1874.] Climate of the Glacial Period. 453 
Mr. A. G. Renshaw has pointed out to me that the melting 
of the ice of the Glacial period must have occupied thousands 
of years, and I am quite convinced that it must have done so. 
The gradual growthof coral islands, and the silting up of deltas 
filled with fresh-water deposits, cannot be explained if we 
adopt the hypothesis that the ice was suddenly melted. But 
we do not require thousands or even hundreds of feet of sub- 
mergence to overwhelm low-lying tra¢ts of country, and I 
think we may fairly assume that there would be some sudden 
rise of the sea-level, scores of feet at least, through the rapid 
melting of great quantities of ice, as, for instance, when the 
warm ocean currents from the south first gained access to 
the Arctic regions, or when the immense fresh-water lakes of 
northern Europe and Asia, pounded back by the ice, broke 
through their melting barriers and ran down to the ocean. 
Marine deposits found alternating with land surfaces in the 
deltas of the Mississippi and the Po indicate such occasional 
more rapid advances of the sea. It may be said that I am 
advancing one theory—that of the lowering of the sea-level 
during the Glacial period—to strengthen another—that of 
the production of the Glacial period by an increase of the 
obliquity of the ecliptic ; but the lowering of the sea is more 
than theoretical,—it is a necessary consequence of the heaping 
up of ice around both poles at once, and any evidence that 
it was greatly lowered in Glacial times is also evidence in 
favour of the theory of the increase of the obliquity of the 
ecliptic, which would produce a Glacial period in the two 
hemispheres at the same time. 
Whilst we have thus many indications of a general rise of 
the sea-level since the culmination of the Glacial period, we 
have a remarkable eseeE HOR in arise of land towards the 
north and south poles, which is believed to be still in 
progress. In the southern hemisphere it is certainly still in 
operation at intervals in the southern extremity of South 
America and in New Zealand. In the northern hemisphere 
it has been better observed on account of the greater amount 
of land around the polar regions. One line of elevation 
commences in Scandinavia at Stockholm on the eastern, and 
near Gothenburg on the western, coast, increasing north- 
wards as far as the North Cape, where there are marine 
_ post-glacial deposits 600 feet above the sea. The land has 
been elevated since the Glacial period, for the raised beaches 
everywhere rest on the boulder clay with transported blocks. 
Professor Kjerulf, of Christiania, has shown that the highest 
sea-terraces contain Arctic shells, which indicate that the 
VOL. IV. (N.S.) 3M 
