304 Hicks on the (R.eef=-(B2dlders. 
his reasoning in locating the Hne A A ("the axial line of this 
great Pacific subsidence") upon the Physiographic Chart at the 
end of his Manual of Geology. Murray maintains that atolls 
are no more to be taken as evidence of a sinking bottom than 
other coral formations. They begin upon submarine banks 
within 120 feet of the surface and assume the circular form 
simply by reason of the vigorous growth at the periphery, and 
the dwindling or death of the polyps nearer the center. Even 
Darwin admits this explanation as a possibility. The founda- 
tion for the atoll may be a hidden rock or the accumulations of 
pelagic life upon the higher parts of the sea floor, raising them 
within reach of the reef-builders. 
Prof. Semper has long maintained that the atolls of the Pelew 
group not only fail to prove subsidence, but that the facts are 
all against Darwin's interpretation. Instead assuming sub- 
sidence as a necessity he claims that "the problem ought in each 
case to be determined by actual detailed observation." That 
a given reef region may have subsided, and that the reefs do in 
that case owe their form largely to the fact of subsidence, he is 
quite ready to admit, and so are all the anti-Darwinians. But 
they insist that subsidence is not a necessary condition of the 
problem, and hence that atolls do not simply by virtue of their 
pi'esence prove a downward movement of the region in which 
they occur. If such a movement has occurred then the atoll 
may very well be the last term of a progressing series, as Dar- 
win supposed, but the whole series cannot be inferred from the 
existence of the atoll. 
Darwin should not be held responsible for the views of his 
followers, unless they were his own. It would be a delicate 
and thankless task, however, to attempt to draw the line be- 
tween his real opinions and the exaggerations of his followers. 
Without attempting any such distribution of praise or blame I 
am constrained to remark that the impressions produced upon 
the reader by most of the current geological literature are mis- 
leading, and the discussion now in progress was needed in order 
to clear our vision. For an example I will refer the reader to 
an excellent book, Prestwich's Geology,^ recently published. 
^ Geology, Chemical, Physical and Stratigraphical. By Joseph Prest- 
wich, Oxford, 1886. 
