268 



Proceedings of the Royal Physical Society. 



of denudation ; but it by no means follows that Playfair, or, 

 indeed, all who have just been cited, view^ed river-terracing 

 as impossible apart from successive elevations of the sea- 

 board. 



Hitchcock, in America, seems to have been among the first, 

 after Playfair, to recognise that rivers, with sufficient power 

 of flow, will make terraces even if left to themselves.* The 

 interior terraces of the Connecticut, he says, are not best 

 explained by successive elevations of the land, -f In subse- 

 quent writings he distinguishes two classes of river terraces ; 

 — those cut from level to level as the ocean by stages retired, 

 and those due to a natural tendency of rivers to terrace their 

 banks. In his " Illustrations of Surface Geology," however, 

 he complicates his earlier statement by an unfortunate " ideal 

 section" representing each terrace as built up separately 



Fig. 3. 



Ideal Section of a Terraced Valley (Hitchcock, Geol. of Vermont, 1861, 

 vol. i., p. 96). 



1, Alluvial Meadow, with E, river ; 2 and 3, River Terraces of coarser 

 materials ; 4, "Moraine Terrace," or highest level-topped terrace, containing 

 ice-dropped materials. This terrace has subsequently become irregular 

 through the melting of ice ; 5, probable Sea- Terrace or Beach ; 6, Glacial 

 Drift resting upon rock. 



from the bottom of the valley. % There is much, however, 

 that is of great value. The river terraces are distinguished 

 both from lake terraces and maritime teiraces. They slope 

 with the valley. Their number and height are often diff'erent 



* Geology of Massachusetts, 1833, p. 136. t Ihid., Edition of 1841. 



X Illustrations of Surface Geology, 1857. I have not seen this work, but 

 the same views of river action and the same diagram are given by C. Hitchcock 

 in " Geology of Vermont, 1861," pp. 94-190. 



