March 8, 1895.] 



SCIENCE. 



259 



sistiiig of sand, gravel aud bowlders, has 

 been piled in great masses at the points 

 where the streams enter upon the lower 

 plains." If it were not for the earlier ac- 

 count of these huge fans by Hilgard (Bull. 

 Geol. Soc. Amer., iii, 1S»1, 124) they could 

 hardly be recognized here. In Arizona 

 we read that the irrigating streams are 

 largely supplied by rains induced by the en- 

 forced ascent of the winds when they en- 

 counter the precipitous and ragged fault 

 scarp, where the great plateaus rise out of 

 the lower desert plains. In Idaho a great 

 e.vpanse of dissected eountrj', w-here the 

 rivei"S have cut down deep valleys, cannot 

 be irrigated without expensive engineering 

 operations ; but farther up the Snake River, 

 '■ where the streams have not j^et succeeded 

 in cutting through the lava," the river 

 water can be distributed over the plain with 

 comparative ease. ' Yet ' is a most ex- 

 pressive word for the geographer. The 

 whole report is full of suggestive examples 

 for exti-act and quotation. 



BAYS AXD FIORDS KEGARDED AS SUBMERGED 

 VALLEYS. 



Early writers generally ascribed bays 

 and fiords to the destructive action of the 

 sea, or to local dislocation. Esmark, about 

 1826, was perhaps the first to ascribe much 

 importance to ice as an agent in making the 

 Nonvegian fiords; a suggestion that was 

 aftei-ward carried to an extravagant ex- 

 treme. Dana, on returning from the "Wilkes 

 expedition, introduced the idea that fiords 

 are drowned valleys ; but whether the ero- 

 sion of the valleys was done by ' river work 

 alone, or more or less by glaciers,' must be 

 determined bj' local study. In the present 

 view of the problem, glacial erosion is 

 almost by general consent reduced to a 

 moderate measure ; it is chiefly the fiord 

 basins that are now attributed to ice action, 

 while fiord valleys are regarded by nearlj' 

 all observei-s as of preglacial origin as ordi- 



nary land valleys, afterwards submerged. 

 Bays, like Chesapeake and Narragansett, 

 are commonly regarded as resulting from 

 the submergence of wide river valleys, modi- 

 fied by glacial erosion or deposition, if in 

 glaciated regions. This modem view is 

 lately reenforced in an article by Professor 

 Shaler (Evidences as to change of sea level. 

 Bull. Geol. Soc. Amer., vi., 1SS5, 141-166), 

 in which various reentrants of our coast, 

 such as Chesapeake and Narragansett bays, 

 the fiords of Maine, and the numerous de- 

 pressions which break the northern part of 

 the continent into a group of islaiuls, are all 

 ascribed wholly or chiefly to the submerg- 

 ence of stream- worn lands. The general 

 problem of submergence seems, however, 

 hardly so simple as ' to indicate a progres- 

 sive subsidence of a somewhat uniform 

 nature ' along the Atlantic coast from Mexico 

 to near the pole. The possibility of numer- 

 ous subordinate and discordant oscillations 

 in different parts of the coast is wide open ; 

 and while in a general way it may be said 

 that our eastern coast has been depressed, 

 it does not follow that the depression was 

 sj'uchronous throughout, as it must have 

 been if its cause were a movement of the sea 

 floor ; hence a preference for this ' hypo- 

 thesis of Straljo ' hardly seems warranted. 

 The submergence of our southern coast may 

 now be going on, while the northern coast 

 may be at present rising, but not risen 

 enough to correct an earlier and greater sub- 

 mergence. This would make diverse conti- 

 nental movements the essential cause, and 

 displacement of the sea floor onlj- secondarj-. 



GEOLOGIC ATLAS OF THE CXITED !<TATES. 



Although primarily of geological inter- 

 est, the sevei'al folios of this great atlas now 

 issued are important to geogi-aphers fi-om 

 the accurate and succinct accounts that they 

 give of topographical features. The topo- 

 grapliical sheets alone are verj' instructive ; 

 but their value is greatly increased when 



