96 SEWER DESIGN 



Chief Engineer of the Metropolitan Water-supply made to the 

 State Board of Health of Massachusetts in 1895, and is described 

 as follows (see Fig. 19). First, ignoring the city limits and 

 taking the metropolitan area within 10 to 15 miles radius 

 from the centre of business, the U. S. Census for Boston was 

 found to give 269,754 population in 1850, gradually increasing 

 to 844,814 in 1890. Then, by using partial and incomplete 

 censuses, such as assessed polls, names in directory, enumera- 

 tion of school-children, and making a compilation of other 

 statistics which indicate, to some extent, the growth of com- 

 munities, such as the number of buildings erected and the 

 number of water services added, and comparing these quantities 

 with the known population in census years, it was possible to 

 obtain the population of the district for the years 1891-1894 

 with much greater accuracy than could have been done by 

 projecting ahead the previous rate of growth. In this way the 

 probable population for 1894 was found to be 967,000. On 

 the diagram given, which is taken from the report mentioned, 

 are plotted population curves of Boston and five other cities, 

 with five-year spaces for abscissae and population for ordinates, 

 and all the curves are so placed as to coincide at a point cor- 

 responding to a population of 967,0x30 on each. Philadelphia 

 and Chicago are of little value in showing the tendency of the 

 curve, but London, Berlin, and New York show the rate of 

 growth of those cities beyond the point where they had Boston's 

 population, and by assuming that Boston's future growth would 

 be influenced by no tremendous shock of pestilence, war, or 

 business disaster its population line was drawn to follow approx- 

 imately these other cities. 



The check which the 1910 census has given to this work 

 shows it to have been surprisingly accurate. Thus in 1910, 

 sixteen years after the diagram was made, the census showed 

 a population in this district of 1,520,470, while the diagram 

 gives 1,500,000. 



The same method was followed in the smaller city of Brock- 

 ton, as found in the Report of the Sewerage Commission of 1893 



