16 THE TONER LECTURES. 



to build others to supplement tliem. In this case it would be an 

 easy matter for all sewers lying above a certain level — all, in fact, 

 except those which drain the lower and flatter parts of the city — to 

 have their dry-weather flow intercepted, so that the ordinary foul 

 sewage may be led by gravitation directly to a suitable point for its 

 discharge. This may be done by building an intercepting sewer 

 adjusted in its size to this work only, at a level below the present 

 sewers at the points of interception, connecting the latter with the 

 intercepting sewer by such channels of communication as will 

 admit all of the foul sewage and the water used for flushing. 

 Channels large enough for this purpose would carry into an 

 intercepting sewer the flow of light rains. The waters of heavy 

 storms would pass on through the present extensions of the 

 sewers beyond the intercepting line, and find their outlet into 

 the B-street sewer or other large, outlet mains of the storm-water 

 system. Wherever it became necessary within this high district to 

 build independent smaller sewers for house drainage only, these 

 might be made to discharge directly into the intercepting sewer. 

 It is of but little importance that during heavy storms sewage 

 matter would be carried into and through the storm-water sewers, 

 for the reason that at such times the sewage is enormously diluted, 

 and is discharged into a torrent in the main sewers which is quite 

 sure to remove it inoffensively. At the termination of a storm the 

 flow of the laterals would be reduced to the capacity of the 

 intercepting inlets long before there would cease to be a considera- 

 ble flow in the storm-water sewers. 



For those parts of the city which lie too low for interception by 

 a sewer delivering above high water at a distant point, it would, 

 unquestionably, be cheaper and better to abandon all communica- 

 tion with the present large sewers, and to construct an entirely 

 independent system for house drainage, depending for this solely 

 on a pumping outlet, at least during the higher stages of the tide. 



I see no other way in which the drainage of this lower district 

 can be made satisfactory. For the carrying out of a plan requir- 



