April 19, 1895.] 



SCIENCE. 



441 



own: so little advance has yet been made 

 towards a general concensus of opinion in 

 this new subject, the rational study of the 

 forms of the land. 



In its fundamental princijiles the classi- 

 fication of features proposed by Major 

 Powell will endure, for it is based on struc- 

 ture and process, not on external form 

 alone. In some other respects it does not 

 seem acceptable, for there is a certain in- 

 consistency and incompleteness in its ter- 

 minology that is disturbing. For example, 

 diastrophism having been defined in the 

 first monogi'aph as meaning upheaval or 

 subsidence, with or without faiilting or 

 flexure, and gradation having been defined 

 as including all processes of disintegration^ 

 transportation and deposition, we read in 

 the second monograjjh that diastrophic 

 mountains and diastrophic hills result es- 

 sentially from the action of gradational pro- 

 cesses on uplifted masses ; but that dias- 

 trophic valleys, diastrophic cliifs, diastrophic 

 cataracts and diastrophic islands result 

 from movement alone without degradation; 

 and no place is given to mountains of es- 

 sentially constructional form, corresponding 

 in origin to the diastrophic valleys and cliffs. 



Valleys of gradation, cliffs of gradation 

 and gradational cataracts result from pro- 

 cesses of degradation ; yet it must of course 

 be understood that the land masses acted 

 on by gradational processes had in these 

 cases, as well as in the case of diastrophic 

 mountains or hills, in some way gained an 

 efl'ective height above baselevel ; hence it 

 would be more consistent to call most 

 mountains and hills • gradational;' and thus 

 reserve the adjective ' diastrophic ' for 

 mountains and hills made by diastrophism, 

 like diastrophic valleys and diastrophic clifl's. 

 Gradational islands are deposits of land 

 waste near shore, and gradational hills are 

 heaps of debris left directly or indirectly by 

 glaciers; while sand dunes are given an 

 efjuivalent value with gradational hills, in- 



stead of being placed with glacial hills 

 under a general gradational heading. 



Sea plains are plains of ultimate denuda- 

 tion with reference to the sea as the con- 

 trolling baselevel; the sea plain may be 

 enlarged by sedimentation along its margin, 

 but no mention is made of the numerous 

 plains resulting from the uplift of smooth 

 sea-bottoms. Lake plains are formed with 

 their baselevel depending on the level of 

 lakes; lake-bottom plains, revealed by the 

 deepening of the lake outlet (" the waters 

 of the lake rush through the newly opened 

 channel, and the lake is di-ained in whole 

 or in part," is an unfortunate suggestion of 

 a sudden change that must be very rare in 

 nature), are included, but without special 

 name, under the same heading with plains 

 produced bj- denudation of the surrounding 

 land down to lake level: and without any 

 indication that the latter are rare and the 

 former common. 



The gradual change of opinion regarding 

 the comparative efiicacy of marine and 

 subjerial erosion gives some justification of 

 the small share of space devoted to the pro- 

 cesses of the seashore: but it is to be re- 

 gretted that they are so disproportionately 

 condensed. After nearly two pages about 

 inland clifts of gi-adation, sea clifls are dis- 

 missed with less than two lines of text: 

 " On sea coasts and lake shores, sapping is 

 canned on by the waves, and cliffs are often 

 produced." Floods are rather fully treated 

 and flood plains are given about two pages, 

 but deltas are dismissed with the briefest 

 mention. Coast-foi'ms in the second essay 

 have less than two pages of the total thirtj'. 

 The explicit omission of seashore features, 

 or their postponement to a later monogi-aph, 

 would have been pi-eferable to so brief a 

 treatment. 



Those who have enjoyed ^Major Powell's 

 eloquent accounts of his western explora- 

 tions will be glad to see again here some- 

 thing of the fervor of his style; but in a 



