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me i * Erratic Phenomena about Lake Superior. a) 
eS following the cracks in the rocks, or hollowing their softer parts ; 
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‘but continuous straight lines, especially such crushed lines and 
straight furrows, | have never seen. is 
en we know how extensive the action of water carrying © 
mud and gravel is on every shore and in every water current,— 
when we can trace this action almost everywhere, and no where 
find it similar to the phenomena just described, I cannot imagine 
upon what ground these phenomena are still attributed to thes 
agency of currents. This is the less rational as we have at pres- 
ent, in all high mountain chains of the temperate zone, other 
agents, the glaciers, producing these very same phenomena, with 
.precisely the same characters, to which, therefore, a sound phi- 
losophy should ascribe, at least conditionally, the northern and 
Alpine polished surfaces, and scratched and groowed rocks, or at 
least acknowledge that the effect produced by the action of gla- 
ciers more nearly resembles these erratic phenomena than does 
that which results from the action of currents. But such is the 
prejudice of many geologists, that. those keen faculties of distinc- 
tion and generalization, that power of superior perception and 
discrimination which have led them to make such brilliant dis- 
coveries in geology in general, seem to abandon them at once as 
soon as they look at the erratics. The objection made by a ven- 
erable geologist, that the cold required to form and preserve such 
glaciers, for any length of time, would freeze him to death, is as 
childish as the apprehension that the heavy ocean currents, the 
action of which he sees everywhere, might have swept him 
ay. : 
Now that these phenomena have been observed extensively, 
We may derive also some instruction from the limits of their geo- 
graphical extent. Let us see, therefore, where these polished, 
Scratched and furrowed rocks have been observed. biel 
In the first place they occur everywhere in the north within 
certain limits of the arctics, and through the colder parts of the 
temperate zone. They occur also in the southern hemisphere, 
within parallel limits, but in the plains of the tropics, and even in 
he warmer parts of the temperate zone we find no trace of these 
Feofomens, and nevertheless the action of currents could not be 
ess there, and could not at any time have been less than in the 
colder climates. It is true, similar phenomena occur in Central 
Europe and have been noticed in Central Asia, and even in the 
Andes of South America, but these always in higher regions, at 
definite levels above the surface of the sea, every where indicating 
@ connection between their extent and the colder temperature of 
the places over which they are traced. 
* Berlin Academy, 1846. 
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