590 



TRANSACTIONS OF THE AMERICAN INSTITUTE. 



It might be presumed that a study of the natural conditions of drainage, 

 and an inquiry as to the large surcharge of water in sewage flow, wouLd 

 have led to the adoption of a more delicate and elaborate system for the 

 several subdivided districts of drainage than massive and costly arterial 

 sewers, and that the tubular or venous system would have been ingrafted 

 on, the arterial as a matter of simple induction. But, jn drainage as in 

 water supply, designors and constructors have been proved to copy the 

 examples immediately before them, without due examination of their in- 

 herent defects in principle and failures in practice; or have lacked the 

 courage to attempt changes which seemed experimental. The analogy 

 between water flow into a city and sewage flow out of it has therefore been 

 practically disregarded, and cities like London, whicl^ considered four feet 

 water mains enormous in caliber, yet constructed Fleet sewers 18.5 feet by 

 12, to assist in the ordinary discharge, and classified sewers 5 feet by 2.5 

 as " small sewers" for subordinate districts. The city of New York, with 

 about 200 miles of six-inch water pipes, builds no sewer less than 48 by 32 

 inches; and Paris, which doles out its house to house water supply by 

 hand, builds the sewers from 4.16 by 6.25 feet to 13.41 by 15.41 feet. It 

 is a singular fact in the history of modern engineering, that London is now 

 expending near £6,000,000 in building intercepting sewers, designed to 

 carry not less than twice the ordinary flow of the Thames River, and the 

 city of Paris is following her example. 



From an entire misapprehension of the fluidity of sewage flow and the 

 causes of clogged and surcharged sewers, the order of nature has been 

 generally reversed, in our modern cities, and the arteries have been built 

 where the veins would have answered a much better purpose. In all such 

 cases the results have amply condemned the practice, as to sanitary evils, 

 damages from floods, cost, and expense of administration. 



The capacity of comparatively small tubes, for drainage, is fully illus- 

 trated in the following table of areas of discharge, sizes, and inclinations, 

 calculated for a storm-fall of two inches per hour, including house sewage 

 and street wash: 



Area in acres drained under a storm/all of tioo inches per hour. 



By this table it appears that under the most excessive storm-fall on 

 record, supposing it to discharge continuously, a twelve-inch pipe will free 

 a street 972 feet long and 60 feet wide, draining house-lots 100 feet deep 

 on each side, with the moderate grade of one in sixty. 



While the arrangement of the main arteries is controlled by the aggre- 

 gate supplies they are to receive, and sewers of but five feet diameter will 

 drain 1,000 to 1,500 acres, the arrangement of the lateral connections should 

 be controlled by the nature of their special action. Here, where water 



