36 THE GEOLOGICAL STRUCT CEE, ETC. 



" mountains, quickly disappears in the loose gravels of the 

 " basin." * 



Many other similar instances may be quoted. The case of 

 the Llano Estacado, to which reference has already been made, 

 may be mentioned. 



The Llano Estacado is bisected Ijy the Canadian River, one 

 of the eastern tributaries of the Rio Grande ; the continuation 

 of this tableland northwards covers about 10 degrees of latitude 

 in the States of Kansas, Colorado, Nebraska, Wyoming, and 

 South Dakota. The western edge of this tableland is in places 

 over o, 000ft. in height, while the eastern edge does not reach 

 more than 2,000ft. It is drained by a far greater number of 

 streams than the portion to the south of the Canadian River. 

 This tableland is of importance in that it affords a means of 

 actually witnessing the escape of the water absorbed by the 

 strata on the higher ground to the west. 



" Many streams have a steadiness of volume, and that 

 " volume unaccountably large, if the rainfall of their several 

 " basins be regarded as the only source of supply, which indicates 

 " that they have eroded their channels down to the level of some 

 " sheet of water which feeds them with perennial springs and 

 " maintains a steady volume in spite of long continued drought. 

 " Take for example Frenchman River, the chief affluent of the 

 " Republican River. It has a catchment basin of about 700,000 

 ♦' acres, upon which 38,000,000,000 cubic feet of water falls 

 " each year. More than one-thu'd of this amount is delivered 

 " by the Frenchman to the Republican, and it flows on with 

 " very little change, month by month and year by year, without 

 " regard to variations in the ra^nfall. A smart shower may fall 

 " in that region without starting any surface flow upon the 

 " parched slopes and tablelands to swell the volume of the 

 " stream. In order to maintain so large and constant a volume, 

 " it must be fed from subterranean sources, and observation of its 

 " head waters discloses the actual existence of numerous and 

 *' strong springs of a perennial character."! 



* Drainage Systems of New Mexico ; R. S. Tarr, American Geologist. Vol. 5, 

 1890 ; pp. 269-270. 



; The Stratigraphy and Hydrology of Nebraska. L. E. Hicks. Preliminary 

 Report, Artesian Water investigation, west of the 97th meridian. Washington. By 

 authority : 1890, pp. 72-73. 



