§4 The Loess of the Rhine and the Danube . [January, 
covered with water over which icebergs floated, carrying 
the erratic blocks. 
During a visit I made to North America, in 1874, I found 
many more proofs that the drainage of the north-eastern 
part of that continent was blocked up by ice that flowed 
down the bed of the Atlantic from the direction of Green= 
land, and I learnt from Prof. James Hall that Cape Cod was 
a huge terminal moraine. Knowing, also, that on the 
European side of the Atlantic Mr. Robert Chambers had 
been led to the conclusion that Scotland had been glaciated 
from the north-west, that Mr. Thos. Jamieson had shown 
that Caithness had been overflown from the same direction, 
and that there was much other evidence pointing to the 
same conclusion,* I was led to believe that the drainage of 
Europe had been blocked up— not by Scandinavian ice, but 
by that which occupied the bed of the Atlantic and had 
reached to our western shores. 
If we try to picture in imagination what would happen if 
the Glacial period were to return again, the continents 
keeping their present form, we shall not find it so improbable 
as it seems at first sight that the ice should advance down 
the ocean beds and be thicker there than on the land. The 
first effedt would probably be a great increase of the ice on 
areas such as Scandinavia and the Alps, where it exists at 
present, but especially on Greenland, which lies at the 
northern end of the great evaporating basin of the Atlantic. 
For the ice would accumulate fastest where the frozen pre- 
cipitation was greatest, and without great evaporation there 
could not be great precipitation. We need not carry on in 
imagination what happened in Scandinavia and the Alps, 
for we know what did occur, and can trace the great ex- 
tension of the ice by the marks it has left on the rocks it 
passed over. We need only, for the present, try to follow 
the progress of the far greater accumulation of ice that was 
taking place in Greenland. When it there reached to such 
a height that it intercepted all the moisture of the currents 
of air travelling over it northwards, the precipitation would 
be confined to its northern slope, just as the Atlantic slopes 
of Central America drain the north-east trades of their 
moisture, so that they are dry winds on the Pacific side. 
But as the precipitation would not, as in Central America, 
run down immediately to the sea, but be retained on the 
southern slope of the frozen mass in the shape of snow and 
* See Quart. Journ. Geol, Soc., voL xxxii., p. 85, where a portion of the 
evidence I laid before the Society has been published. 
