as it has the radiating lines indicating the 32 directions in the same manner as the Mediaeval Portulan Charts. It would appear that these lines indicate true and not compass bearings as one East to West line meets the point indicating 21° 54' N. on both sides of the chart, also a North line to the south of Hong Kong (not shown on the illustration) has a fleur-de-lis emblem on it; this is the usual symbol to indicate true north.
The scale of the chart is not given, but the sides are graduated at one minute intervals of latitude. These can be taken as Sea Miles in use at that time. The precise length of one degree of latitude was in dispute during the eighteenth century, and lacking other information it is probably safest to assume that the value obtained by Picard in 1669 would have been used. This assumption would give a scale of 1:333,475, with 10 Sea Miles equivalent to 56 mm., 10 kilometres equivalent to 30 mm, and 10 Statute Miles equivalent to 1.9 inches. It should be noted, however, that the Kilometre did not come into use until 1799 and that the Statute Mile was established by an Act of Parliament in 1824.3
The latitudes of the southern point of Macao on the chart is 22° 12′ N., being 14 minutes too far north. The latitude of Canton, at the position of modern Shameen, is 23° 9′ N., being 3 minutes too far north, while Kowloon City at 22° 21' N. is 1 minute too far north. These latitudes are very accurate for the period, but not surprisingly so, considering the fact that the Portuguese had been in the area for more than 250 years, and that as the positions are within the tropics their latitudes could be deduced from the date of the sun at Zenith with the help of the Solar Declination Tables. The small error for Kowloon City is fortuitous, due to surveying errors.4
Regarding the content of the map it is clear from the title that we are faced with a composite map with at least two and possibly three distinct sources. These are 1. A Portuguese Chart 2. A Chinese Chart 3. Possibly original surveys by Hayter or others. The Portuguese influence can be seen in the names "Furado" and "Porado”. The contents of the "Chinese Chart of the Macao Pilots" is not known, but if the maps in the local gazetteer of the Hsin-an Hsien are any indication they are not likely to have been based on accurate surveys.