652 



SCIENCE. 



[N. S. Vol. I. No. 24. 



or eight kilometers broad, so as to slope 

 toivards instead of from the Alps ; aud the 

 deformation of the Deckenscliotter and of the 

 earlier higher terraces is greater than that 

 of the lower and younger terraces, thus 

 proving the progressive action of the de- 

 forming forces. Associated with this change, 

 there was a general depression of the Molasse 

 belt, between the Jura and the Alps, and in 

 the depressed part of the valley of the 

 Limmat, thus generally outlined by the 

 latter process and locally deepened by the 

 former process, the lake had Its birth. 

 The belt in which the terraces are deformed 

 crosses the valley somewhat obliquely, but 

 runs parallel to the strike of the general 

 Alpine deformations of the region. Into 

 the lake thus formed, the glaciers of the 

 second and third epochs advanced ; but 

 they exercised so little destructive power 

 that they did not obliterate the terraces on 

 the valley sides. The lateral moraines of 

 the last epoch are distinctly discordant with 

 the terraces ; the moraines reaching succes- 

 sively higher and higher terraces up-stream, 

 and crossing the belt of deformation with- 

 out indication of disturbance. Outside of 

 the several terminal moraines, the former 

 lower end of the lake received the valley 

 gravels that were washed fi-om the ice. 

 Hence while the later glaciers may have 

 acted to some degree in altering the form of 

 the lake, their chief effect was to diminish 

 its size by supplying plentiful gravels from 

 the inner Alps, with which a part of the 

 lake basin that they entered was filled. 



TARNS OF THE ENGLISH LAKE DISTEICT. 



J. E. Maer has examined the tarns or 

 smaller lakes of the mountainous district of 

 northwest England, and finds that their re- 

 puted dependence on rock basins is not jus- 

 tified by local study. They appear to re- 

 sult from drift obstructions, bj^ which their 

 outlets have been turned to one side of the 

 former valley troughs and detained in dis- 



charging the lakes by settling on rock ledges. 

 In many cases lakes of similar origin have 

 been converted into meadows when their 

 outlets did not depart greatlj^ fi-om the for- 

 mer vallej' line, and hence encountered only 

 drift in trenching new discharging channels 

 (Quart. Jour. [London] Geol. Soc, li., 

 1895, 35—48). TMs does not bear so much 

 on the general question of glacial erosion as 

 on the particular question of the ability of 

 glaciers to form basins by local erosion in ex- 

 cess of their general action along their floor. 



THE REGION ABOUT MUNICH. 



In celebration of its twenty-fifth anniver- 

 sary, the Geographical Society of Munich 

 has issued a handsome volume of 4-40 pages, 

 containing a number of essays bj^ Giinther, 

 Ratzel, Penck and others. Ratzel makes 

 the coast line of Maine 4,300 miles in actual 

 length ; though a direct line from Eastport 

 to Kittery measures only about 200 miles. 

 The essay most likely to interest American 

 readers is on the geology of the region 

 about Munich by Ammon, illustrated with 

 a geological map, plate and cuts. It may 

 serve as a guide to excui'sions from this at- 

 tractive center ; from few other points can 

 so manjr phases of piedmont glacial geology 

 and geography be seen to so good advan- 

 tage. "Wiirm and Ammer lakes lie twenty 

 odd miles to the southwest, enclosed by the 

 younger morainic belt. Older moraines 

 stretch farther out fi-om on the plain, es- 

 pecially to the east of the city ; and bej^ond 

 them are' spread the flat confluent gi-avel 

 fans that are associated with various epochs 

 of ice advance. On the sloping plain stands 

 Munich, and across it the Isar and the Am- 

 per have trenched their new valleys. The 

 illustrations of morainic topography are 

 very characteristic. A good bibliography 

 accompanies the article ; while on an ear- 

 lier page, Simonsfeld contributes a thirty- 

 page Bibliotheca geograpJiica bavarica. 



Haevaed Univeesity. W. M. Davis. 



