MARCOU CREEK.—OAK CREEK.—BUFFALO GRASS. 27 
September 2—Camp 33.—Travelled about four miles and arrived at Marcou creek, where was 
a geological outcrop, which, contrary to expectation, proved to be gypsum. Five miles beyond 
"we came to Wood creek, a similar stream, the crossing of which was attended with much 
trouble. Elms, cotton-wood, and oaks were growing near. Continuing two and a half miles 
over the prairie, we struck a stream with flowing water, and a fine wooded valley. Having 
ascended its oak-lined banks four miles, we encamped upon the west side. Burnt prairies now 
surround us, accounting for the bright fires seen lately at night. This is probably the work of 
Indians to prepare fresh grass for the herds of buffalo that will be slaughtered on their return 
from the north. Two carcasses of these animals were seen to-day, and the rich grama which 
bears the name of ‘‘ buffalo-grass’’ also made its appearance for the first time. The water of 
Oak creek is but slightly brackish, though the banks are full of efflorescent salts of sulphate of 
magnesia. 
