EARTH FEATURES SHAPED BY RUNNING WATER 171 



Point of 



Inflection 



FIG. 178. Hogarth's line of 

 beauty. 



178). The curve of beauty is now found in every section of the 

 hills, and it imparts to the landscape a gracefulness and a measure 

 of restfulness as well, which are not to be found in the landscapes 

 of earlier stages in the erosion cycle. In the bottoms of the 

 valleys also the initial windings of the 

 rivers within their narrow flood plains 

 add silver beauty lines which stand 

 out prominently from the more som- 

 ber background of the hills. 



Considered from the commercial 

 viewpoint, the mature upland is one 

 of the least adaptable as a habitation for highly civilized man. 

 Direct lines of communication run up hill and down dale in 

 monotonous alternation, and almost the only way of carrying a 

 railroad through the region, without an expenditure for trestles 

 which would be prohibitive, is to follow the tortuous crest of a 

 main divide or the equally winding bed of one of the larger valleys. 

 The final product of river sculpture the peneplain. When 

 maturity has been reached in the history of a river, its energies 

 are devoted to a paring down of the valley slopes and crests so 

 as to reduce the general level. From this time on hill summits 

 no longer fall into a common level that of the original upland 

 for some mount notably higher than others, and with increas- 

 ing age such differences become accentuated. There is now also 

 a larger aggradation of the valleys to form the level floors of 

 flood plains, out of which at length the now slight elevations rise 

 upon such gentle slopes that the process of land sculpture ap- 



proaches its end. Gradually 

 the vigor of the stream has 

 faded away, and can now only 

 be renewed through a fresh 

 uplift of the land, or, what 

 would amount to the same 

 thing, a depression of the base 



View of the old land of New level. Upland and river have 

 England, with Mount Monadnock rising reached old age together, and 



in the distance. , -, . . . 



the approximation to a new 



plain but little elevated above base level is so marked that the 

 name peneplain is applied to it. Scattered elevations, which be- 



FIG. 179. 



