1874.] Climate of the Glacial Period. 449 
have been much more. A glacial period in one hemisphere 
only would not produce this result, and therefore any 
evidence that tends to prove that the level of the ocean 
was greatly lowered in the glacial period is also evidence 
in favour of the northern and southern ice having been 
contemporaneous. 
Overthe whole world the distribution of manyinsular faunas 
and floras has been explained by the supposition that the 
islands were at one time joined to continents near them and 
to each other, in post-tertiary times. In every case that I 
have examined, the theory is that the last movement of the 
land has been one of depression. ‘Thus the land over which 
the flora of Greenland reached that country from Eurcpe is 
supposed to have sunk down. The lands connecting 
England with Ireland and the Continent, during the forest 
periods before and after the culmination of the glacial 
epoch; the land connecting Malta with Africa; that joining 
the Islands of the Malay ‘Archipelago on one side to Asia, 
on the other to Australia; that connecting the West-Indian 
Islands with Venezuela and Yucatan; and that uniting 
Tasmania with Australia,—are all supposed to have been 
submerged by a sinking of the land, and we have in the 
same areas no corresponding instances of elevation. Whilst 
all islands having shallow channels, however broad, sepa- 
rating them from each other and from not distant continents, 
produce evidence of having been formerly conne¢ted in post- 
tertiary times, on the other hand islands surrounded by deep 
water are distinguished by peculiar faunas. Thus Mada- 
gascar is separated from Africa by a deep sea, and its fauna 
is wonderfully distinét, though it still shows traces of a 
geologically remote connection with that continent. The 
Gallapagos Islands are a still stronger case, for though near 
together they are separated by channels of great depth, and 
Darwin found them tenanted by distin¢t species of reptiles, 
birds, and plants. If the channels were made dry land, by 
- the lowering of the sea, we easily understand why islands 
surrounded by deep water did not lose their insular cha- 
racter ; but on the supposition that they have been produced 
by movements of the land, the reason is not obvious why 
the depressions should have been limited to a certain depth. 
All round the British and Irish coasts, and around 
Western Europe, we have submerged forests passing under 
the bed of the ocean. Some—as that at Cromer—are older, 
others newer, than the greatest development of the ice of 
the glacial period. To allow these forests to have grown, 
we have to suppose an elevation, and for their submergence 
