100 



SEWER DESIGN 



of the city increases, which law, as shown in the report, holds 

 if cities of from 160,000 to 900,000 be included in the com- 

 parison. As a check on the law and for comparison, the author 

 has taken the Census report for 1910 and computed the rates 

 of increase in a similar manner for cities of between 10,000 

 and 200,000, with results as shown in Table XIII and in Fig. 22. 



TABLE XI 



TABLE SHOWING RATES OF INCREASE IN POPULATION FOR CITIES 

 OF DIFFERENT SIZES 



In this latter comparison the law seems to be lost, the increase 

 in the annual rate depending apparently not so much on the 

 size of the city as on other unknown factors. In both diagrams, 

 populations are plotted as abscissae, and the average annual 

 rate of increase in per cent as ordinates. The broken irregular 

 line shown is obtained by joining the points thus plotted, and 

 if a continuous regular curve be drawn between the points, 

 as nearly as may be, it will represent the probable general law 



