1883.] Geological Effects of a Varying Rotation of the Earth. 23 
same regions, in the age preceding the depression just mentioned, 
and to an altitude far exceeding the present. As to relations of 
these periods to the prevalence of glaciers, there is not so com- 
plete harmony among geologists, but that need not affect our 
theory. Moreover this vast vibration seems to have had greater 
amplitude, in general, in proportion to nearness to the poles. 
This is well shown in the discussion of the matter by Professor 
Dana, in his Manual of Geology, pp. 552-558. 
For the tropical regions in the same periods we cannot say as 
much, Comparatively few observations are reported which have 
any decisive bearing on their movements. It will be readily seen 
that we should expect a general elevation immediately preceding 
the present epoch. 
Wallace, from his profound studies of the fauna and flora of 
Java, Sumatra and Borneo, concludes that they were submerged 
during the Miocene, but “at some later period a gradual eleva- 
tion occurred, which ultimately united them with the continent. 
This may have continued till the glacial period in the northern 
hemisphere, during the severest part of which a few Himalayan 
species of birds and mammals may have been driven southward. 
Java was first separated by subsidence, then a little later Sumatra 
and Borneo.”! He, from similar data, judges Celebes to be a 
fragment of the great eastern continent in perhaps Miocene 
times. This suffices to show a vibration in tropical areas, such as 
our theory demands, except that its time is not definitely deter- 
mined. It seems not improbable that they may have been ele- 
vated through the Pliocene, been depressed during the Glacial 
epoch, then partially elevated during the Champlain, and again 
depressed, perhaps to a greater extent, which movement continues 
to the present, except where counteracted by volcanic influences. 
From New Guinea and Australia we find nothing recorded 
which will throw any light on their movements, in the epoch 
preceding the present. Nor can we hope, perhaps, to find any- 
thing in the coral islands bearing on this stage of our case. It is 
barely possible that some of them which are much elevated, as 
Elizabeth island, Metia, Rurutu and others (vide Dana’s Coral 
islands), may ultimately prove to be monuments of such an eleva- 
tion as well as of a still earlier depression, deeper than that of the 
present. And if it be incredulously asked, What, then, has be- 
1 Island Life, p. 353. 
