454 ; RECENT ADVANCES IN GEOLOGY. 
must not hereafter be disregarded in treating of the past 
and present condition of' humanity. We must weigh the 
value of observations and press them to legitimate conclu- 
sions. The investigator at this day is not to be tram- 
melled, in the language of Humboldt, by “an assemblage of 
dogmas bequeathed from one age to another"—by "a physi- 
cal philosophy made up of popular prejudices.” 
The periods of the prehistoric man have been divided by 
M. Lartet, into two ages :— 
1. The Stone Age, and (2) the Metal Age. 
The Stone Age has been subdivided into three epochs. 
1. That of the extinct animals, such as the mammoth and 
cave-bear. | 
2. That of the migrated existing animals (Reindeer 
Epoch) 
3. That of the domesticated existing animals (Polished 
Stone Epoch). 
The Metal Age has been divided into two epochs: 
1. That of Bronze, and (2) that of Iron. - 
The elder man differed widely from the intellectual and 
much-planning man of this day. The conditions of climate 
greatly modified his modes of thought and physical pursuits. 
The northern hemisphere was just emerging from a long- 
continued state of glaciation. The snows which had 
wrapped the earth as in a mantle, were melting, and the 
great glaciers were reluctantly retreating within the Arctic 
Circle. Every depression became a lake, and every lake a 
sea for the reception of the accumulating waters, whose re- 
sistless foree swept along mud, and sind, and shingle, and 
fragments of rocks. As "the barriers gave way, the waters 
cut out channels on their route to the sea, and the terraces 
and ridges which border our lakes and rivers are but the 
monuments of their erosive action. It was a sad and deso- 
late land, to be paralleled only in the Arctic Circle. But 
man was not alone. On the European Continent there was 
a strange assemblage of: animals; the elephant, with his 
