Ch. V. 
OF CORAL-REEFS. 
123 
monly attained by matter thrown up by the winds 
and the waves of an open sea. If we draw a line 
joining the external atolls of that part of the Low 
Archipelago in which the islands are numerous — the 
plan always adopted — the figure will be a pointed 
ellipse (reaching from Hood to Lazaref Island), of 
which the longer axis is 840 geographical miles, and 
the shorter 420 miles : in this space, 1 none of the 
innumerable islets, united into great rings, rise above 
the stated level. The Gilbert group is very narrow, 
and 300 miles in length. In a prolonged line from 
this group, at the distance of 240 miles, is the 
Marshall Archipelago, the figure of which is an 
irregular square, one end being broader than the 
other ; its length is 520 miles wittr an average width 
of 240 : these two groups together are 1,040 miles in 
length, and all their islets are low. Between the 
southern end of the Gilbert and the northern end of 
Low Archipelago, the ocean is thinly strewed with 
islands, all of which, as far as I have been able to 
ascertain, are low : so that from nearly the southern 
end of the Low Archipelago, to the northern end of 
the Marshall Archipelago there is a narrow band of 
ocean more than 4,000 miles in length, containing a 
1 Metia or Aurora Island has been upraised ; but it lies N.E. of 
Tahiti, and in the map appended to this volume is close without 
the line bounding the space here referred to. I shall have occasion 
hereafter to make some remarks on the supposed slight elevation (of 
about three feet) of the atolls of the Low Archipelago, subsequently 
to their original formation. [Other cases of upheaval have since been 
recorded. See Appendix II.] 
