GEOGRAPHICAL DISTRIBUTION 179 



south. As the tide leaves its drift in horizontal lines, 

 rising higher on the shores where the tide rises highest, 

 so have the living waters left their living drift on our 

 mountain summits, in a line gently rising from the Arctic 

 lowlands to a great altitude under the equator. The 

 various beings thus left stranded may be compared with 

 savage races of man, driven up and surviving in the 

 mountain fastnesses of almost every land, which serves 

 as a record, full of interest to us, of the former inhabi- 

 tants of the surrounding lowlands. 



