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ices, crept under it, planted iron rods in straight lines 

 across it, and with theodolite and assistant engineers as- 

 certained its motion per hour, the relative motion of its 

 different parts, the effect of that motion upon the rocks 

 and earth adjacent. From these long and laborious inves- 

 tigations in the Alps and the Jura, he extended his re- 

 searches to Britain and afterwards to this continent, com- 

 mencing, as we have seen, on his first short sojourn at 

 Nova Scotia, and continuing it wherever he went: His 

 theory was that the earth from each pole to about the 

 latitude of 32 degrees north and south of the equator was 

 once enveloped in great sheets of ice thousands of feet 

 thick, which gradually retired as climates were established, 

 receding pole-ward and remaining yet in Greenland, 

 whence the icebergs come. Agassiz was always hunting 

 for evidences of g!acial action, and always finding it, un- 

 til his theory has become in great part established, though 

 some of its details even yet remain among the agenda of 

 science — things yet to be proven. The never tiring dili- 

 gence of Agassiz and the keen insight exhibited in his ob- 

 servations of glacial action, led some one to say that every 

 boulder would hereafter be his monument. The immense 

 rocks often found in this country, frequently on the level 

 prairie, with generally deep furrows cut upon their sur- 

 faces, were as much a puzzle to most people before the 

 glacial theory as were the marine shells found on moun- 

 tain tops before Leonardo da Vinci's fossil theory ex- 

 plained them. It was as reasonable, too, to suppose they 

 grew by some occult force in nature where they are 

 found, as was contended by wise men in the case of marine 

 fossils found many thousands of feet above the level of 

 the sea. Granite boulders in great numbers are found 

 hundreds of miles south of any granite stratum, which in 

 this region does not show itself south of Lake Superior. 

 They often weigh many tons, are found on or near the 

 surface, and distant from rock of any kind. It is'clear 

 they must have grown there, or have been carried in gla- 

 ciers or icebergs, which are floating fragments of glaciers. 

 Wordsworth refers to these boulders, once regarded with 



