May 20, 1898.] 



SCIENCE. 



705 



Sound,' by Willis (Bull. Geol. Soc. Amer., 

 IX., 1898, 111-162), who after a study of 

 the region concludes that it was invaded by 

 confluent glaciers from mountains on the 

 north, east and west, and that the spaces 

 between the ice streams were built up by 

 washed drift. Plateau-like land-arms were 

 thus constructed with relatively even up- 

 land surfaces and smooth marginal slopes, 

 while the glaciers held possession of the 

 troughs. When the glaciers melted away, 

 the troughs came to be occupied by arms of 

 the sea. Lateral moraines along certain of 

 the troughs prove that they antedate the 

 latest epoch of glaciation, and are not chan- 

 nels of post- Pliocene erosion. The greater 

 depths of certain troughs some distance in 

 from their outer end does not accord with 

 the idea that they are drowned valleys of 

 stream erosion. Since the disappearance 

 of the ice, alluvial deposits brought down 

 by the larger rivers have formed delta 

 flood plains in a number of the troughs, 

 such as those of Duwamish and Puyallup 

 valleys, by Seattle and Tacoma. 



THE PLAINS OF RUSSEA. 



Das eussische Flachland forms the 

 subject of an interesting sketch by Phil- 

 ippson (Zeitschr. Gesell. f. Erdk. Berlin, 

 XXXIII., 1898, 37-68), from which the 

 leading features of that great region may 

 be easily gathered. Paleozoic strata, nearly 

 horizontal and but moderately indurated, 

 rest upon a crystalline floor that appears on 

 the northwest and southwest ; Mesozoic 

 and Tertiary strata overlap irregularly, 

 chiefly from the southeast. Bevelling far 

 and wide across these varied formations 

 stretches the upland plain of comparatively 

 even surface at an altitude of 200-300 

 meters. The northwestern part of the 

 plain is heavily covered with glacial drift, 

 through which the bed rock is seldom seen ; 

 the southern part has a loess mantle, which 

 overlaps the border of the drift. The for- 



mer is the region of forests ; the latter, of 

 steppes ; the ' black earth ' being a modifi- 

 cation of loess by the superficial addition 

 of humus. The plain beneath these dis- 

 crete covers is described as a gigantic ' de- 

 nudationsflache, ' the result of the lateral 

 shifting of great rivers when the land stood 

 lower than now ; and the question is raised 

 whether the floods from melting ice fields 

 may not have supplied the great rivers. 

 To-day the plain is dissected by narrow 

 valleys of branching streams, and from 

 this an uplift is inferred subsequent to the 

 peneplanation. 



The insular j)Osition of Great Britain has 

 been recognized by British geologists and 

 geographers as giving rise to an over-esti- 

 mate of the relative value of marine as 

 compared to sub-aerial denudation. May 

 not the relatively modern block- dislocations 

 of the uplands and mountains of Germany, 

 where many areas of resistant rocks are 

 included, and where an advanced stage of 

 base-levelling has not been reached in the 

 present cycle of erosion, have given rise to 

 an under-estimate of the competency of 

 normal rivers to produce peneplains. Such 

 general denudation is aided truly enough 

 by the lateral shifting of the larger streams, 

 but it is accomplished chiefly by the slow 

 weathering of the inter- stream hills. Does 

 it not hurry the slow processes of penulti- 

 mate denudation to imply that they may 

 have been accomplished in so brief an epi- 

 sode as a glacial period, and by so tempor- 

 ary an agent as the floods from a melting 

 ice sheet ? 



TIDAL PROBLEMS. 



The difiiculty of accounting for the actual 

 tides of the oceans, in contrast to the ease 

 of explaining the lunar and solar forces to 

 which they are due, is well set forth in an 

 inaugural address 'Ueber Gezeitenwellen,' 

 by Kriimmel, on his accession to the rec- 

 torate of the University of Kiel (Ann. der 

 Hydrog., XXV., 1897, 337-316). Among 



