TERRESTRIAL DEPOSITS OF OWENS VALLEY 741 



times. The surface on which the bowlders lie clearly was made by 

 running water. The bowlders are so clearly a part of the fans, 

 and the fans are so clearly running-water deposits, that the bowlders 

 must be considered to have been transported by running water. 



It is also clear that the bowlders were not transported according 

 to the common and well-known methods of stream transportation. 

 They have certainly not been rolled along the bottoms of streams in 

 the usual way. They have not the rounded form characteristic 

 of such motion. On the surface of the fans, furthermore, it is 

 impossible for streams to have existed deep enough and strong 

 enough to have so rolled these bowlders. Such streams would have 

 to have a depth about equal to the diameter of the bowlders, be 

 confined in a narrow channel, and flow with a velocity almost incon- 

 ceivable for a stream. As the bowlders occur on the higher parts 

 of the fans, water of sufficient depth to have carried them would 

 have formed a sheet 20 ft. deep over the fans, and 220 ft. deep over 

 the inter-fan depressions. Even then it would not have been con- 

 fined to a narrow channel. Also the gradient of the fans is rela- 

 tively low. Where the largest bowlders are, the slope is not over 

 6°, and west of Lone Pine not more than 3 . Bowlders much smaller 

 than these are not now being rolled down the mountain canyons 

 above, where the streams are sharply confined and the gradient is 

 very high. The volume of the stream may have been sufficient 

 to carry them in the canyons when the glaciers were there. The 

 problem involves transportation on the fans only. They were per- 

 haps carried to the heads of the fans by glaciers, glacial waters, and 

 gravity. From there to their present positions, some special 

 methods are called for. 



A clue to a possible manner of transportation for these bowlders 

 is obtained from observations of run-off water at the side of a pre- 

 viously dusty road after a heavy rain. Where the running water 

 is but a small fraction of an inch deep, pieces of rock an inch in 

 diameter are carried down stream. The moving of the large pieces 

 involves the transportation of a very much greater amount of fine 

 material. The movement of the large pieces is accomplished by the 

 removal of fine material from the area immediately down stream 

 from, and under, the lower part of the large piece. By undercut- 



