8 
and how the effects of high or low eccentricity of the earth’s orbit 
must have assisted and aggravated those changes, though acting 
over much longer periods than those of the precessional alterna- 
tions every 10,500 years. Assuming this to be the case, which is 
the opinion of most modern geologists, it is evident that we have 
got an approximate standard for the duration of the glacial or 
quaternary period, and therefore for the existence of palolithic 
man, whose remains are found throughout that period, of the 
fauna of which he is a characteristic member as much as the cave 
bear, the mammoth, and the woolly rhinoceros. 
260,000 Years Aco. 
The period of high eccentricity began 260,000 years ago, presum- 
ably towards the end of the pliocene; it rose to a maximum 
210,000 years ago; then declined for 60,000 years; then rose to 
a second maximum lower than the first 100,000 years ago; and 
finally declined and passed into the modern period of small 
eccentricity about 60,000 years ago. These would correspond 
roughly to periods of 200,000 years ago for the first intense 
glaciation which covered Northern Europe with an ice-cap radi- 
ating from Scandinavia; 100,000 for the second great glaciation 
which did not cause an ice-cap, but brought great glaciers down 
from all highlands and mountains ; perhaps 50,000 or 60,000 years. 
for an inter-glacial period between these two maxima ; and 60,000 
or 70,000 for the post-glacial period since the second glaciation 
finally disappeared and the present equable and temperate climate 
was firmly established. 
Tue EvIpENCE OF SUBMERGED Forests. 
It remains to see how far geological facts accord with this 
approximate scale of time. The first stage is the post-glacial, 
during which the physical geography, climate, fauna, and other 
essential conditions have remained substantially the same at pre- 
sent. There has been, however, during this period a number of 
changes in detail, which although inconsiderable compared with 
the great geological changes of former epochs, are in themselves 
of considerable magnitude. Thus the existing river drainage and 
sculpturing of the earth’s surface into hills and valleys by denuda- 
tion, has been done in a great part of Europe during this period. 
Much of the thick deposits which fill the great valleys of the 
north temperate regions must have been accumulated by tranquil 
deposits from the muddy waters caused by the melting of the ice 
and snow of the last glacial period. There certainly was a recent 
time when the German Ocean, and the Atlantic up to the 100 
fathom line was dry land connecting the British Isles, Ireland, 
and all adjacent islands with the Continent of Europe, as is proved 
by the remains of submarine forests, which are found everywhere 
along the western coast from Brittany to Shetland. This forest- 
