450 OSCAR H. HERS HEY 



50 feet deep. Thence extending a quarter of a mile down 

 stream, we find a strong moraine development, great piles of 

 huge granite bowlders rising from along the river to the foot of 

 the steep mountains, a quarter mile back from the stream. This 

 was evidently the work of the Cohnrad Gulch glacier, which 

 barely reached the north side of the valley and scarcely dammed 

 the river. It is a strand of this moraine system that rests on the 

 between 100 and 150 feet of stratified fine gravel and silt above 

 the Conzetti mine, as discussed in the paper before cited. From 

 the way the same moraine system comes down near the river 

 one-fourth of a mile farther up, there was apparently much ero- 

 sion between the deposition of the gravel and the glaciation of 

 its surface. This is a different conclusion than I have hereto- 

 fore expressed, as I maintained, in the paper referred to above, 

 that there was no dissection of the fine gravel deposit before the 

 formation of the overlying glacial moraine, but it now appears 

 that that statement was too hastily made. It now appears that 

 a deep, comparatively broad canyon was excavated by the river 

 into this gravel deposit, and subsequently when the Cohnrad 

 Gulch glacier reached the edge of this canyon it tumbled much of 

 its moraine material into it. The maximum extension of this 

 glacier certainly occurred later than the maximum extension of 

 the neighboring Brown's Gulch glacier, and there is evidence of 

 such a long interval between them as constrains me to refer the 

 former to the Wisconsin or last great stage of glaciation. This 

 conclusion is supported by Cariboo Creek having excavated jn 

 this glacial debris a much smaller trench than Brown's Creek 

 eroded in solid rock since the maximum extension of the Brown's 

 gulch glacier. Why these two neighboring glaciers should have 

 see-sawed in this manner is not clear, but from a neighboring 

 mountain I have seen that they headed in adjoining cirques which 

 seem to have been fed jointly by a higher cirque, and a careful 

 examination of the locality may furnish a satisfactory explanation. 

 Under the stratified gravel and silt just mentioned there is a 

 thin layer of fine gravelly blue clay, which rests on a bed of 

 coarse bowlders and ordinary river gravel. The blue gravelly 

 clay is very strongly contrasted with both the underlying and 



