July 18, 1884.] 



SCIENCE. 



63 



orate its life. However this may be, there 

 can be no doubt, that, this stage of pupilage 

 passed, it was well that a new and larger field 

 was opened here on this continent, where its 

 activity might be more productive, and its 

 growth more steady. On the North-American 

 continent, and especially in the United States, 

 it would seem that each separate geological 

 problem is stated in the clearest way. In stra- 

 tigraphy, where shall we find a series so con- 

 tinuous and complete as in the region of the 

 Wahsatch Mountains? In mountain structure, 

 where are the extreme types so perfectly ex- 

 pressed as in the Appalachian on the one hand, 

 and the basin ranges on the other? In land- 

 sculpture, where are there examples so simple 

 and grand as in the plateau region ? Of the 

 obscure phenomena of the glacial epoch, where 

 may we hope to find an explanation, if not in 

 eastern United States ? In the still more ob- 

 scure problems of chemical geology, such as 

 the geneses of ore-deposits, — problems which 

 have hitherto baffled the utmost efforts of sci- 

 ence, — what field so promising as the Ameri- 

 can Cordilleras, where the process is still going 

 on under our ejes ? Finally, in paleontology, 

 where are there fields richer than the paleozoic 

 basin of the east, and the wonderful cretaceous 

 and tertiary deposits of the west ? 



These reflections have been suggested by 

 reading the two bulky volumes before us. 

 There can be no doubt that the establishment 

 of the U. S. geological survey is an epoch not 

 only in the geology of this country, but in the 

 science of geology itself. Excellent work has 

 been done before by individual effort, by state 

 surveys, and b}^ surveys undertaken by the war 

 and interior departments ; but never before has 

 the work been organized in a manner befitting 

 so noble a field. The volumes before us are a 

 proof of the excellence of the work being done : 

 they consist of full abstracts of a series of 

 monographs, most of which are }-et unpub- 

 lished. A simple enumeration of these is suffi- 

 cient to show their great importance. The} T are 

 Dutton's ' Physical history of the Grand Canon 

 district,' Gilbert's ' History of Lake Bonne- 

 ville,' Russell's ' History of Lake Lahontan,' 

 Hague's ' Geology of Eureka district,' Em- 

 mons's ' Geology of Leadville district,' Beck- 

 er's ' Geology of Comstock lode,' Irving's 

 ' Copper-bearing rocks of Lake Superior,' and 

 Chamberlin's ' Terminal moraine of the sec- 

 ond glacial epoch.' It is evident that only 

 the most rapid review of these memoirs is pos- 

 sible here. 



The geology of the plateau region, through 

 the labors of Powell and Dutton, is so well 



known that only a brief recapitulation of its 

 wonderful history is necessary. This region, 

 now the highest in general elevation of the 

 continent, was a sea-bottom, continuously or 

 nearly so, from early carboniferous to the end 

 of the cretaceous, and received, during this 

 time, conformable sediments twelve thousand 

 to fifteen thousand feet thick : this indicates, 

 of course, a subsidence to the same extent. 

 At the end of the cretaceous it began to rise, 

 passing successively through brackish-water, 

 fresh-water, land, and high-plateau conditions 

 to the present time, the extreme elevation be- 

 ing not less than eighteen thousand to twenty 

 thousand feet. Accompanying this elevation, 

 and as its effect, there has been a general ero- 

 sion by which from six thousand to eleven 

 thousand feet thickness of strata have been 

 removed over the whole area, leaving the pla- 

 teau still from seven thousand to eight thou- 

 sand feet high ; and lastly, into this plateau, 

 a canon-cutting from three thousand to six 

 thousand feet deep. The general erosion has 

 given rise to a series of cliffs from a thou- 

 sand to two thousand feet high, and extending 

 for hundreds of miles ; while the elevation, 

 especially in its later stages, has broken the 

 earth-crust into parallel oblong blocks from 

 twenty to thirty miles wide and a hundred 

 or more miles long, which, by settling un- 

 equally, have produced vertical displacements 

 of a thousand to six thousand feet. These 

 displacements, having occurred in compara- 

 tively recent times, have not yet been obliter- 

 ated by erosion, and therefore still exist as 

 cliffs. Thus, besides the east and west ero- 

 sion-cliffs, there are also north and south 

 displacement-cliffs : these latter pass by in- 

 sensible gradations into monoclinal bends of 

 the strata. As soon as the region became 

 land, of course a river- system was estab- 

 lished. As the region rose, the rivers cut 

 down pari passu, and thus maintained their 

 positions. The Grand Canon itself, into 

 which the tributaries drain, is in the axis 

 of the elevation. Thus it has come to pass 

 that the rivers run against the inclination 

 of the strata, cutting deeper as the strata 

 rise, southward. This remarkable persistence 

 of river-beds, in spite of great orographic 

 changes, was first pointed out by Powell. 



The time when these different events oc- 

 curred has been accurately determined by 

 Dutton. In eocene times, nearly the whole 

 plateau region was covered by the waters of a 

 vast lake, in which many thousand feet of strata 

 were deposited, — the same which yielded such 

 treasures of mammalian remains to Marsh and 



