154 



gilbert: transportation of debris 



very consistent set of observations which together with the calcu- 

 lated angles and new elements are shown below. 



HODGKINSONITE 



po = 0.7201 go = 1.1025 /i=84°35' a:6:c = 1.538: 1: 1.1075 ^ = 84^35' 



GEOLOGY. — The transportation of debris by running water. ^ 

 G. K. Gilbert, based on experiments made with the assist- 

 ance of Edward Charles Murphy. 



Scope. The finer debris transported by a stream is borne in 

 suspension. The coarser is swept along the channel bed. The 

 suspended load is readily sampled and estimated, and much is 

 known as to its quantity. The bed load is inaccessible and we 

 are without definite information as to its amount. The primary 

 purpose of the investigation was to learn the laws which control 

 the movement of bed load, and especially to determine how the 

 quantity of load is related to the stream's slope and discharge 

 and to the degree of comminution of the debris. 



Method. To this end a laboratory was equipped at Berkeley, 

 Cal., and experiments were performed in which each of the three 

 conditions mentioned was separately varied and the resulting 

 variations of load were observed and measured. Sand and 

 gravel were sorted by sieves into grades of uniform size. Deter- 

 minate discharges were used. In each experiment a specific 



^ Abstract of U. S. Geological Survey Professional Paper 86. (In press.) 



