278 WALLACE W. ATWOOD 



and a half miles down-stream, and perhaps much farther, but farther 

 out it would be difficult to distinguish it from the preglacial and post- 

 glacial alluvial deposits. 



Up-stream from the position of the terminal moraine, the drift 

 ridges, already mentioned, swing to appropriate positions for lateral 

 moraines and continue to the lower margin of the basin, as shown in 

 Fig. 1. The crests of these moraines are commonly but 40-50 feet 

 above the valley bottom, but they increase in elevation to the east- 

 ward, until at their down-stream termini they are at least 100 feet 

 high. The valley between the lateral moraines contains a drift- 

 filling which at places is more than 50 feet deep, and which may 

 perhaps be classed as ground moraine. In addition to the lateral 

 and ground moraines, there are medial moraines projecting down- 

 stream from the rock spurs which subdivide the basin. 



The topography and topographic relations of these deposits of 

 loose material are such that it would be extremely difficult, if indeed 

 possible, to account for their formation under any other hypothesis 

 than that of glaciation, but an examination of the material in these 

 deposits furnishes conclusive corroborative evidence of glaciation. 

 The material is entirely volcanic, but nevertheless has the character- 

 istic physical and lithological heterogeneity of glacial drift. Bowlders 

 up to 10 feet in diameter are found in the moraines, and in the exposed 

 sections there is every gradation down to the very fine material in 

 which the stones are imbedded. In all the exposures seen the drift 

 was unstratified. Many of the larger stones and bowlders are sub- 

 angular in form, with smooth and polished surfaces. In a region of 

 undoubted glaciation, such forms and surfaces would have been 

 accepted as positive evidence of ice-action, but in this region more 

 conclusive evidence was looked for, and in the fresher exposures, 

 especially in the debris from a 30-foot excavation in the bottom of 

 the valley, beautifully striated stones were found. 



The basin is not cirque-like in form, and probably it was not 

 greatly modified by the ice. It is subdivided at its head by projecting 

 rock spurs into four minor upper basins (1, 2, 3, 4, Fig. 1). Basins 

 1 and 2 have floors which are broader than would be expected if 

 developed by stream-erosion alone. On the floor of the basin num- 

 bered 1, a surface of bed-rock is exposed which has been polished and 



