153 
THE NORTHERN PACIFIC ROUTE. 
but the evenness of its summits, as if the region were a vast plateau. 
As this is the country through which the westbound traveler has 
just come, he appreciates that such is not the case, but the moun- 
tains are made up of ridges of nearly the same height, the tops of 
which, at a distance, blend so as to appear like a flat-topped mountain. 
The even crests of such ridges and mountains are supposed to 
have been formed when the land was low lying and in fact nearly 
a plain (a peneplain).1_ At that time there were no mountains in 
this region and the surface was as flat as the prairies of North Dakota 
and probably much nearer sea level. 
For some distance after crossing Pend Oreille Lake the railway 
skirts the base of the mountain on the left (east), and the cuts through 
the low spurs reveal the granite in many places. On some of these 
ledges, even from the moving train, glacial striz (scratches in the bed- 
rock made by rock fragments embedded in the ice and forced along 
under enormous pressure) may be seen. The direction of these 
scratches is parallel with the a and shows that the glacier 
moved up the valley toward Spokan 
The railway crosses the valley, ouittinc through many knolls of 
gravel and sand deposited by a stream which flowed from the end of 
' The constant tendency of almost all 
natural processes going on at the surface 
of the earth is to wear away the high 
land and to reduce the continent toward 
sea level. 
surface of the land would be reduced to 
a plain were there no counteracting forces 
at work. The forces that tend to inter- 
fere with the reduction of the surface of 
the earth are those that produce move- 
ment within the crust, for such move- 
ments are almost always accompanied by 
elevation at some point, and when this 
again. If, however, crustal movements 
do not occur for a long time, the surface 
of the earth is reduced nearly to a plain 
that stands near but not at sea level. 
Such a surface has been named a pene- 
plain (meaning ‘‘almost a plain”). In 
most regions the process of reduction in 
the past has been interrupted by the 
pee eg of those particular parts of the 
surface was greatly 
ca but in certain places the proc- 
ess seems to have been carried nearly 
to its limit and a peneplain produced. 
If after the formation of such a pene- 
plain the land is uplifted evenly over a 
wide area, the peneplain, instead of 
being near sea level, will form an upland 
or plateau. As such an elevated tract is 
always vigorously attacked by streams, 
canyons will soon be cut back from the 
edge of the plateau or from the mouths 
of the streams, and, as time goes on, 
these canyons will reach farther and 
farther back into the upland and new 
the fact that the region has lost its even 
surface, the hills or mountains will have, 
for a long time, about the same height,’ 
and their summits will be but little 
below the surface of the old peneplain. 
In other words, the country is a di 
plateau, but to an rg at a distance 
the even i the ridges still 
appear like the level Bal of the plateau. 
