82 SEWER DESIGN 



flow in pipes in order to secure a satisfactory capacity for all 

 sizes. 



Taking the formula as deduced above, 



3Q.27/ 5 1542.*' 



he changed the exponent of D from 5 to 6 in order to get a larger 

 value for the amount of run-off. 



Then substituting ^- for Q, on the assumption that ^ of 



a precipitation of r, =i inch per hour, will reach the sewer 

 during this period of time, he has 



6168.5' \6i68.5' 



Ar 



For any other value of r than unity, - - would have to be 



2 



substituted for Q, giving 



6168.5 

 But for the flow in the conduit, as above, 



D=f-; 



\I542.S' 



and equating the two values of D, 



Biirkli-Ziegler published in 1880 a paper on the discharge 

 of sewers,* and in it proposed a variation of Hawksley's for- 



* Introduced into this country in 1881 by Rudolph Hering in his classic report 

 to the National Board of Health. 



