Mesozoic and CcBnozoic Geology and Palceonfology. 313 



terrace of table land, the ancient shore of a great body of water, that 

 once filled the whole of the Red river valley. It is onl}' 210 feet above 

 the level of the surrounding prairie, or between 900 and 1,000 feet 

 above the ocean level. Higl> above Pembina mountain the steps and 

 plateaux of the Riding and Duck mountains arise in well defined suc- 

 cession. On the southern and southwestern slopes of these ranges the 

 terraces are distinctly defined, on the northeast and north sides the 

 Riding and Duck mountains present a precipitous escarpment which 

 is elevated fully 1,000 feet above Lake Winnipeg, or more than 1,600 

 feet above the sea. One of the terraces here is 1,428 feet above the 

 level of the ocean. The denudation of the Cretaceous, in the valley of 

 Lake Winnipeg, has been enormous, because the shales crop out 500 

 feet above Dauphin lake, where their position is nearly horizontal, and 

 evincing their former extension to the northeast, if not as far as the 

 north shore of Lake Winnipeg, Sand hills and rlunes occur on the 

 Assiniboine, Qu'Appelle, South Branch, and north of Touchwood hills. 

 Prof. E. W. Hilgardf described the drift (he called it the Orange 

 Sand formation) as covering the greater part of the State of Missis- 

 sippi. It is overlaid by the Bluff Group, and is not, therefore, 

 above Natchez, exposed oa the surface, within eight to twelve miles of 

 the Mississippi river ; below Natchez, however, it forms the White 

 cliffs on the Mississippi itself. It does not cover the northeastern 

 part of the State, and is absent from other limited patches. The 

 thickness is quite variable, sometimes reaching 200 feet, though 

 usually not more than 40 to 60 feet. The material is usually silicious 

 sand, colored more or less with hydrated pei'oxide of iron, or orange- 

 yellow ochre. Sometimes pebbles or shingle, either cemented into 

 puddingstone, or more frequently loose and commingled with sand or 

 clay occur, and at other times limited deposits of clay are found. It 

 contains fossils from the Silurian, Devonian, Carboniferous, and Cre- 

 taceous formations which are exposed to the north in Tennessee, Ken- 

 tucky, Indiana, Illinois and Ohio, and silicified wood from the lignite 

 strata of Mississippi. The character of the surface upon which it rests 

 its own irregular stratification, and the dependence, to a great extent, 

 of the nature of its materials, upon that of the underlying formations, 

 proves, bej'ond question, that its deposition, preceded and accompanied 

 b}' extensive denudations, has taken place in flowing water, the eflTect 

 of whose waves, eddies and counter curi-ents, is plainlj- recognizable in 

 numerous profiles. Nor can there be anj^ doubt that the general direc- 



* Geo. Sur. of Miss. 



