EAST AND WEST BIJOU HILL 483 



the basin. In the vicinity of Virgin Buttes boulders are found rising to 

 the level of about 2,200 feet. On the north slope, south of the Moreau 

 Eiver, evidence of a similar altitude is found by the occurrence of similar 

 northern boulders capping Patched Skin Buttes. What seems incon- 

 sistent is the fact that south of the Patched Skin Buttes no drift boulders 

 are found over a considerable area of less altitude. The extent, also, of 

 this driftless area on the south is surprising in its narrowness and the fact 

 that it is more than 100 feet lower than the Patched Skin Buttes. 



But the flat-topped, rick-like buttes, apparently marking an old shore- 

 line, were not all covered with boulders and much of the old shoreline was 

 not marked by these buttes, but, on the contrary, the surface was gently 

 undulating, very similar to glaciated surface. Such a case was noticed 

 6 or 7 miles east of Timber Lake. Approaching it from the west, no 

 boulders were found until coming into this gently undulating topography 

 and overlooking an apparent depression on the east, where boulders were 

 plentiful and the surface had a very close resemblance to till topography. 

 Here, again, there were traces of erosion which had carried the boulders 

 toward the adjacent watercourses. Fortunately, there had been recent 

 grading of an automobile road, which exposed a section from the surface 

 down two or three feet and for many rods in extent. From these expo- 

 sures it showed very clearly that the boulders were scattered on a surface 

 of residuary clay or of Pierre or Laramie clay, but very certainly not any 

 glacial till. Moreover, upon the elevations the boulders were not more 

 than half submerged in the soil, while in depressions the boulders were in 

 some cases completely covered with soil. The elevation of the top of the 

 boulder-capped buttes and of the moraine-like surface seem to be at the 

 same level. The boulder-capped buttes lie west of La Plant, extending 

 several miles. The upper limit of the moraine-like surfaces at other 

 points did not rise above 2,155 feet. 



Outlets. — Another evidence of the former existence of Lake Arikaree 

 is the finding of outlets. We have already spoken of the driftless char- 

 acter of the surface lying west and south of this lake and of the abrupt 

 appearance of numerous boulders when a certain level was reached which 

 might be supposed to be the boundary of the lake, the margin or water 

 level. Around the Che3^enne Indian Agency near Forest City the surface 

 northward is without boulders as soon as the level of the highest river 

 terrace has been passed. The surface is very much eroded and composed 

 largely of Pierre shale. About 10 miles west of Cheyenne Agency one 

 suddenly comes upon the valley of Stone Creek, which is named from the 

 abundance of northern boulders found in the valley. The bottom of the 

 valley is not very clearly the course of a stream, for erosion has chano:ed 



