88. Erratic Phenomena about Lake Superior. | 
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sre’ of latitude, before it had reached the great barrier off ‘hie 
: ask whether there was such a barrier in the unlimitéd ’- 
plains which stretch from the Arctic seas uninterrupted over thes — 
whole northern continent of America as far down as the Gulf of — 
sk, again, why the erratics are circumscribed within the 
Ia : 
northern limits of the temperate se if their transportation is. ~ 
‘,owing to the action of water currents? Does not, on the con- 
trary, this fhost surprising limit within the arctic and northern 
temperate zones, and in the same manner within the antarctic. 
and southern temperate zones, distinctly show that the cause of 
transportation is connected with the temperature .or climate ofe 
.. the countries over which the phenomena were produced. If it 
~~ were otherwise, why are there no systems of erratics with an 
east and west bearing, or in the main direction of the most ex- 
sow peenseote flowing at present over the surface of our globe? 
matter of fact, of undeniable fact, for which the theory 
has i debut that in the two hemispheres the erratics have di- 
rect reference to the polar regions, and are circumscribed within 
This: fact 
the arctics and the colder part of the temperate zone. is: 
is as plain as the other fact, that the local distribution of boulders 
has reference to high mountain ranges, to groups of land raised 
above the level of the sea into heights, the temperature of which 
is lower than the Rn plains. And what is still more as- 
tonishing, the extent of the local boulders, from their centre of 
distribution reaches levels, the mean annual temperature of which 
corresponds in a surprising manner with the mean annual temper- 
ature of the southern limit of the northern erraties. 
We have, therefore, in this agreement a strong evidence in fa- 
vor of the view that both the phenomena of local mountain er- 
ratics in Europe and of northern erratics in — and America 
have probably been produced by the same 
The chief difficulty is in conceiving the possibility of the 
formation of a sheet of ice sufficiently large to carry the northern 
erratics into their present limits of distribution ; but this difficulty 
is greatly removed when we can trace, as in ‘the Alps, the pro- 
gress of the boulders under the same aspect from the glaciers 
now existing, down into regions where they no longer exist, but 
where the boulders and other phetiomena os their trans- 
portation show distinetly that they once ex 
Without extending further this Meet eos I would call the 
attention of the unprejudiced observer to the fact, that those who 
advocate currents as the cause of the transportation of erratics, 
have, up to this day, failed to show, ina siugle instance, that cur- 
rents can produce all the different t phenomena connected with the 
