AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 131 
planation of the formation of such remarkably shaped reefs as the Nanuku 
and Nukusemanu Reefs (Plate 18), from the denudation and erosion of 
an extended ridge or line of the summits of independent islands, elevated 
at the time when the great masses of ancient limestones were raised to 
various heights perhaps up to one thousand feet. 
The Great Sea Reef (Plate 1) appears on the chart as the continuation 
of the chain of which the Yasawa group of islands are the only rem- 
nants, and it may be that it represents its eastern continuation after its 
denudation and erosion, and transformation into a submarine platform 
for the growth of corals. Similarly the reefs extending to the east of 
Vanua Levu towards the Yasawa group may be the western extension of 
a range of which Sesaleka Peak and Yendua Islands formed prominent 
points. 
GENERAL SKETCH OF THE FIJI ISLANDS AND CORAL REEFS. 
I went to the Fijis under the impression that I was to visit a charac- 
teristic area of subsidence ; for according to Dana and Darwin there is 
no coral reef region in which it is a simpler matter to follow the various 
steps of the subsidence which has taken place. Dana, in his last dis- 
cussion ? of the coral reef question, states that it is impossible to find a 
better series of islands than the Fijis to illustrate the gradual changes 
(brought about by subsidence) which take place in transforming a yol- 
canic island with a fringing reef to one with a barrier reef, or to one with 
an encircling reef ring, and finally to one in which the interior island 
has disappeared and has left only a more or less circular reef ring. For 
these reasons one of the Fiji atolls promised to be an admirable location 
for boring and settling the question of the thickness of the coral reef of 
an atoll. 
My surprise was great, therefore, to find within a mile from Suva an 
elevated reef about 50 feet thick, and 120 feet above the level of the sea, 
the base being underlaid by what is locally called ‘ soapstone,” *? a kind 
of volcanic mud. The western extension of this reef can be traced at 
1 Am. Journ. of Science, Vol. XXX., August and September, 1885. Dana says: 
“The large Feejee group bears abundant evidence of subsidence in its very broad 
reef grounds, barrier islands, and atolls.” 
2 The “soapstone” is largely composed of volcanic débris, mixed with tests of 
Foraminifera, Pteropods, and Mollusks. Brady (Q. J. Geol. Soc. London, 1888, Vol. 
XLIV. p. 1) considers the Rhizopod fauna such as one would expect from a depth 
of 150 to 200 fathoms. 
