20 COLORADO COLLEGE STUDIES. 



Milan base-line, the base, as reached by the drill, is appar- 

 ently some 300 feet lower than at Caldwell. Taking the 

 latter town as the base and Sharon or Attica as the approx- 

 imate summit of the Harper beds, and making no allowance 

 for dip, the difference of elevation of these places would 

 o-ive about 350 feet as the thickness of the Harper, a hgure 

 that would be reduced to about 250 feet, if the base as out- 

 cropping near Milan be taken as bench-mark. But that 

 dip or accession of sediments westward, or both, must be 

 reckoned with, is indicated by the fact that at Anthony, 

 which is at least 100 feet below the summit of the forma- 

 tion, (and where the Sumner division has at least its full 

 average thickness), the prospector's drill descended about 

 550 feet before reaching the apparent summit of the Well- 

 ington, making the thickness of the Harper, as thus meas- 

 ured, about 650 feet. 



Carbonate of copper, including both azurite and mala- 

 chite, occurs in the Harper formation, chiefly as stain in 

 calcareous shales in the basal part of the formation* (as at 

 Caldwell ) and more rarely in sandstone concretions at higher 

 horizons (as west of Harper) ; but the occurrences are lim- 

 ited and promise nothing of value from a mining point of 

 view. 



Some of the earthy brownish-red and gray shales of 

 the Harper formation, occurring a short distance east of 

 Kin^rman, form the basis of the "Cherokee Brown Mineral" 

 and "Silver Gray" manufactured by the Kingman Paint 

 Company, and which has had considerable demand in the 

 paint-trade of Topeka, Kansas City and other markets. 



THE SALT PLAIN MEASURES. 



Occupying an interval between the Harper and the 

 Cedar Hills sandstones, in southern Kansas and northern 

 Oklahoma, is a zone of red shales (? with some sand- 



*Really in transitional beds which might perhaps be reckoned 

 equally well as constituting the summit of the Wellington. 



