172 APPENDIX D. GEOLOGY. 



July 24. — The sandstone appears to be gradually becoming more 

 abundant, while the red clay is less frequently observed than before. 

 Saw no gypsum to-day. Soil fertile, and in some places six feet deep ; 

 subsoil composed of yellow clay. 



July 25. — Passed a number of small conical hills composed of red 

 clay, overlaid by sandstone. The latter was highly ferruginous, and 

 contained nodular concretions of iron. Soil and subsoil the same as 

 on yesterday. 



July 26. — Formation the same as before. 



July 27. — At about eight o'clock we came to an extensive outcrop 

 of bluish-gray, non-fossiliferous limestone, which presented in many 

 places a highly crystalline structure. Its relative position was found to 

 be below that of the sandstone. Passed a number of hills, varying in 

 height from one to two hundred feet, and composed of limestone, over- 

 laid by finely laminated sandstone. Soil fertile ; subsoil the same as 

 before. 



July 28. — To-day the sandstone disappeared almost entirely, its place 

 being occupied by limestone of nearly the same character as that en- 

 countered yesterday. Soil and subsoil the same as before. 



July 29. — Remained in camp. 



July 30. — To-day we again observed the limestone in great abund- 

 ance. It presented nothing different in character from that previously 

 described. The sandstone and red clay were also in many places largely 

 developed. Soil very fertile; subsoil the same as before. Started from 

 camp at four o'clock in the afternoon. For the first few miles we found 

 the sandstone largely developed ; after passing which, we came to an 

 outcrop of limestone of the same character as that previously noticed. It 

 presented itself even with the surface at an angle of thirty degrees, and 

 was over a mile wide. Immediately beyond this we came to a deposite 

 of coarse granite of a reddish color, and variously traversed by veins of 

 quartz. This remarkable formation (as I have been informed) extends 

 about twenty-six miles in an easterly and westerly direction, and is 

 nearly six miles broad. Throughout its entire extent it is said to present 

 the same character, and is everywhere surrounded by aqueous strata. I 

 observed to-day in one of the creeks several boulders, composed of 

 milky quartz ; the largest was four feet in diameter. Soil and subsoil 

 the same as before described. 



July 31. — Shortly after starting this morning we again struck the 

 limestone formation, which continued to be largely developed during 

 the remainder of the distance to Fort Washita. In it I observed a large 

 number of the characteristic fossils of the cretaceous period. 



