946 



SCIENCE. 



[N. S. Vot. V. No. 129'. 



ward. The Tertiary, mostly composed of 

 sands and gravels, hundreds of feet in 

 thickness, derived from the Eocky moun- 

 tains, is explained chiefly as river wash, 

 and not as a lacustrine deposit. Its east- 

 ward margin is marked by an irregular es- 

 carpment formed on the ' mortar beds ' 

 (sand or gravel with calcareous cement). 

 Its general surface, away from the river 

 valleys, is broadly even. Faint depressions 

 or swales occur, holding water for a month 

 or so in the year ; they are ascribed to un- 

 equal settling of the strata, followed by un- 

 derground leaching. A further stage of 

 this process is seen in the ' arroyos,' slight 

 depressions of the surface with continuous 

 descent, like stream channels, but broad, 

 grassy and flat, with low bluff-like rims up 

 to their very heads. 



The uplands with their escarpments are 

 much dissected by the rivers, giving local 

 relief of 250 or 300 feet, and a greater 

 variety of scenery than is commonly asso- 

 ciated with the Great Plains ; yet it seems 

 something of an exaggeration to say of this 

 treeless region that " near any of the drain- 

 age streams one almost invariably finds a 

 varied and pleasing landscape which in 

 many respects is rarely surpassed in Amer- 

 ica." Even some of the larger rivers are 

 of inconstant flow ; for example, the Cim- 

 arron river ' has water in it throughout the 

 greater part of the year in most of its 

 course.' Bear and White Woman creeks, 

 one south, the other north of the Arkansas, 

 enter the State from Colorado in well-cut 

 valleys, and after heavy rains possess a 

 large volume of water with much sediment; 

 but their valley sides decrease in height 

 down stream, and at last the waters and 

 sediments are spread out on the even up- 

 lands or lost in the sand hills, without join- 

 ing any other river. Smoky Hill river is 

 working on bed rock for much of its course; 

 but the Arkansas has heavily aggraded its 

 valley. The report is illustrated with a 



number of photographs, whose value would 

 have been greater had they been taken 

 when possible from higher points of view. 

 The last of a number of plates gives a 

 bird's-eye view of the State, with geological 

 areas, rivers, and county boundaries marked 

 on the surface and vertical sections on the 

 margin, of much service in elucidating th& 

 text. 



BELL ON CANADIAN RIVEES. 



Robert Bell, of the Canadian Geolog- 

 ical Survey, discusses the ' Evidences of 

 northeasterly differential rising of the land 

 along Bell river ' (Bull. Geol. Soc. Amer., 

 VIII., 1897, 241-250), which flows north- 

 ward from the upper Ottawa to Hudson 

 Bay. Good proof is given that the upper 

 Ottawa crossed the present height of land 

 in postglacial time and followed the Bell j 

 and that its diversion to the St. Lawrence 

 is due to a rise of the land in the north or 

 northeast still in progress. Some of the 

 ragged expansions of the rivers, forming 

 lakes, which are commonly explained as 

 the result of drift barriers, are ascribed 

 by Bell to backwater flooding in conse- 

 quence of the tilting of the land. The 

 small relief of the region and the low 

 divides between the rivers, combined with 

 the resistant character of the ledges where 

 crossed by streams, are all favorable to 

 these results. The Bell river, flowing to- 

 wards Hudson Bay, has acquired a low- 

 grade course through a clay-covered low- 

 land of till ; it is here and there interrup- 

 ted by rapids on hard ledges. At present 

 the water becomes deeper (even thirty or 

 forty feet), the stream broader, and the 

 banks less defined in going up stream from 

 from one fall to the next ; and this is well 

 interpreted as a result of uplift in the 

 north. The out-branching ' lost channels ' 

 of various east- or west-flowing rivers are 

 generally found on the south side of the 

 main stream. The Churchill River seems 

 to be on the verge of spilling over south- 



