74 



SEWER DESIGN 

 TABLE DC 



Then assuming that the hard earth yields 20 per cent of the 

 rain, and reducing from Table VIII, we get finally the amount 

 of water discharged from a given rain in terms of the varying 

 densities, as follows: 



TABLE X 



By plotting the final percentages as ordinates with the 

 corresponding densities as abscissae, a curve may be drawn 

 which will express the relation between these two variables 

 (see Fig. 14). The equation of this curve may also be found 

 if desired. 



A small amount of additional data may be added as corrob- 

 oration to the results of Mr. Kuichling. In Ithaca, 1910, the 

 two seniors already referred to carefully measured the various 

 surfaces in a district of 42 acres that had a normal population 

 of 22 per acre, with a house on every lot but one, with results 

 given in the following table : 



