1877J The Loess of the Rhine and the Danube. 87 
self-sustenance and growth that might cause it to spread 
like a living organism. 
The height of the ridge of ice and snow would increase 
as it advanced southward, for it would depend upon that to 
which the moisture would be raised before it was precipi- 
tated, and this would be greater in low latitudes than 
in high. 
I believe it is essential in any explanation of the fadts of 
the Glacial period to bear in mind that from its commence- 
ment to its culmination the zone of frozen precipitation was 
gradually advanced southward in the northern hemisphere. 
On the Continent of Europe it was moved from Scandinavia 
and the Swiss Alps to the Pyrenees and the Maritime Alps, 
and when the ice was highest on the latter ranges that on 
the former must have shrunk back on account of the pre- 
cipitation being intercepted further south, just as there are 
no glaciers now on the Altai Mountains because the mois- 
ture is intercepted by the Himalayas. As the ice gathered 
on the Maritime Alps, the Pyrenees, and probably on the 
Cantabian Range, the glacial ridge of the Atlantic was 
gradually advancing southward, and at last I suppose it 
coalesced with the ice of the Pyrenees or of the Cantabian 
Range. I thought, up to a recent period, that the Atlantic 
ice might have reached the coast of Europe near Brest, and 
so blocked up the drainage of the northern part of the con- 
tinent, but I obtained proof during a visit to the valley of 
the Rhone this year, that it also was included within the 
area of the Great European Lake. This would be effected 
by the ice of the Atlantic glacier and that of the Pyrenees 
or of the Cantabian Range meeting on one side, and that of 
Pyrenees and of the western prolongation of the Maritime Alps 
on the other. Or the ice on the Cevennes may have met that 
of the western Maritime Alps and that of the Pyrenees ; or 
the ice of the Atlantic glacier may have flowed across the low 
stretch of country north of the Pyrenees. How, precisely, this 
gap was blocked up I do not yet know, as I have not been able 
to examine it for myself, and I have had to work out the whole 
problem of the advance of the Atlantic ice and its inter- 
ception of the European drainage, alone and unaided. 
The Atlantic ice has left traces of its progress on 
every island and coast of the western side of Scotland 
and Ireland. The glaciers of the Pyrenees have been 
traced down unto the low plains to the north of that 
range,* and with regard to those of the Maritime Alps Mr. 
* C. Martins, Revue de deux Mondes, 1867, 
