112 



TRANSPORTATION OP DEBRIS BY RUNNING WATER. 

 TABLE 16. Values of j lt in Ccfih, the coefficient c,, being a constant Continued. 



The greatest contrast between the rates of 

 variation of the two exponents is found when 

 relations to slope are considered, the least 

 when relations to fineness are considered. 



The variations of the two exponents with 

 respect to slope are illustrated by figure 35. In 

 the example from which the curves in this 

 figure were computed the range of variation, 

 within the experimental limits, is considerably 

 above the average, but the example is otherwise 

 typical. The rate of change is everywhere 

 smaller for j 1 than for i,, and the total change, 

 or range of variation, is therefore smaller. This 

 relation prevails throughout the range of slopes 

 covered by the experiments but would not be 



found to hold for slopes far outside of that 

 range. The average range of j lt for the investi- 

 gated cases, falls between one-half and one- 

 third of the average range of i t . 



It thus appears that a modification of the 

 plan of formulation which dispenses with varia- 

 tion in the coefficient and thereby concentrates 

 all expression of variation in the other param- 

 eter, the exponent, tends also to diminish di- 

 versity in that parameter. 



EFFECT OF CHANGING THE UNIT OF SLOPE. 



The values of j l are functions not only of the 

 conditions of experimentation and of the con- 

 stant slope a but also of the unit used for the 



