312 J. Croll— Arctic Interglacial Periods. 
Lee periods. A more special and thorough search of those 
eds might probably reveal further indications of interglacial 
age. 
Was Greenland free from Ice during any of the Interglacial 
Periods ?—There is nothing whatever improbable in the sup- 
position that during some of the earlier interglacial periods, 
when the eccentricity was about a maximum, the ice might 
have completely disappeared from Greenland, and the country 
become covered with vegetation. 
Mr. Wallace thinks that the existence at present of an ice- 
sheet on Greenland is to be explained only by the fact that cold 
currents from the polar area flow down both sides of that contl- 
nent. He further thinks that could these two Arctic currents 
be diverted from Greenland, “that country would become free 
a and might even be completely forest-clad and habit- 
able.” 
sions, simply because there happens to be about two inches 
more of ice annually formed than is actually melted. It cet 
tainly would not require any very great change in the resent 
physical and climatic conditions of things to melt two additional 
inches per annum. If this were done the ice would ultimately 
disappear. A simple decrease in the volume of the two 
currents might possibly bring about such a result, A cause 
more effectual would, however, be an increase in the temper@ 
ture and volume of the Arctic branch of the Gulf-stream. 
Note.—This will probably be my last paper on pee 
relating to geological climate. There are many points should 
have wished to consider more fully, but advancing years and 
declining health have rendered it necessary for me to abandon 
the subject altogether in order to be able to finish some work, 
in a wholly different field of inquiry, which has been laid aside 
for upwards of a quarter of a century. 
* ‘Island Life,’ p. 149. 
