BASELEVEL, GRADE AND PENEPLAIN 105 
employment of the term with double meaning by Hughes, in 
describing the uplands of western Yorkshire : 
It is to both of the agencies above mentioned [marine and subaerial 
erosion], acting simultaneously throughout long ages, that we must refer the 
tremendous results that we have forced upon our attention. ... We will 
refer to these great plateaux by the shorter term sea-plain; to distinguish 
them from the river-plains or bed-plains (131). 
Dryer uses the phrase, ‘‘ graded plain,” in a somewhat 
different sense. The reduction of the border of a land area 
to a submarine plain by sea action, while the rest of the 
land surface is reduced to ‘‘ baselevel”’ by subaerial processes, 
would result in the production of a ‘graded plain, lying 
partly above and partly below sea level” (234). No example 
of this kind of plain is mentioned. Gradation plain is used by 
Adams for a locally developed peneplain between residual 
ridges (508). 
The terminology employed by Hayes departs somewhat from 
that in use with other writers. He says: 
The processes which tend to produce a baselevel plain are embraced 
under the term gradation. This includes aggradation and degradation. 
.... A baseleveled surface is any land surface, however small, which has 
been brought approximately to a baselevel, either general or local, by the 
processes of gradation. When such a surface has considerable extent it 
becomes a baselevel plain. .... The term daselevel peneplain or simply 
peneplain is applied to a surface of which a greater or less proportion has 
been reduced to the condition of a baselevel plain, but which contains also 
some unreduced residual areas (21, 22). 
It seems to me that it is going too far to say that ‘‘a base- 
level surface is any land surface, however small, which has been 
brought approximately to a baselevel, either general or local.” It 
would follow from this definition that, inasmuch as every point ina 
continuously graded river is a local baselevel for every other point 
further up-stream, the upper stretches of the flood plain or broad 
valley floor of a large river would be called a baselevel surface, 
in spite of their standing several hundreds or even thousands of 
feet above the general baselevel. The valley plain of the Platte, 
for example, attains altitudes of more than 3,000 feet, and can- 
not be fitly described as a baselevel plain, unless baselevel is 
