J. L. Rich — Large Bowlders in Gravel Deposits. 441 



Art. XXXYI. — The Occurrence of Unusually Large Bowl- 

 ders in Gravel Deposits ; by John L. Rich.* 



Various observers, particularly in western United States, 

 have described the occurrence of very large bowlders em- 

 bedded in the finer material of piedmont gravel deposits, 

 some of them in such situations that their transportation 



Fig. 1. 



Fig. 1. Block diagram illustrating general relations of various features 

 described. Dotted area is gravel. On the right is the eastern escarpment, 

 the nearest possible source for the large bowlders at X and Y. 



thither is difficult to explain. f In some cases the great size 

 of the bowlders and their situation with respect to their 

 nearest possible source is such as to render almost incredible 

 the idea of their having been transported by running water, in 

 spite of the well-known fact that the transporting power of 

 torrential streams is very great. In such cases the temptation 

 is sometimes strong to invoke the aid of glacial ice as the 

 only agent capable of having performed the task. 



* Published by permission of the Director of the U. S. Geological Survey. 

 + See references following; also Trowbridge, A. C, Jour. Geol., xix, 

 706-47, 1911. Capps and Leffingwell, Jour. Geol., xii, 702, 1904. 



