180 SEWER DESIGN 



parallel lines. The article referred to gives the diagram with 

 tabulated values of x and y, and of the relation of Vi/S to g, 

 or the grade per hundred. Several numerical examples are also 

 given. 



But even this graphical determination of v is not enough. 

 In sewer-design, except at the limits, the value of v is useful 

 only as it enters into the value of Q. A diagram, then, to be 

 thoroughly useful should give at once the value of Q from 

 the physical data, viz., slope and size of pipe, and the next 

 chapter is devoted to the construction and use of such dia- 

 grams. It remains in connection with Kutter's formula to 

 mention the set of tables which, except in the form of a graph- 

 ical diagram, give the formula most conveniently for use. 

 Reference is made to Flynn's tables, published as Nos. 67 and 

 84 o f Van Nostrand's Science Series. These are made possible 

 in their form by establishing the fact that, within the ordi- 

 nary limits of use for pipes, sewers, and conduits, the value 

 of s affects the value of c almost not at all, and therefore s may 

 be taken as constant, c then varies only with R and n. Tables 

 are calculated for any one value of n, values of c being 

 given for values of R. Instead of tabulating the values of c, 

 however, it is noted that the equivalent of_(), viz.^cVR-S 

 can be broken up into the two factors Ac\/R and Vo, and the 

 value of v can be taken as the product of c\/R and \fs. 



Further, since for pipes flowing full the value of R is pro- 

 portional to the diameter of the pipe, diameters are written 

 instead of values of R; the tables then give (for a certain value 

 of n) diameters of pipes from 5 inches up to 20 feet, and for 

 those diameters the corresponding values of A, of R, of c\/R, 

 and of Ac V^R. 



For any slope, its square_ root, given in another table, 

 multiplied by c \^R or A - c\/R for the desired diameter gives 

 the resulting velocity or discharge. 



No. 67 gives tables for circular sewers from 5 inches to 

 20 feet in diameter with ^ = .015; tables for egg-shaped sewers 

 (old form) i'Xi'6" to 12' Xi8/ flowing full, two-thirds full, 



