TWENTY-FIRST MEETING. 37 



I have a strong objection to all these schemes with regard to the 

 outlet pipes, being of the opinion that they would not operate satisfac- 

 torily, and also in case of the second and third schemes, with regard 

 to pumping, which is nothing moi-e nor less than a worthless, expen- 

 sive nuisance. The outlet pipes lie under water, so that they flow 

 always at the full, and knowing their size and the amount of sewage 

 discharged through them, it can easily be told to the thousandth part 

 of an inch what the velocity would be. I would call your attention 

 to the following table, and challenge anybody to refute its accuracy. 

 First through a seven-foot pipe : — • 



Feet 

 Gallons. per Sec. Miles jjer Hour, 



12,000,000 .577 .394 



9,000,000 .433 .295 



6,000,000 .288 .197 



12,000,000 6 ft. pp. -785 -534 



8,000,000 -523 '356 



4,000,000 .262 .178 



We know that 12,000,000 gallons is the average amount of water 

 that is pumped into the city per day, and allowing that it is all 

 returned to the sewers, by reference to the above table it would only 

 have a velocity of .577 ft. per second, less than seven inches, and in 

 the six-foot pipe of about 9^ inches. But we know that much of the 

 water pum]>ed into the city never reaches the sewers : for instance, 

 that which is used for watering lawns, sprinkling streets, building 

 purposes, steam engines, etc., so that a safer calculation would be to 

 take two-thirds or three-quarters of that amount. By reference to 

 the table you will see that 9,000,000 gallons will only have a velocity 

 of 5 1-5 inches per second, or less than 3-10 miles per hour. 



Mr. Baldwin Latham, one of the most eminent English engineers, 

 says in regard to self-cleansing sewers that, " In no case should the 

 velocity be less than two feet per second, but in the generality of 

 cases it should be much greater." Mr. N. Beardmore gives two and 

 a-half as the least, Mr. Phillips gives the same rate, while Mr. John 

 Neville says three feet per second is required. Now compare these 

 rates with the actual facts as set forth by the table — velocity required 

 two to three feet per second, actual velocity five to seven inches. We 

 are told in the reports of these experts that the velocity in some parts 

 of the system would be as high as five miles per hour, equal to 7J 



