DESCRIPTION OF THE PLATES, 
PLATE I. at end of Volume. 
In the several original surveys, from which the small plans on tins 
plate have been reduced, the coral-reefs are engraved in very dif- 
ferent styles. For the sake of uniformity, I have adopted the 
style used in the charts of the Chagos Archipelago, published by 
the East India Company, from the survey by Capt. Moresby and 
Lieut. Powell. The surface of the reef, which dries at low water, 
is represented by a stippled surface with small crosses : the coral- 
islets on the reef are marked by small linear unstippled spaces, 
on which a few cocoa-nut trees, out of all proportion too large, 
have been introduced for the sake of clearness. The entire 
annular reef, which when surrounding an open expanse of water, 
forms an ‘ atoll,’ and when surrounding one or more high islands, 
forms an encircling ‘ barrier-reef,’ has a nearly uniform structure, 
and has been tinted, in order to catch the eye, of a pale blue 
colour. The reefs in some of the original surveys are represented 
merely by a single line with crosses, so that their breadth is not 
given ; I have had such reefs engraved of the width usually at- 
tained by coral-reefs. I have not thought it worth while to 
introduce all those small and very numerous reefs, which occur 
within the lagoons of most atolls and within the lagoon-channels 
of most barrier-reefs, and which stand either isolated, or are 
attached to the shores of the reef or land. At Peros Banhos 
none of the lagoon-reefs rise to the surface of the water ; a few 
of them have been introduced, and are marked by plain dotted 
circhs. A few of the deepest soundings are laid down within 
each reef ; they are in fathoms, of six English feet. 
Fig. 1. — Vanikoro, situated in the western part of the S. Pacific ; 
taken from the survey by Capt. D’Urville in the Astrolabe ; the 
scale is J of an inch to a geographical mile ; the soundings on 
the southern side of the island, namely from 30 to 40 fathoms, 
2 
