92 THE JOURNAL OF GEOLOGY. 



but are unable to ascend across the flood plain to the Mississippi ; 

 they therefore unite and form the Yazoo river which runs south- 

 ward along the eastern margin of the flood plain, near the foot 

 of the bluffs. It would have to pursue an independent course all 

 the way to the Gulf, were it not that the Mississippi comes 

 swinging across the plain, and picks up the Yazoo at Vicksburg. 

 But it is the topographical sheets of the U. S. Geological 

 Survey that afford the greatest variety of illustrative material 

 for this country ; and it is not too much to say that the facts 

 they present create a revolution in the student's knowledge of 

 his home geography. We may well wish that they were more 

 'accurate, but, with all their imperfections, they present a great 

 body of new information. Under the family of plains there are 

 examples of low litoral plains in New Jersey and Florida, the 

 latter being so young that the constructional lakes are not yet 

 drained. The moderate advance in denudation of an upland — 

 itself an old lowland of denudation — is seen in the meandering 

 gorge of the Osage in central Missouri ; the relatively uncut 

 plateaus of Arizona are seen alongside of the beginning of their 

 denudation in the grand canyon of the Colorado. Maturely dis- 

 sected plateaus are found in West Virginia and eastern Kentucky ; 

 in northern Alabama and northern Arkansas ; but the first two are 

 of minute topographic texture ; the second two are of coarser 

 forms. Outliers of past-mature plateaus are shown on several 

 sheets in central Texas. All manner of other illustrations are 

 found in the same series of maps. The thoroughly adjusted 

 streams of the Pennsylvania Appalachians ; the superimposed 

 streams of northern New Jersey ; the Illinois river, the type of a 

 medium-sized river in the abandoned channel of a large river ; 

 this being the only well-mapped example of the kind in this 

 country ; the warped intermontane valleys of Montana ; Crater 

 Lake in northern California ; glacial lakes in Massachusetts ; 

 flood plains slanting away from their river in Louisiana ; fiords 

 in Connecticut ; moraines in Rhode Island ; drumlins in Wiscon- 

 sin ; trap ridges in New Jersey ; revived old mountains in North 

 Carolina ; half-buried mountains in Utah and Nevada. Every 



