DAVIS. — ROCKY MOUNTAIN TERTIARIES. 365 



probability that its strata have been deposited for tlie most part by 

 aggrading rivers. The sediments to-day laid down by the Theiss and 

 other rivers that wander over the central parts of the plain are of very 

 fine texture. Borings show that similar sediments underlie the surface 

 to depths of 100 to 200 meters. As described by Penck, these deposits 

 consist of a complex of fine sand and clay layers whose sections, dis- 

 closed in neiglil)oring bore holes, are so unlike that deposition in a lake 

 is held to be impossible. The plain of the middle Rhine is a longitudi- 

 nal graben, enclosed by uplands through which the river has cut its 

 narrow gorsje north of Bingen ; but here again the evidence of borings is 

 taken by Penck to be decidedly in favor of a fluviatile origin for the 

 deposits (Morph. der Erdoberfl., ii, 15). In both cases it must be con- 

 cluded tliat the deformation by which the basins were produced was so 

 slow that the production of lakes was prevented by deposition on the 

 depressed floor and by erosion on the rising rim. An older example of 

 this kind is offered by the fresh-water Molasse of Switzerland, flanking 

 the Alps on the north, and now uplifted, tilted, and eroded. It is often 

 referred to as a lacustrine formation, and its marls may well justify such 

 a reference ; but its heavy sandstones and conglomerates, such as are 

 now upturned in the marginal range of which the Righi is a member, 

 give strong suggestion of fluviatile origin. The resemblance of the Swiss 

 Molasse to the Siwalik beds of northern India has been pointed out by 

 Medlicott (Quart. Journ. Geol. Soc, 1868, 45, 46). 



The subrecent deposits of Kashmir, Nepal, and Hundes, all basins 

 within the Himalayas, are of special interest in the present connection, 

 for they have been described as lake deposits, although now referred 

 chiefly to fluviatile agencies (Manual Geol. of India, 2nd edition, 422). 

 Their dimensions are comparable to those of some of our western Ter- 

 tiary basins. They frequently contain fine deposits in the more central 

 areas, and these may have been laid down in temporary lakes; but in 

 Kashmir the repeated occurrence of beds of shingle and sand alternating 

 with thin layers of lignite point to a subaerial origin ; and while the 

 central deposits of Ilundes are " a fine homogeneous clay with but little 

 gravel in it, . . . there is nothing to show that the whole [series of layers] 

 . . . might not be of subaerial origin, as it is almost certain that the 

 bulk of them might have been." The clays and gravels now dissected to 

 a depth of 3,000 feet contain mammalian remains, including the rhi- 

 noceros, ox, horse, hyena, sheep, and goat. 



13. Rocky Mountain Basin Deposits. — The resemblance is so 

 strong between several of the basin deposits here described and the Ter- 



