254 The American Geologist. October, 1902. 
ces, while its capacity for work, which brings in the time ele- 
ment prominently, is indicated by the vast amount of debris of 
finer material that has been removed from one locality and de- 
posited in another as morainic formations. Some idea concern- 
ing- the laiter factor will at once be gained by remembering the 
amount of material transported by some of the former glaciers 
in the Alpine lands, elsewhere considered, though continental 
glacier moraines are subsequently discussed. Concerning the 
movement of erratics Geikie says. "It is a fact that most, if not 
all. the erratics have traveled in directions that coincided with 
the trend of the rock striae." They are of all shapes and sizes 
and are found resting alike upon bare rock, ang-ular debris, and 
morainic hills, having as a general rule been carried from higii- 
er to lower levels, though exceptions to the latter are sometimes 
found, the erratic being at a higher level than the parent rock 
formation. For example. Home found granite erratics at a 
hight of 2,764 feet, while the highest level of the granite in 
place was only 2,270 feet.* 
These exceptions which are found both in Europe and 
America have been for glacialists a more or less puzzling prob- 
lem to solve. Darwin, years ago, attempted an explanation on 
the supposition that these erratics were borne about by ice- 
bergs, which as the land sank down, dropped their burdens on 
higher and higher prominences of the drowning country. This 
l^elief became untenable soon after it was expounded, and the 
idea of deposition by land ice gained precedence first by .Scan- 
<linavian geologists, and later by Forbes, Geikie, and others. 
Geikie says of a glacier transporting rocks imbedded in the ice 
mass, "A great deal will depend upon the boldness of the ob- 
structions that impede tlie flow of the glacier. If these are 
numerous and fomiidable, then the lines O'f ejection will ap- 
proximate more and more to the horizontal, and even at last 
•curve upward, so as to dip up instead of doivn the valley ; and 
thus boulders introduced into the ice at a given point will, as 
they are borne down the valley, not only rise, as it were, 
through the glacier, but eventuall\" be extruded at a level which 
may be many feet, or even many yards, higher than the point 
in the valley from which they originally started." 
This explanation is a most plausible one, for if we consider 
the enormous depth of the ice in some portions of the ice sheet, 
•Geikie. Great Ice Ase, 1S94. 
