194 



SCIENCE. 



[N. S. Vol. XVII. No. 422. 



being ' practically down to grade.' The Osage 

 pi-airies, lying next west, present a series of 

 ragged, east-facing rock-terraces and outliers; 

 the sinuous retreating escarpment of resist- 

 ant limestones and sandstones, between which 

 the weaker strata are worn to fainter relief. 

 To the north, this area is blanketed with old 

 drift, now dissected sufficiently to reveal 

 patches of the underlying rocks. South of 

 the center of the state is the Great Bend 

 lowland, an extensive plain, more or less 

 mantled with sands, close to the level of the 

 Arkansas river, which flows through it; the 

 plain has been eroded on weak shales, and is 

 bordered by uplands of harder rocks. After 

 several other areas, the High plains of the 

 western third of the state close the essay; this 

 division of the Great plains is described as 

 still largely of constructional origin, its val- 

 leys being relatively small furrows when com- 

 pared with the great extent of level upland re- 

 maining between them. 



It is in this western and semi-arid part of 

 Kansas that the summer traveler from rainier 

 lands is surprised to recognize the rivers in 

 the distance by the clouds of sand blown up 

 from their dry channels: a peculiarity which 

 has suggested the remark that ' one seldom 

 sees rivers whose beds are so well aired as 

 those of the Great plains.' 



THE ALPS IN THE ICE AGE. 



' Die Alpen im Eiszeitalter,' by Penck and 

 Briickner, of which four parts have now ap- 

 peared (Leipzig, Tauchnitz, 1901-2, 432 pp., 

 many illustrations), promises to be a thor- 

 ough and trustworthy monograph. The most 

 notable characteristic of the work, as far as 

 it is now published, is the admirably broad 

 basis of fact upon which its generalized in- 

 ductions are based. Many of these are of 

 physiographic import. It is shown, for ex- 

 ample, in the section on the northeastern Alps 

 that the larger valleys repeatedly present a 

 systematic succession of features for which 

 glacial erosion and deposition are taken as 

 the cause. These features are impressed upon 

 a region which in preglacial time is believed 

 on good reasons to have been a mountain mass 

 of rounded forms, whose valleys opened north- 



ward upon a piedmont peneplain. Most im- 

 portant among the glacial features are the 

 cirques of the valley heads, by whose excava- 

 tion the subdued preglacial mountain masses 

 were given sharp peaks and aretes (as shown 

 by Richter) ; the over-deepened main-valley 

 troughs, with over-steepened lower side-walls 

 and with discordant or hanging side-valleys; 

 moraine-walled basins near where the over- 

 deepened valleys broaden and open on the 

 piedmont plain; groups of drumlins inside of 

 the moraines, and extensive sheets of gravel, 

 now more or less terraced, outside of the 

 moraines. The repeated examples of these 

 features, described, illustrated and mapped as 

 occurring in orderly fashion in one valley 

 system after another, are most instructive and 

 convincing. Those who desire to review the 

 work of ancient glaciers in the Alps can not 

 do better than provide themselves with this 

 excellent monograph as a guide for a fort- 

 night's excursion in one of the valleys of the 

 Tyrol. 



It should be noted that these authors, and 

 others of the same mind, have been led to 

 conclude that large glaciers of strong slope 

 deeply erode their valleys, not because of the 

 discovery of any new facts regarding the 

 erosive action of existing glaciers, but be- 

 cause of the unanimous testimony to this con- 

 clusion by the witnesses of glacial action in 

 the past. Regions of extinct glaciers are 

 unanimous in testifying to the repeated oc- 

 currence and systematic distribution of the 

 features above named in their larger valley 

 systems, while non-glaciated regions are 

 equally unanimous in testifying to their ab- 

 sence. At the same time, well-grounded 

 generalizations as to the normal development 

 of valley systems by rain and rivers exclude 

 Alpine cirques, over-deepened main valleys 

 and hanging lateral valleys, basins, drumlins 

 and moraines from among the possible fea- 

 tures of such systems; while generalizations 

 as to the modification of normal valley sys- 

 tems by temporary glacial action, on the as- 

 sumption of active glacial erosion, logically 

 demand the occurrence of precisely such fea- 

 tures. Little wonder then that the theory 

 of strong glacial erosion has found increasing 



