50 DR. H. B. GUPPY. 
in the concentric ridges of shells and broken corals, which,in the 
instances of Christmas Island and of the neighbouring guano 
islands, mark the successive strips of land gained from the sea. 
The fact that the shells lying on the bare surface of Christmas 
Island have not decayed is urged by Mr. Darwin as affording 
evidence of an increase of the reef in a period not very remote. 
This is true enough ; but, in connexion with this fact, we 
should remember that marine shells and corals, though much 
weathered and decayed, are still to be found among the trees 
in the interior of certain upraised coral islands in the Solomon 
Group, which were visited and described by the Spanish dis- 
coverers in 1567. 
We possess no reliable evidence to show that a coral atoll 
is rapidly formed. On the other hand, we know that atolls 
have remained in their existing condition for centuries. ‘The 
present Wake’s Island, when it was first discovered to the 
north of the Marshall Islands by the Spaniards in 1567, had 
much the appearance that it presented to Commodore Wilkes 
in 1840. It was described by the Spanish narrator as a low 
uninhabited islet enclosing the sea, and possessing a sandy sur- 
face with some patches of bushes. Commodore Wilkes 
describes it as an uninhabited atoll, probably at times 
washed over by the sea, and bearing shrubs but no trees. 
Again, if we compare the Musquillo Islands of the Marshall 
Group, as described by their Spanish discoverers in 1567, 
with the same islands as described by Captain Bond in 1792, 
we shall observe that the condition of this large double atoll 
did not materially change in the interval. ‘This atoll was 
apparently as thickly populated in 1567 as it is at the present 
day. If, again, as seems very probable, the inhabited Isle of 
Jesus, discovered by the Spaniards in the same year, should 
prove to be one of the northern atolls of the Ellice Group, 
then we have another example of an atoll, which, as pointed 
out by Mr. Woodford, has been occupied by natives of very 
similar habits for over 300 years. Stkyana Atoll, again, as 
we learn from Quiros, was inhabited in 1606 by natives pos- 
sessing the characters of the present occupants. 
The foregoing remarks are for the most part taken from my 
general work on the Solomon Islands, to which reference for 
further details should be made. ‘They are sufficient, I think, to 
show that there are atolls which have been in the same habitable 
state for more than three centuries, and atolls which during the 
same period have remained in a barren, uninhabitable condition. 
The living atoll of the Pacific [am inclined to regard as possess- 
ing great antiquity. Those which, like Mangaia, Tongatabu 
and Savage Island, have been upheaved between 60 and 300 
feet above the sea, are probably of greater age. 
