July 10, 1896.] 



SCIENCE. 



43 



that in Cretaceous times the chief drainage 

 was down the faint dip of the strata to the 

 sovithwest, with longitudinal subsequent 

 branches along the strike of the weaker 

 shales ; but post- Cretaceous elevation being 

 greatest to the northwest, the southeast- 

 flowing subseqiTcnt streams graduallj^ gained 

 possession of the drainage and became the 

 chief rivers of the region ; the Des Moines 

 being an example of this kind. Diverted 

 consequent streams enter these masters 

 from the northeast ; headward-growing ob- 

 sequent streams enter from the southwest, 

 perhaps marking the reversed paths of for- 

 mer beheaded consequents ; the streams of 

 Warren county being chiefly of the latter 

 class. Faint escarpments facing northeast 

 are formed along the outcrops of the harder 

 strata. The larger streams have broad 

 flood-plained trenches below even uplands 

 of adolescent dissection ; but to cite these 

 trenches as examples of the ' immensitj^ of 

 erosion ' leaves no fitting term for the much 

 greater erosion by which the generally even 

 surface of the uplands was fashioned. 



GEOMORPHOLOGY OF NORWAY. 



Prof. Eduard Richter gives further ac- 

 count of his work last summer (See Science, 

 June 26), in his ^ Geomorphologische Beobach- 

 tungen aus Norwegen,^ contributed to the 

 "Vienna Academy (Sitzungsber., Feb., 1896), 

 from which a very clear picture of fjeld and 

 fjord may be gained. Much importance is 

 attached to the increased rate of weathering 

 in the belt above the limit of vegetation and 

 below the snow line. The plateau-like up- 

 lands are ascribed chiefly to this process, 

 and not to peneplanation during a lower 

 stand of the land, as advocated by some 

 authors. The mountains of Jotunheim are 

 regarded as unconsumed remnants of a 

 once much greater mass, now far advanced 

 in reduction to the upland level. Well 

 formed cirques (Botner) characterize the 

 later stages of this reduction, and many ex- 



amples are mentioned in various stages of 

 development. These forms are explained 

 as the result of retreat by weathering back 

 from a reentrant on which a protective 

 covering of neve or ice lies ; and thus ex- 

 plained, they are regarded as trustworthy 

 witnesses of former glacial action in various 

 mountains of middle Europe. As a special 

 feature of the Norwegian fiords, Eichter 

 emphasizes not only their U-shaped cross 

 section, but also the discordance of their 

 floor level with that of manj^ side valleys ; 

 the steep side- wall of the deeper fiord cut- 

 ting square across the floor of the shallower 

 side valley. This is ingeniously explained 

 as a modification of a preglacial valley sys- 

 tem by a glaciation of just such severity as 

 would fill some valleys with long ice 

 streams, while certain confluent valleys of 

 less and lower catchment area would be oc- 

 cupied by relatively inactive ice or only by 

 neve. The latter valleys would then be 

 little modified, while the former would be 

 rapidly deepened and changed from V to U 

 form. 



This essay is of particular interest in giv- 

 ing a clear analysis of the relation of form 

 to process, and in attributing much in- 

 fluence to the climatic control of denuda- 

 tion, both as determined by altitude above 

 sea level and as affected by glacial or inter- 

 glacial conditions ; but the sufliciency of the 

 process suggested for the production of the 

 uplands needs further demonstration. 



LITTLEDALE IN THIBET. 



Littledale's adventurous effort to reach 

 Lhasa is described in an entertaining narra- 

 tive with incidental mention of notable 

 physiographic features. A number of vol- 

 canoes were seen in Thibet south of Cher- 

 chen (mid-southern border of the desert of 

 Gobi). Thereabouts, the drainage from 

 the mountains enters salt lakes in flat inter- 

 montane depressions of great altitude. Fur- 

 ther southeast, rivers escape to the sea in 



