es it "Erratic Phenomena about Lake Superior. ‘85 
“The t fesuits “of these ca shane are plainly that the bould- 
' ers found at a distance from the central Alps, sir rele Her their 
- higher summits and valleys, mak were, carried down at different 
successive periods in a regular manner, forming so Ae 
walls and ridges, which can be traced from their starting point to 
-_ their extreme peripheric distribution. 
I have myself shown that there are such — of distribution 
.in Scotland and England and Ireland. Ao 
been since traced in detail in various parts of a British Islands" 
_ by Dr. Buckland, Sir Ch, Lyell, Mr. Darwin, Mr. McLachlan and 
~ Professor 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 . 
lack Forest, and in the Vosges, seg es question, that 
whatever might have been the cause of the ersion of erratic 
boulders, there are — ae seine of hess distributionsto 
be distinguished i in Europe. But there is another question con- 
nected with this local daoeiaigien of boulders which requires par- 
ticular investigation, the confusion of which with the former has 
no doubt greatly contributed to retard our real progress in under- 
standing the general question of the distribution of erratics. 
0 is well known that Northern sn is strewed with bould- 
Their arrangement, however, is such that they cannot be referred 
to one single point of origin, but only in a general way to the 
northern tracts of land which rise above the ‘level of the sea in 
the Arctic regions. Whether these boulders were transported by 
the same agency as those arising from distinct centres, on the 
esent positions, has been the chief objection ms the view that 
To ane the whole question it should be as- 
First, ‘Whe ther the northern erratics were transported at the 
Same time as the local Alpine boulders, and if not, which of the 
