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atolls. As a matter of fact within the geographical limits of the 
reef-building corals exactly these islands are almost without exception 
surrounded by barrier-reefs and the great majority of the atolls 
occur exactly in the same areas where both voleanic islands and 
barrier-reefs are found. 
In appears to me that the yielding and slow sinking of the volcanic 
islands under the influence of gravity?) must be regarded as the 
cause of the downward movement of large amount and long duration 
which mnst be assumed in order to explain the formation of barrier- 
reefs and atolls in true oceanic regions, the cause of which had as 
yet not been ascertained. 
By accepting this hypothesis which restricts the subsidence to the 
islands themselves and their direct basements *) and does not postulate 
large crustal movements nor great displacements of masses, one can 
meet the most serious of the objections, raised against the theory 
of Darwin-Dana, even by its adherers, which were mentioned in 
the beginning of this paper. 
It is clear that the rate of sinking of all voleanie oceanic islands 
will always depend on the local composition of the island and of 
the sima of the underground and that moreover by various influences 
this movement can be counteracted either really or apparently. 
Thus the subsidence can temporarily be counteracted in reality 
by diastrophism and also by variations of the sea-level, as e.g. by 
the general lowering of the sea-level in early pleistocene times, 
to which Prxck and later especially Dary in his “glacial control 
theory” have drawn attention; apparently it can be counteracted 
by prolonged volcanic activity, by which such islands might gain 
') The effects of crustal warping of the ocean floor caused by diastrophism e.g. 
by folds, will have just as little chance to remain in existence. After having been 
formed the elevated portions will yield and sink away again by the influence 
of gravity, although in all probability very slowly. 
*) G. GERLAND in his very important paper cited above also assumes that not 
the floor of the Pacific itself has subsided. He wants to restrict this downward 
movement to the tops of the voleanoes which, as he thinks, may move upwards 
as well as downwards under volcanic influence. Compare |]. c. p. 56: “Senkung 
und Hebung der Koralleninseln sind Erscheinungen gleicher Art und zwar beide 
Erscheinungen, welche dem Vulkanismus der Erde angehören”. (Sinking and rising 
of the coral islands are phenomena of the same order, both of them belonging 
to terrestrial volcanism). He does not try to explain the cause of the subsidence 
of the voleanic cones, although he takes subsidence to be well proved. He remarks 
on this point Lc. p. 66: “Das Sinken zu erklären vermag ich nicht; man gestatte 
mir nur, auf einzelne hierhergehörige und, wie mir scheint, sichere Thatsachen 
hinzuweisen”. (The subsidence I cannot explain; | only beg to draw attention to 
facts pointing to it which I regard as well established). 
