654 THE POPULAR SCIENCE MONTHLY, 



Search for the sources of bowlders proves that large blocks on the 

 southern flanks of the Jura Mountains must have been derived from 

 Mont Blanc, sixty or eighty miles distant. Instead of passing down 

 the Arne at Chamouni, the blocks proceeded northerly toward the 

 Rhone, and thus across the great valley of Switzerland to the Jura. 

 The magnitude of this ancient action equals much of the wonderful 

 glacial phenomena of other districts in Europe, though hardly equal to 

 what may be seen on this continent. But, being satisfied of the for- 

 mer enormous extension of the Alpine glaciers from examination of the 

 striatums and the diversion of blocks, it is easy to generalize and 

 refer similar phenomena in other countries, whose glaciers are extinct, 

 to the same mighty cause. 



In Scotland there may have been a centre of dispersion for glaciers 

 from Ben Nevis, another in the south part of the province. In Eng- 

 land, one in the Cumberland region; in "Wales, one from Mount Snow- 

 don. It is easy to discover the evidence of radial dispersion. 



A combination of the glacial and iceberg agencies may be dis- 

 cerned in a map in Mr. Geikie's work, showing the courses of the 

 striae marked upon the rocks of Scandinavia. They diverge from the 

 central water-shed between Norway and Sweden — part pushing toward 

 Iceland and Scotland, and part directed toward Lapland and the Bal- 

 tic Sea. The distribution of the bowlders corresponds with these 

 marks. Furthermore, these ice-masses seem to have come in contact 

 with the water of the Baltic, and part have floated over Germany till 

 high land obstructed farther movement, and a part may have been 

 caught by the outflowing Baltic current, carried over the North Sea 

 to the south part of England, and perhaps Iceland. At least, bowl- 

 ders of Scandinavian origin are common in these regions, and have 

 probably migrated in the way described. On the east shore of Scot- 

 land they are plenty ; but, between these and those south of the 

 Thames, none have been found, which fact has given rise to the theory 

 of dispersion by means of icebergs through the Baltic. 



In years past the prominent topic of discussion in scientific associ- 

 ations has been the character of the ice-movements in the Glacier pe- 

 riod. One school has stoutly defended icebergs as the active agent, 

 the other has vigorously insisted upon land glaciation. The example 

 before us seems to require both these agents to account for all the 

 phenomena of this period. Both classes seem to be right, though nei- 

 ther can explain all the facts. Nature's domain is so vast that human 

 intellects do not seem to be capable of grasping the whole truth at 

 once. We are like the mariners who seek to penetrate to the north- 

 pole. They have penetrated a little way beyond Spitsbergen — they 

 have gone nearer the goal through the straits west of Greenland, and 

 have made great exertions in some other quarters. Each party has its 

 theory of the character of the unknown region, as derived from a par- 

 tial survey. By-and-by the whole of this area will be known, and it 



