BY A. GIBB MAITLANI), C.E., F.G.S. 37 



A further instance may be mentioned in the Loup River 

 which lies to the north of those last quoted. The constant 

 volume of this river, in spite of drought or down-pouring rains, 

 neither of which cause a few inches less or more water, is easily 

 accounted for when it is kiiown that from Fullaton to Genoa 

 its channel is cut throngh the Llano Estacado beds down to the 

 impervious Cretaceous shales, and catches pretty well the whole 

 volume of water flownig through the Tertiary Beds. 



In some cases powerful artesian springs rise in the beds of 

 the rivers at places where erosion jnst reaches the top of the 

 water-bearing strata. Fine examples of this are seen in 

 Victoria Creek at New Helena, Custer County, and in the North 

 Loup River, where Big Spring rises in its channel. The 

 garrison at Fort Robinson, Dawes County, is supplied from 

 one of these springs which yields from 50,000 to 60,000 gallons 

 daily, or 18,250,000 gallons per annum. 



The leakage is not alone confined to the Tertiary Strata. 

 It has been shown that the water supply of the Dakota Sand- 

 stones is received along its outcrop at the foot of the Rocky 

 Mountains ; a portion of it may be derived from exposures to 

 the north of the United States frontier. There is evidence 

 pointing to the fact that there is a continuous discharge from 

 its eastern margin. 



Between the James River and the Sioux Falls the Colorado 

 Beds overlap the Dakota Sandstones, which do not reach the 

 surface in this locality. The wells of the James River Valley, 

 exhibit a much higher pressure and a greater discharge than 

 further to the south-east. The Dakota Sandstone is covered 

 with a variable thickness of glacial drift in the valleys of the 

 Missouri, the Big Sioux, the James, the Red and Vermillion 

 rivers, and the water from it escapes upward in the form of 

 powerful springs yielding saline and alkaline waters, almost 

 identical in composition with that drawn from the Dakota Sand- 

 stone of Jamestown. These artesian springs extend between 

 Chamberlain in the Missouri, and Sioux City, Iowa. This 

 leakage must be held accountable for the diminution in the 

 pressure of the wells in the south-east part of the basin, for 

 where strata carrying water are arranged in such a way 

 as to dip beneath the sea level, or the lower outcrop so covered 



