BASELEVEL, GRADE AND: PENEPLAIN gI 
in the meaning of ‘“baselevel,” in contrast to the complexity 
and variety of conditions ultimately gathered under the term 
Sorade. 
Baselevel ts complete from the beginning, and permanent to the 
end; Grade ts slowly introduced and gradually extended.—The con- 
ception of the general baselevel must be made at the outset as 
that of a completed surface extending beneath the land mass 
under consideration at the beginning of the cycle, and so remain- 
ing as long as the advance of the cycle continues undisturbed. 
In the ideal case, which provides the general scheme with res- 
pect to which all other cases are classified, the land mass once 
uplifted is supposed to stand still until it is worn down flat. 
This supposition is so artificial, and does so great violence to 
much that is known as to the behavior of the earth’s crust, that 
some students are therefore disposed ‘to discard the scheme of 
the cycle altogether in the study of the sculpture of land masses, 
overlooking the fact that however many movements of a land 
mass may be discovered, the many incomplete cycles that are 
separated by these movements must each be treated essentially 
according to the scheme of the ideal cycle. In every case, the 
processes of land sculpture, quickened or slackened in conse- 
quence of the new attitude given to the region, go on with 
respect to the new attitude of the baselevel within the land 
mass. 
Even during the movement of the land mass, it must be con- 
ceived of as rising orsinking through a fixed and complete base- 
level surface, with respect to which its carving is even then 
begun, and long afterwards continued, during the ensuing time 
of relative or absolute rest. Hence, for every cycle or partial 
cycle of erosion, the imaginary baselevel surface is immediately 
conceived as complete at the outset, and as thenceforwards 
remaining unchanged. Local baselevels are also complete, in 
extending at once as far as the imagination wishes to carry 
them; they rise or fall slowly with their control. 
It is far otherwise with the development of the graded con- 
dition. The previous paragraphs have explained that the devel- 
