396 LAKE SUPERIOR. 



out Speaking of my own and some contributions from visitors, as 

 the Martins, James Forbes and others, to justify my assertion that 

 no important fact respecting the loose materials spread all over 

 Switzerland has been added by the advocates of currents since the 

 days of Saussure, DeLuc, Escher and Von Buch ; whilst Prof, 

 Guyot has most conclusively shown that the different erratic basins 

 in Switzerland are not only distinct from each other, as was already 

 known before, but that in each the loose materials are arranged 

 in well-determined regvdar order, showing precise relations to the 

 centres of distribution, from which these materials originated ; an 

 arrangement which agrees in every particular with the arrangement 

 of loose fragments upon the surface of any glacier, but which no 

 cause acting convulsively could have produced.* 



The results of these investigations are plainly that the boulders 

 found at a distance from the central Alps, originated from their 

 higher summits and valleys, and were carried down at different suc- 

 cessive periods in a regular manner, forming uninterrupted walls and 

 ridges, which can be traced from their starting point to their 

 extreme peripheric distribution. 



I have myself shown that there are such centres of distribution in 

 Scotland and England and Ireland. And these facts have been 

 since traced in detail in various parts of the British Islands by Dr. 

 Buckland, Sir Ch. Lyell, Mr. Darwin, Mr. McLachlan and Profes- 

 sor James D. Forbes, pointing clearly to the main mountain groups 

 as to so many distinct centres of dispersion of these loose materials. 



Similar phenomena have been shown in the Pyrenees, in the 

 Black Forest, and in the Vosges, showing beyond question, that 

 whatever might have been the cause of the dispersion of erratic 

 boulders, there are several separate centres of their distribution to 

 be distinguished in Europe. But there is another question connect- 

 ed with this local distribution of boulders which requires particular 

 investigation, the confusion of which with the former has no doubt 



*A comparison of the maps showng the arrangement of the moraines upon the 

 glacier of the Aar in my Syst^mc Glaciaire, with the map which Prof. Guyot is about to 

 publish of the distribution of the erratic boulders in Switzerland, will show more fully 

 the identity of the two phenomena. 



