88 The Loess of the Rhine and the Danube . [January, 
Moggridge states that he has found abundant proofs that 
they descended to the level of the present Mediterranean, 
near Mentone.* 
If, at the time the Atlantic ice and that of the southern 
ranges I have mentioned blocked up the drainage of Europe, 
the upper end of the Northern Pacific was also filled with 
ice, or only so far as the mountains of Kamtchatska, a 
great continental basin of water would be formed, rimmed 
in on its southern side by the ranges of mountains that 
extend from the extreme north-east of Asia to the Alps. 
The only break now existing in that rim is through the Bos- 
phorus, and both physical geographers and naturalists have 
come to the conclusion, on independent grounds, that the 
Black Sea did not communicate with the Mediterranean 
until after the close of the Tertiary period, and the excava- 
tion of the channel that connects them must have been 
effected about the time of the Glacial period. Probably it 
was made when the whole drainage of northern Europe and 
Asia was intercepted and turned in that direction. That the 
waters of the Great Lake flowed that way is indicated by the 
Scandinavian drift having been carried far over the plains of 
Russia, and by the vast extent of diluvial clay spread out 
around the north-western shores of the Black Sea. 
In this way I consider the waters were raised, over which 
floated icebergs from the north carrying the Scandinavian 
drift, and into this great lake the Danube and the Rhine, or 
the upper portions of them above its level, brought down 
fine mud from the glacier-capped Alps, which was deposited 
as loess. The waters everywhere were muddy, for glaciers 
were still triturating the mountains of Scandinavia, and 
thus the fine clay was spread over Europe as far as the lake 
extended. The very fadf that the glacial waters carried fine 
mud in suspension to such great distances is another proof 
that they were fresh, for it has been abundantly proved by 
Dr. Sterry Huntt and^others that in salt water mud is quickly 
precipitated, whilst in fresh it remains a long time in sus- 
pension. 
I think there is evidence that the lake reached a height of 
1700 feet above the sea, and that it remained for a long time 
at about 1200 feet. It was once completely drained ; at 
first gradually, but from about 500 feet above the present 
level of the sea suddenly and tumultuously by the breaking 
away of the icy barrier, and thus was produced a great 
deluge or debacle that swept over the lower lands and 
* Proc. Geol. Soc., London, 1876, p. 127. 
f Proc. Boston Soc. Nat. Hist., February, 1874. 
