84 National Geographic Magazine. 
There is a curious intermediate type of drainage lately recog- 
nized by McGee in the southern states, a superimposed drainage 
that is not inconsequent upon the buried surface beneath the 
unconformably overlying surface layer. It occurs in regions 
where a well-marked drainage had been established ; a brief sub- 
mergence then allowed the deposition of a relatively thin mask 
of sediments; an elevation brought the masked surface up 
again, and as it rose, the streams took possession of lines essen- 
tially identical with the courses of their ancestors, because the 
mask of newer deposits had not extinguished the antecedent 
topography. McGee proposes to call such streams “resurrected.” 
Rivers of all classes as a rule develop during their adolescence 
and more mature .growth certain “subsequent” branches that 
were not in any way represented in the early youth of the system. 
Thus the indefinite members of the consequent drainage of the 
Jura mountains have developed subsequent streams on soft beds 
of monoclinal and anticlinal structures, where there could not 
possibly have been any consequent drainage lines at the birth of 
this system, unless we admit the supposed fracturing of the anti- 
clinal crests, which seems unnecessary to say the least. Even in 
the simplest style of drainage, growing on a level surface, many 
of the branches must be “subsequent,” or as McGee has called 
them in such cases, “ autogenetic.” 
Rivers of all classes are subject to spontaneous re-arrangement 
or adjustment of their courses to a greater or less extent, in ac- 
cordance with the weaker structural lines. This results from the 
migration of divides and the consequent abstraction or capture 
of one stream by another. The capture is generally made by the 
headward development of some subsequent branch. But after 
this kind of change has advanced to a certain extent, the divides 
become stable, and further change ceases. The rivers may then 
be said to be maturely adjusted. Under certain conditions, 
chiefly great initial altitude of surface, and great diversity of 
structure, that is, in mountainous regions, the changes arising 
from adjustments of this spontaneous kind are very great, so that 
the courses of a river’s middle age may have little resemblance to 
those of its youth, as Léwl has pointed out and as I have tried to 
show in the case of the Pennsylvanian rivers. It may be difficult 
to recognize in such cases whether the youthful courses of a river 
system were consequent, antecedent or superimposed. Adjust- 
ments of this kind were not discussed by Powell, although he 
