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CHAPTER I
The Area
All previous British atomic tests have
taken place in Australia, either at Maralinga, in the South Australian
desert, or in the small uninhabited Montebello Islands off the
north-west coast. However, for testing weapons of the scope involved in
Operation Grapple there could be no question, from the safety point of
view, of using these continental proving grounds. Therefore, a
completely new base had to be found which would conform to certain
essentials. The base had to be remote from any inhabited area; have
favourable wind and weather conditions for air and sea operations; be
accessible (even if distant) from a source of supply, and have a
suitable harbour for landing these supplies; and finally, be suitable
for the construction of an airstrip which could be used by Valiants and
other large aircraft.
An area in the Pacific seemed to be the
inevitable choice and after careful consideration, and in the light of
surveys made by a ship of the Royal New Zealand Navy and by aircraft of
the R.A.F., Christmas Island was selected as the base island and Malden
Island as the instrumentation island.
Christmas Island, a part of what are known
collectively as the Northern Line islands, is the largest coral atoll in
the Pacific, although its dimensions are only about 35 miles east and
west by 24 miles at its greatest width. As you can see from the map, the
shape of the island roughly resembles a large lobster claw, the jaws of
which, opening to the northwest, contain a spacious and almost
semi-circular lagoon. In general the elevation is only about 10 feet
above sea-level, but to the east there are sand dunes rising to 20, and
in some places to 40 feet. Surrounding the island is a fringing reef,
several hundred yards in width. There are coconut palms and bush in the
west, but merely a tough prickly grass (unsuitable for cattle) and low
shrubs in the centre, the eastern part being largely bare. The climate
does not encourage the growth of vegetation as the island is subject to
severe droughts which may last many months. At such times only 6 inches
of rain may fall in the whole year, but in other years over 100 inches
have been recorded. Day temperatures vary between 70° and 100°F, but
the Easterly Trade Winds exert a cooling influence so that, despite the
high humidity, the heat is not oppressive. No hurricanes have ever been
experienced in the area.
Beneath the Central Pacific lies a system of
alternative ridges and troughs most of which trend from NW to SE. These
ridges are really submarine mountains rising from the bottom of the
ocean. Where they emerge above the surface they form volcanic islands,
like the Hawaii
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