MAPS AS GEOGRAPHICAL ILLUSTRATIONS 511 
These uplands are among the best examples that I have seen 
of worn-down mountains, now lifted and slightly dissected, but 
still retaining over broad areas the form to which they had been 
reduced while they yet stood close to the former baselevel of 
the region. The Rhine has cut its gorge directly across the 
uplands, and when this is taken in connection with its behavior 
on the open valley further south, it indicates very clearly the 
existence of the Rhine as a river antecedent to the differential 
movements by which the bread outlines of the present geography 
were determined. 
That the Rhine actually flowed across the country that is 
now raised to an upland position is demonstrated by a more 
minute study of the form of its present valley; this study being 
made, however, much more easily on the ground than by means 
of the maps. A broad trough is sunk to a depth of about a 
hundred meters beneath the general level of the upland. On the 
floor of this trough is a level deposit of loess lying upon water- 
worn shingle, which in turn rests upon the bedrock. The pres- 
ent gorge of the Rhine is a narrow trench that is incised about 
250 meters beneath the loess-covered floor of the trough. The 
path of the Rhine in its gorge is much less sinuous than that of 
the Moselle on the west and the Lahn on the east. It is possible 
that this difference of behavior may be explained as the result 
transverse course of the larger river, and of the longitudinal 
courses of its side branches. During the former cycle of denu- 
dation the longitudinal streams would generally have had wider 
valleys and better chances to meander on their floors than the 
transverse Rhine could have had; and the result of their former 
meandering on flat valley floors is now seen in the meandering 
path of their steep-sided gorges. 
Following the lead of the larger rivers, the smaller side 
streams are actively at work dissecting the upland; but as yet 
they have seldom made much progress in their work. It is 
noticeable that upon the uplands of the Hunsrtck three streams 
now flow south or southeast through the residual ridges of the 
Soonwald on their way to the Nahe and the Rhine, thus suggest- 
