= BASELEVEL, GRADE AND PENEPLAIN 99 
streams, whose behavior closely resembles that of graded water 
streams. 
The first development of the balanced or graded condition in 
waste streams usually takes place on the outcrops of the weaker 
rocks that are exposed on freshly cut valley sides. Here graded 
waste slopes are locally developed; the adjoining waste streams 
form a sheet or cloak of waste which creeps slowly down the 
slope, while untamed ledges of harder rocks are still kept bare 
by the removal of waste from their surface as fast as it is formed. 
These represent the falls and rapids of water streams, because 
the waste from above the ledges passes over them quickly; while 
the graded waste-covered slopes represent the graded reaches of 
water streams, where the movement is more regular and leisurely. 
The less resistant of the bare ledges are the first to retreat under 
cover, permitting the grades below and above to unite in a single 
_continuous slope; and so on, until all ledges are concealed under 
a graded sheet of waste, and the sharp, vigorous forms of youth 
and early maturity merge into the subdued and tamed forms of 
passing maturity and approaching old age.* During the progress 
of this change, there may be abundant examples of captures of 
one group of waste streams by the leading members of another 
group, especially in regions of tilted strata; thus increasing the 
resemblance of waste streams and water streams, until one is 
tempted to regard the difference between them as one of degree 
rather than of kind. 
As maturity passes into old age all the elevations are worn 
lower and lower and the graded cloak of waste covers more and 
mores Or, the suraces” (As the: later, stages’ of jthe:eyele are 
approached, the whole region, monadnocks excepted, is reduced 
to moderate relief and bare ledges are rarely seen. On the 
faintly sloping forms of advanced old age the graded sheet of 
waste covers the entire surface between the water streams. 
Everywhere gently waste-covered slopes lead from the low 
*I have pursued the comparison of water streams and waste streams somewhat 
further in my paper on “An Excursion to the Grand Canyon of the Colorado (1901, 
176). 
