December 19, 1912] 



NATURE 



445 



petuated during the general lowering of the valley- 

 floors. For those who do not know the details of 

 the ground, the argument seems to require further 

 development, since it may be urged that the large 

 meanders arose when the tributaries received much 

 more water from the drainage of the plateau, while 

 the Talauen represent the natural consequence of the 

 diminution in volume of the streams. The "misfit" 

 of a small meandering streamlet in a widely meander- 

 ing valley reminds us of the conditions of the Altmiihl 

 valley, near Eichstatt, which is believed at one time 

 to have held the Danube. An interesting account is 

 given (p. 164) of the changes that have taken place 

 where the Moselle traverses the sunken area of Witt- 

 lich. This depression is attributed to Middle Caino- 

 zoic earth-movements, and its form has become 

 moulded by the Moselle and its tributaries, which 

 have removed an immense amount of the yielding 

 Permian strata and have left courses illustrating dry 

 loops and river-capture. 



E. C. Andrews, in his " Corrasion b)- Gravity 

 Streams " (Proc. Roy. Soc. N.S. Wales, vol. xliii., 

 p. 204), has urged that running water may work out 

 a hollow in a valley-floor wherever its velocity is 

 increased, as occurs in a constriction of the valley. 

 The greater the velocity, the steeper will be the heads 

 of these hollows, and a series of steps may thus arise 

 in the floor, comparable to those found in valleys that 

 have been filled by ice. Andrews compares the reced- 

 ing heads of the waterfall-regions or torrent-regions 

 with the cirques (p. 282) of glaciated lands; the only 

 cirques considered by him, however, are those that lie 

 at valley-heads. He urges that rivers in flood-time 

 effect so abnormal an amount of denudation that 

 their normal action may be left out of count in con- 

 sidering the formation of their valleys. Similarly, the 

 glacial epoch gave rise to ice-floods, beside which 

 anything that we see now is insignificant (p. 274). 

 Glaciers are considered as a type of "gravity-stream," 

 and the author's studies in Australasia, California, 

 and Scotland, while they do not bring him to any 

 very new conclusions, lead to a pronounced advocacy 

 of the importance of glacial erosion. In vol xliv., 

 p. 262, Andrevi's illustrates the formation of steps and 

 roches moutonnees by plucking action in the Yosemite 

 valley. We do not know why (p. 292) he writes the 

 extraordinary words, "lee seites " and " stoss seites," 

 when he has used the convenient adjectives " down- 

 stream " and "upstream" in his previous paper. 

 Here, again, cirques are regarded, not as arising in- 

 dependently on an upland by the corroding action of 

 frost, but merely as the faces of steps formed beneath 

 an ice-flood (p. 305), which have retreated upstream 

 to their present positions on divides. In vol. xlv., 

 p. 116, the author discusses "Erosion and its Sig- 

 nificance," and points out that where two peneplane 

 surfaces in association are separated by youthful topo- 

 graphy, tectonic movements must have produced the 

 difference of level. The flood-question is again dis- 

 cussed. 



P. Morin, of MontluQon, reviews "Le probl^me de 

 1 'erosion glaciaire " in the Revue ginirale des 

 Sciences for 191 1, p. 762. He shows how the rock- 

 ridges in the centre of some glaciated valley-floors, 

 ■which ^re quoted by Brunhes as evidence of the in- 

 efficiency of the ice, may arise from a union of 

 glaciers along aretes which they have not been able 

 to remove. Others represent the central parts of 

 rock-barriers that lay athwart the ice-flow, the more 

 rapid erosion by frost action and plucking on the 

 margins of the glacier having excavated their ends 

 more rapidly. The paper is agreeably illustrated, and 

 sections are given on a true scale of the floors of 

 glaciers descending from Mt. Blanc. 



NO. 2251, VOL. 90] 



The late Prof. R. S. Tarr, who made a special 

 province of Alaska, gave a general account of its 

 glacial features in Science for February 16, 1912. 

 The burden of sediment in the streams flowing from 

 the glacier-margins led him naturally to ask (p. 250), 

 "Can there be any doubt but that the glacier which 

 protects the rock against the atmospheric agencies 

 must attack it with equal or even greater vigour?" 

 We may, perhaps, refer back to his excellently illus- 

 trated paper on "Some Phenomena of the Glacier 

 Margins in the Yakutat Bay Region, Alaska " (Zeit- 

 schrift fiir Gletscherkunde, Bd. iii., p. 81), which has 

 enabled many of us to compare outwash-features with 

 those traceable in the British Isles. The results of 

 glacial advance over old deposits are also clearly in- 

 dicated (p. 102), and a warning is given against inter- 

 preting layers of vegetation interbedded with glacial 

 detritus as evidence of an interglacial epoch. "A 

 slight forward motion may weU have pushed a broken 

 ice-margin out into the fringing forest," as it did 

 before the author's eyes in the Malaspina region in 

 1906. 



O. D. von Engeln, of Cornell University {ibid., 

 I Bd. vi., p. 104), records the results of observations 

 I made in Alaska on "Glacier Drainage and Wastage" 

 during two expeditions led by Prof. Tarr. Much 

 interest attaches to the forcing up of marginal streams 

 against the valley-sides (p. 128) when a glacier in- 

 creases in width ; rock-gorges are then cut, parallel 

 to the sides, which may easily again run dry. It is 

 shown (p. 142) how denudation is rapid in an ice- 

 filled valley, even if we neglect the erosive action of 

 the ice, since the removal of the material copiously 

 avalanched from the valley-walls leaves the surfaces 

 continuously open to attack. 



G. W. Lamplugh has published in the Proceedings 

 of the Yorkshire Geological Society (Leeds, vol. xvii., 

 p. 216) an important paper on the shelly moraine 

 pushed up by the Sefstrom Glacier from the sea-floor 

 in Spitsbergen in i8g6. The illustrations selected are 

 of exceptional beauty, apart from their geological 

 value as Arctic landscapes. 



W. von Lozinski usefully discusses " Die peri- 

 glaziale Facies der mechanischen Verwitterung " 

 (Naturwissenschaftliche Wochenschrift, October 8, 

 19 11). The traces of widespread weathering by frost 

 are destined to disappear as the conditions of the 

 Ice age recede from us. The breaking up of rock- 

 surfaces into block-detritus by frost must have 

 occurred on an enormous scale as glacial conditions 

 spread, and the material thus loosened provided the 

 abundant erratics that were carried by the ice-invasion 

 into the lowlands. Similar block-formations arose as 

 the ice retreated, and also in unglaciated lands sub- 

 ject to its chilling influence; these detrital masses 

 of local origin cumber the surface of large parts of 

 Europe at the present day. 



R. A. Daly (Amer. Journ. Sci., vol. xxx., p. 297) 

 publishes a characteristically speculative but sugges- 

 tive paper on "Pleistocene Glaciation and the Coral- 

 reef Problem," in which he represents the existing 

 reefs as arising on a plateau of marine denudation, 

 which was formed when the sea-level was lowered 

 by the abstraction of its waters to form continental 

 ice. 



Those who wish to follow the course or courses of 

 opinion on the origin of Ice ages will find a good 

 review and a new cosmic suggestion in Fr. Nolke's 

 paper, "Die Entstehung der Eiszeiten " (Deutsche 

 geographische Blatter, Bd. xxxii., p. i.). The 

 passage of the sun through a heat-absorbing nebular 

 aggregate is invoked. Ach. Gr^goire (Bull. Soc. 

 Beige de Geologic, tome xxiii., p. 154) believes that 

 the elevation of a sea-floor to form a continent brings 



