16 J. H. MAIDEN. 
Mauna Loa. At about one hundred and forty fathoms from the 
surface, an abrupt change in the declivity of the slope occurs, for 
at this point a wall-like rampart rises on all sides of the atoll. 
Tt is difficult,” says Prof. Sollas, ‘‘ to resist the impression that 
it is the upper one hundred and forty fathoms which represents 
the true coral reef.” It will of course be obvious to you that 
Prof. Sollas’ interpretation of the contour of Funafuti as a volcanic 
cone crowned with a coral cap some eight hundred feet thick (less 
if the reef advanced on a coral talus), calls for no great amount of 
subsidence. 
During the stay of the boring party the fauna, flora, and 
ethnology of Funafuti were studied by Mr. Hedley, who accom- 
panied Prof. Sollas as naturalist. Mr. Hedley made excellent 
use of his time, and the results of his personal observations, and. 
of his own work and that of other specialists on his collections, 
form the subjects of several parts of a memoir which have already - 
been issued by the Australian Museum. 
Though unfruitful in the principal object, the voyage of the 
“Penguin” has advanced the study of the subject along other 
lines. Her surveys have suggested to Admiral Wharton an 
original and brilliant hypothesis on the origin of atolls! The 
fact that all atolls stood on the same level was advanced by 
Darwin as a convincing proof of his theory of subsidence. A 
satisfactory explanation of the uniformity of level without invok- 
ing subsidence is offered by the Hydrographer, who points out 
that submarine volcanoes void chiefly ash and such loose matter, 
that at the close of an eruption such a pile is first denuded by 
aerial agencies to the sea level, and then by marine forces to 
whatever depth wave action extends. Proofs are advanced to 
show that submarine erosion cuts deeper than is generally sup- 
posed. The flat top of the volcanic peak thus ground down he 
considers as the lagoon floor of the future atoll around whose 
rim the coral ring grows up. 
1 Nature, Feb. 25, 1897. 
