150 



UNIVERSITY OF VIRGINIA PUBLICATIONS 



Hydrographic Survey recognized this by actually gauging tiie velocity 

 of flow directly in a given cross-section. The Table V consists of 1,085 

 experiments with the authority from which each is taken. Under the head 

 of 1000 s is entered the observed hydraulic slope, under the heads of Y, r, 

 100 »io and (?„ are entered the observed velocity, hydraulic mean radius, 

 observed value of m and corresponding observed coefficient of velocity C 

 respectively. Under 100 m and C are entered the computed values of m and 

 C from the formula (44), in wliich the values of the coefficients /i and A are 

 given for the twenty different classes at the head of each class into which the 

 channels of flow have been divided. Some two hundred other observations 

 on natural rivers whose regimen was more irregnilar were studied with the 

 conclusion reached above, and consequently they were not tabulated. N"ot 

 because the coefficients of roughness were not found among the classes in the 

 table, but because the laws of flow were so irregular as not to admit of suffici- 

 ently precise computation. For the same reason the class of pipes known as 

 old, foul, tuberculated and incrusted pipes have been omitted. First because 

 their imposed obstacles are such as to give no definiteness to their degrees 

 of rouglmess; second because the irregularity and distribution of the in- 

 terior projections was such that their surfaces, as those of irregular natural 

 rivers, no longer constitute a homogenous heterogeneity of surface that 

 could be defined or relegated to a definite classification, and consequently 

 the disturbances of stream lines, cross currents and eccentric eddies are 

 such as no longer obey the laws which govern a regular, systematic and 

 symmetrical disturbance. 



TABLE V. 



Class 1. 



fj. = .010, A = .000090. 



