gO STUDIES FCR STUDENTS 
be) 
““orade’’ as a substitute for various paraphrases in my own work 
in 1893 (1894, 77). 
McGee considers the control of the balanced condition of 
rivers under the “ law of river gradation” (1891, 265). 
Mill uses ‘“‘grade”’ as a verb, essentially in the sense here 
advocated: ‘‘ Ultimately the river grades its course and flows 
uniformly along a uniform slope”’ (56). 
Gannett has adopted ‘“ grade” as a technical term in Folios 
1 and 2 of the Topographic Atlas of the United States. In the 
first he writes: 
There finally comes a time when the river ceases to erode, or rather, it 
deposits as much as it erodes. .... A river is then said to be graded. 
In the second, a special sheet with explanatory text is 
devoted to “A Graded River,” the example chosen being the 
lower Missouri : 
At this stage the lower portion of its [a river's] course has been eroded 
to almost as low a stage as possible, and its slope has become very slight, so 
that its cutting power is trifling. This part of the stream is said to be 
“« graded.” 
Johnson uses “gradation” as involving both degradation and 
aggradation, and as producing a ‘graded slope,” a slope of 
‘equilibrium easily disturbed, yet constantly maintained” (620). 
“Grade”? may therefore be regarded as having already 
gained recognition in the sense here advocated, as a replacement 
of one of the meanings of ‘ baselevel.”’ 
There remain to be considered several reasons in favor of 
giving different names to the limiting base of sub-aerial erosion, 
and to the balanced condition in which rivers spend most of 
their lives while approaching the limit of their work. The first 
reason is based on the persistence of the base level surface all 
through the cycle, without change from its initially complete 
extension, in contrast to the gradual introduction and slow 
extension of the condition of grade during the mature and older 
stages of the cycle. The second is based on the fixity of the 
baselevel surface in contrast to the variation in the slope of 
graded rivers. The third springs from the essential simplicity 
