399 
in high latitudes in and about the polar regions, and to a smaller 
degree also the large snowfields and glaciers in the mountains outside 
these polar regions, must have abstracted large quantities of water 
from the oceans. Owing to this the water in the oceans must in 
the early pleistocene period have sunk relatively to the land. 
After the close of the ice-age i.e. at the end of the pleistocene 
period, the ice-caps in the higher latitudes dwindled down to their 
present state. 
The melting of these ice-caps caused the water to return to the oceans, 
so that the latter have now almost regained the level they had before 
the beginning of the pleistocene period. This implies that, from the end 
of the pleistocene period up to the present day the sea-level along all 
the coasts of tropical regions must have risen relatively to the land. 
Everywhere in the tropical regions the sea must, therefore, have 
encroached upon the land, and where this land rose only slightly 
above the sea-level, the horizontal extent of territory invaded by the 
sea since the close of the pleistocene period must have been considerable. 
_Prnck’) has given us a clear exposition of the influence of the 
pleistocene ice-age (in other ice-ages the same must have taken place) 
on the sea-level as early as 1882. Opinions may differ about the 
degree of oscillation of the sealevel. Observant of some of the 
accessory circumstances which render the problem more intricate, 
calculations have been made by Crom?) in 1875, by Penck in 1882 
and by Dary in 1910 and 1915. Penck in that year arrived at the 
conclusion that in the pleistocene period the sea-level in tropical regions 
must have been 100 m.*®) lower than at present. Afterwards, in 1894 *) 
accepting an average thickness of the ice-caps of 1000 m., be arrived 
at the figure of 150 m., which figure had been mentioned also by 
Von Dryearski in 1887. Daty*), who also assumed that the maximal 
1) A. Penck “Schwankungen des Meerespiegels”. Jahrb. der geogr. Ges. zu 
München VII, 1882, p. 47. In the main PENcK’s statement seems to me undeniable. 
It may be called a theory rather than an hypothesis. 
2) J. Crorr. Climate and time, Londen 1875. 
3) PENCK arrived at this figure (lc. p. 67) on the supposition that in 
the pleistocene age the phenomenon of glaciation was not restricted to one hemisphere 
only, but affected both hemispheres simultaneously, a statement which we endorse 
here. — In case in the pleistocene age the powerful glaciation had been restricted 
to the northern hemisphere only, the position of the general sea-level would, 
according to PENCK, (lc. p. 29) then have been at least 50, and at most 66!/, m. 
lower than at present. 
*) A. Penck. Morphologie der Erdoberfläche Il. p. 660, 1894. 
5) R. A. Daty. Pleistocene glaciations and the coral reef problem. Amer. Journal 
of Science XXX. p. 300, 1910 and The glacial-control theory of coral reefs. Proc. 
of the Amer. Acad. of Arts and Sciences LI, p. 173, 1915, 
