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SCIENCE 



[N. S. Vol. XXVII. No. ( 



mislead the student, inasmucli as uplift 

 might be going on in a young, a mature 

 or even an old mountain range; while up- 

 lift might have entirely ceased in a young 

 mountain range. The stages of mountain de- 

 velopment are not directly concerned vcith con- 

 structional forces, but depend wholly upon the 

 amount of dissection accomplished by destruc- 

 tional forces. 



If the author's statements are correctly in- 

 terpreted, it would seem that the stage of de- 

 velopment of the land form and the stage of 

 stream development are often confused. On 

 page 132, after describing a region where the 

 streams " dash swiftly through narrow 

 canyons " and where " rapids and waterfalls 

 mark their courses," it is stated that " the 

 topography has now reached its mature stage." 

 It is true that the land form in question may 

 have reached maturity, but the description 

 suggests that the streams are very young. 

 Figure 98 represents the head of King's Eiver 

 in the Sierra Nevada, and is given as an 

 example of " topography in early maturity." 

 The mountains are mature, hut the valley ap- 

 pears to be young. Figure 99, Trinity Eiver 

 in the Klamath Mountains, and figure 100, a 

 ■ canyon near Phoenix, Arizona, are likewise 

 cited as "examples of "mature topography," 

 although both show features generally regarded 

 as characteristic of youth, and both are re- 

 ferred to as " canyons." 



The discussion of drainage patterns on pages 

 143-151 is confusing, because the author uses 

 the terminology of recent students of river ac- 

 tion, but does not follow their interpretations. 

 The definition given of subsequent streams is 

 not the definition generally accepted by physi- 

 ographers, and the origin of subsequent 

 streams as understood by them is nowhere re- 

 ferred to. The figure representing subsequent 

 streams is misleading inasmuch as none of the 

 streams can be regarded as subsequent, with 

 the very doiibtful exception of a few of the 

 smallest branches. The request that the stu- 

 dent distinguish between the consequent and 

 subsequent streams of the folded Appalachians 

 may lead to error, for the streams (Delaware, 

 Susquehanna, etc.), which according to the 

 implication of the text are to be considered 



consequent, are believed by those most familiar 

 with the rivers of the region, to belong to a 

 different class. The statement that " the 

 tributary streams are, however, weaker than 

 the rock structure and have adapted them- 

 selves to it," and that stream channels are 

 " slowly shifted to correspond to the differ- 

 ences in the rocks " suggests that the streams, 

 tributaries and all, are ready made, let down 

 upon diverse rock structures, and then bodily 

 shifted to follow the softer rocks as far as 

 possible. The student is here given an inter- 

 pretation of the methods of drainage adjust- 

 ments quite different from that generally ad- 

 vanced to account for the relations existing 

 between longitudinal and transverse valleys. 

 One is surprised to find in a modern text-book 

 the statement that when subsequent streams 

 '' encounter a broad stratum or dike of re- 

 sistant rock, they turn and follow along the 

 softer beds by the side of the main stratmn 

 until a narrow or weak spot is found in it, and 

 then they turn and cross" (p. 145). Such an 

 explanation is obsolete. 



On page 190 we find the statement that 

 " Plains of accumulation are distinguished by 

 perfectly even surfaces, often many miles in 

 extent. Volcanic plains and plains of ero- 

 sion are often undulating." Maturely dis- 

 sected plains and plateaus have no place in 

 this classification, and the undulating surfaces 

 of young plains of accumulation are not 

 recognized. The Appalachian Plateau is not 

 even mentioned in the discussion of plains 

 and plateaus of the United States ; nor under 

 mountains formed by erosion, where other dis- 

 sected plateaus are classed. But under Rivers 

 of the United States, we find a brief reference 

 to the " maturely dissected " Appalachian 

 Plateau (p. 347). The region from the head 

 of the Gulf of California eastward into Texas 

 is described under Marine Plains (p. 193), 

 where it is stated that " the waves and cur- 

 rents which built up these plains so long ago 

 distributed the sediments as evenly as a floor. 

 The mountain peaks rise like islands from 

 this floor." The alluvial origin of extensive 

 areas of the intermontane plains, the relations 

 of the plains to each other and to the moun- 

 tain ranges, and the many other complications 



