BASELEVEL, GRADE AND PENEPLAIN 79 
The third certainly referred to the faintly sloping reach of a 
river, and not to a level surface passing through the ledge of 
hard rock with respect to which the reach is worn down, 
although this latter meaning has become popular. The follow- 
ing citations will show that most writers seem to be agreed that 
baselevels may be local or temporary as well as general, but that 
there is no prevalent agreement as to the definition of either the 
general or the local baselevel. 
Definitions of “baselevel” by various writers—The following 
authors adopt the first of the above meanings. Gilbert writes: 
The land cannot be worn down below the level of the ocean. Geologists 
express this law by saying that the ocean is the “‘baselevel of erosion”’ (1896, 
575). 
Campbell says: 
If the streams are in their old age, the surface of the land will constitute 
a peneplain, and in their extreme old age, this peneplain will approach very 
closely to baselevel (665). 
Tarr writes to the same effect: 
In no part of the valley can the stream cut below the sea level, or below 
baselevel, as it is called (265). 
Russell quotes Powell, as if adopting his definition, but con- 
cludes that : 
The real baselevel toward which all streams are working is the surface 
level of the sea. . . . When a stream has lowered its channel nearly to base- 
level, downward corrasion is retarded, but lateral corrasion continues. ... The 
ultimate result of erosion is to reduce a land area to a plain at sea level 
(47-48). 
Finally, Powell may be quoted again as follows: 
The baselevel of a plain is the level of the surface of the sea, lake or 
stream, into which the waters of the plain are discharged (1895, 34). 
The second idea under the term ‘'baselevel’’—that of the 
imaginary undulating surface—does not appear to have been 
adopted by any of the many writers whose works I have looked 
over. It is perhaps on account of the elaborateness of this 
second meaning that it has not come more generally into use. 
Its partial adoption, however, is indicated by the following 
