CITY SANITATION AND SEWAGE DISPOSAL. 237 



the sewage in the tank rises to a height of 32 feet it would open the 

 check valve and allow the whole contents to rush out into the Lake. 

 As soon as the tank would be empty the valve would close again 

 and allow it to fill and again empty, etc., etc., "as long as grass 

 grows and water runs," according to the old adage. The time re- 

 quired for the tank to empty would be less than 7 minutes. The 

 time to fill would depend on the supply. If 4,000,000 gallons of 

 sewage were intercepted in 24 hours the tank would be filled eight 

 times or once in 3 hours. If less the time would be longer. 



Four flushes per day would be quite sufficient to keep the outlet 

 pipe free, as that is the object of the tank. The velocity of the outlet 

 pipe would be from 6 to 10 feet per second, and would carry along 

 bricks, stones, pieces of iron or lead. 



During the interval between the flushings the sewage from Front 

 Street East and West would keep up a constant flow through the 

 outlet pipe, only being checked by the closing of the valves when the 

 tank was in operation. 



This short cessation, instead of being a disadvantage to the system, 

 would be a decided advantage to it, as it would produce a slight ebb 

 and flow at each flushing of the tank, which would help to scour it 

 in its lower levels. The fall in Front Street from the bottom of 

 Garrison Creek sewer to the level of the water at Parliament Street, 

 a distance of 11,000 feet is 9.3 feet or 1 foot in 1,183 feet, a very 

 good fall and capable of giving a velocity of 4^ feet per second 

 flowing two-thirds full. Bufialo is projecting a sewer now with a fall 

 of only 1 foot in 4,650 feet. I am afraid they will have trouble there. 

 A reference to the map and drawings will help to make the above 

 description clear. 



The map shows probably the best location for the flushing tank. 

 It is provided with a ball and float as shown in Fig. I. This is not 

 an essential part of the system, as a syphon or any other device might 

 be used to open and shut the tank. 



Fig. II. shows the bed of the Don with outlet pipe sunk in the 

 angle formed by the bottom with the East bank. The intercepting 



