70 
Discovery of Stone Implements in 
[January, 
that is now covered with a shallow sea then formed wide 
pasture-grounds for the great pachyderms and their asso- 
ciates. Palaeolithic man likely lived on higher and drier 
land, and found a plentiful subsistence amongst the deer and 
the wild horses and oxen that appear to have abounded. 
Probably this state of things was of long duration, but 
at last there came a catastrophe; possibly the greatest that 
has befallen the human race, yet of immense benefit in its 
ultimate results. The ridge of ica in the Atlantic had been 
slowly advancing, and through time it coalesced with that 
from the Cantabrian Range, whilst at the same time the 
gap between the Pyrenees and the Maritime Alps was also 
closed with ice. I suppose that the communication of the 
Black Sea with the Mediterranean had not then been 
effected, and that the ice of the Pacific blocked up the out- 
let of the waters to Behring’s Straits. An immense basin 
was thus formed, the drainage of which to the sea was in- 
tercepted. The consequence would he that the low lands 
would be soon submerged. The pent-up waters ultimately 
reached a height of about 1700 feet above the sea, as evi- 
denced by the great outspread of gravels at Munich, Bern, 
and Geneva ; but whether this extreme height belonged to 
the first or second rise I do not yet know. To this great 
flood I ascribe the formation of the lower boulder clays and 
diluvium, and the destruction of the great mammals that 
were caught on the low plains and have left there their 
bones in great abundance. The first great European lake 
was apparently not of long duration, but was suddenly and 
tumultuously lowered by the breaking away of the ice-dam ; 
probably, I now think, between the Pyrenees and the Mari- 
time Alps. The rushing flood or debacle swept off from the 
flanks of the hills much of the detritus that covered them, 
and mingled all together in the great sheets of gravel that 
are now spread over much of the low country. Thus were 
formed, I think, the middle sands and gravels (including 
the Thames and other valley gravels), in which have been 
caught up or which cover the bones of the pre-diluvial 
mammals or the stone implements of pre-diluvial man. As 
no land surface has yet been detected between the middle 
sands and gravels and the upper boulder clay, it is probable 
that the break in the rim of the lake basin was soon filled 
with ice again, and the great lake re-formed. Over it 
floated icebergs from the north, carrying great boulders from 
the mountains of Scandinavia and scattering them over the 
German plain and as far as the flanks of the Carpathians. 
At this time was formed the upper boulder clay and diluvium 
