No. 386.] . THE PENEPLAIN. 129 
can conceive many geological processes or not does not alter 
the facts of geology. The velocities of the planets are real, 
though never adequately conceived by the astronomer. The 
work has been done — “ How?” is the question. To reason 
truly and effectively about the genesis of a land-form, we must 
put away from our minds any proneness to measure the scale 
of the operations by reference to the standards of a human 
life. It is safe to say that the best work in geology has been 
done by those observers who have thus put themselves in a 
sympathetic relationship with the earth and have looked upon 
her as a great organism whose age is to be evaluated in pro- 
portion as her activities become known. The culture of the 
imagination is an academic bi-product. This argument of Pro- 
fessor Tarr would, then, as seriously militate against any im- 
portant modification of the lands by denudation as it does 
against that last stage where the forces of erosion have car- 
ried it down to a condition approaching a plain. The same 
criticism can be applied to his illustration of the slowness of 
geologic changes taken from the behavior of the Penobscot 
River in time of summer freshet. It is true that there is but 
little sediment in the running water of the stream, but does 
Professor Tarr deny that the neighboring mountain, Katahdin, 
has been worn out of an enormously greater terrane than that 
represented in the present mountain-root? We may note, in 
passing, that in any case the actual work of the Penobscot can- 
not be gauged by mere observations on a summer freshet ; it is 
in the spring, after the frost has loosened débris from the’ 
mountain-sides, that most of the transportation is effected for 
the year. 
2. The second objection referred to is more concrete and 
withal more scientific; yet it may be met in the same way. 
Each of many of the greater unconformities in the geologic — 
scale means a stand of the land long enough to remove almost 
completely a mountainous relief of surpassing magnitude by 
the self-same process of slow denudation as that characteristic 
of the lands to-day. Witness the pre-Palzeozoic land surface of 
the crystalline shield of Canada, the wonderfully even surface 
of the Archzean underlying the fossiliferous rocks of European 
