Reviews—Dr. H. B. Guppy’s Geology of Solomon Islands. 171 
as little more than a facing or veneer upon the really bulky ooze 
deposits. Such an arrangement tallies far better with the develop- 
ments of reef-building coral known to exist in our own islands than 
the more stupendous thicknesses assigned to reef rock under the 
subsidence hypothesis. Indeed the author claims that these excessive 
thicknesses may be altogether hypothetical in the majority of cases. 
It has, we believe, been no uncommon thing for geologists to over- 
estimate the thickness of beds from various causes. As a familiar 
instance of this, we may cite the classical section of Assynt, where, 
according to the interpretation of Sir R. Murchison, a thickness of 
thousands of feet was assigned to the quartzite-limestone series of 
Ben More; whereas, if that celebrated geologist had taken the 
trouble to penetrate into the heart of the mountain, instead of 
inspecting its flanks alone, he would have found that this imposing 
and seemingly solid array was merely a casing over the great 
Archean masses beneath—a trap, in fact, set by nature to catch 
those who are in the habit of taking a one-sided view of things. 
Naval men of experience are evidently beginning to doubt the 
sufficiency of the subsidence theory to explain the production of 
barrier reefs and atolls. This has been made very plain by the 
notice on Coral Formations from the Hydrographer to the 
Admiralty which appeared in “ Nature” (Feb. 25, 1888). At the 
same time we must guard ourselves against any unfair imputations 
which it may be sought to fasten upon the principal author of the 
subsidence theory, in view of its possible collapse. 
That most judicial of all writers took into consideration the 
majority of the theories which had been advanced in his day, and if 
he ultimately decided in favour of the subsidence theory, it was more 
from lack of evidence than from any other cause. But the master 
is generally surpassed by the disciple in the implicitness of his 
faith. The latter, fascinated by an explanation which, in this case, 
has the merit of great ingenuity, and possessed by a natural un- 
willingness to admit that his wisdom is foolishness, views with 
suspicion anything likely to compromise his orthodoxy. 
Such considerations may possibly help to account for the nervous 
reluctance of many geologists to accept any explanation of the origin 
of coral reefs unconnected with or adverse to the subsidence theory. 
It is perfectly true that Darwin had Dr. Murray’s facts and inferences 
before him, and that he made no sign of change in his views (letter 
dated 1880, quoted by Mr. Mellard Reade in ‘“ Nature,” Nov. 17, 
1887), nor have we any absolute right to assume that even the 
remarkable physical history of the Solomon Islands would have 
induced him to modify them. But no matter how great may be the 
authority of any one individual, living or dead, if a series of facts, 
such as those recorded in the work before us, are plainly repugnant 
to the theory of subsidence in connection with the growth of reef- 
coral, it is the manifest duty of geologists especially to examine 
such facts without prejudice, and to be ready to modify their views 
in accordance with the ever-advancing tide of scientific knowledge. 
Wis Eee 
