422 GEOLOGY OF THE DENVER BASIN. 



furnishing the bulk of the artesian supply of the field, thai is, the Laramie 

 and Arapahoe formations, the Denver formation being excluded from 

 consideration on account of the slight extent to which it enters into the 

 actual supply. The rainfall of the Denver Basin is therefore more than 

 adequate to the absorbing and transmitting power of the beds. The failure 

 of the wells to yield a larger supply is due to texture, by which these 

 properties are governed. 



THE WELLS. 



Tin- ,".!» I wells along the Platte Valley may conveniently he considered 

 in two divisions — one comprising those within Denver and its immediate 

 suburbs, 209 in number; the other, those iii the country, 185 in number. 

 Between the wells of the former division clearly developed relations exist, 

 relations that can not lie distinguished between the wells in the country or 

 between these and the city wells. The interrelation between the citj and 

 its suburban wells is attributable to their concentration within a limited 

 area which undergoes 'nit slight change in the geological conditions of its 

 strata; and the absence of such relations between the wells of the country 

 is due to their wide distribution and the ever-recurring, though slight, 

 changes in structural and stratigraphical conditions sure to exist over an 

 extended area. 



THE WELLS OF DENVEE ami its SUBURBS. 



In the following discussion the datum level to which depths of wells, 

 flows, and stratigraphical planes have been referred is the general level of 

 the Platte River at the font of Fifteenth street, Denver. Where departures 

 from this reference plane have been necessary they are specifically noted. 



In the consideration of the city wells the position of the strata under- 

 lying the area including them has been regarded as horizontal, which is, at 

 least, very near the actual case. There is, perhaps, a general dip of half 

 a degree to the northward, or down the Platte. Flexures, If present, are 

 insignificant. 



RANGl "I PLOWS IN STRATIGRAPH1C HORIZON. 



The thickness of the formations underlying the city of Denver and 

 involved in the artesian supply is about 1,500 feet, of which LOO feet may 

 be assigned to the Denver beds, 550 to 600 feet to the Arapahoe formation, 



