APPENDIX D. GEOLOGY. 169 



the base of the bluffs to the river the country presented a gradual slope 

 of four hundred feet. 



Section No. 10 is intended to represent the geological formation from 

 the river level to the summit of the bluffs ; the inferior strata, or those 

 between the base of the bluffs and the river, having been ascertained, 

 from numerous observations, to consist of gypsum and red clay. From 

 the drift I obtained specimens of chalcedony, jasper, granite, and ob- 

 sidian. 



July 4. — The formation as observed to-day consisted of red clay, 

 gypsum, and drift : they were all found occupying the same relative 

 positions as before. Soil mostly fertile ; subsoil argillaceous. 



July 5. — Observed in the prairie a circular outcrop of finely lami- 

 nated calcareous sandstone about three hundred feet in diameter, and 

 presenting a quaquaversal dip of forty degrees. Over the prairie were 

 strewn a number of small boulders variously composed of mica-schist, 

 greenstone, and quartz. Red clay, gypsum, and drift, the same as before. 

 Soil and subsoil arenaceous. 



July 6. — Observed a number of hills, varying in height from fifty to 

 one hundred feet ; in form they resemble truncated cones, and were 

 composed of horizontal layers of sandstone and red clay. General 

 formation the same as before. Soil in some places fertile; subsoil 

 argillaceous. 



July 1. — With the exception of the drift, which appears to be rapidly 

 diminishing in thickness, the formation did not differ from that pre- 

 viously observed. The surface was everywhere whitened with beds of 

 gypsum and loose fragments of carbonate of lime. The former varied 

 in thickness from five to fifteen feet ; in it were observed large quantities 

 of selenite. 



July 8. — The formation was mostly composed of red clay, with a 

 few local deposites of soft carbonate of lime and dark-colored cellular 

 sandstone. Saw no drift or gypsum to-day. Soil fertile; subsoil 

 argillaceous. 



July 9. — Again came in sight of the Witchita mountains: the one 

 nearest to us presented the form of a truncated cone, with an irregular 

 basin-shaped depression upon the summit. The formation everywhere 

 consisted of red clay; in a few places it was overlaid by thin seams of 

 gypsum, containing selenite. I observed a number of local deposites of 

 white carbonate of lime. Like the gypsum, it was found overlying 

 the red clay. On our route we passed four conical hills, from fifty to 

 seventy feet high, and composed of- red clay, interstratified with dark- 



