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SEWERAGE OF COUNTRY TOWNS. 141 
the conduits is‘the first:point. House drains of four inches deliver 
into laterals (or branch sewers) of six inches, and these are con- 
tinued until the accumulated flow causes them to run half full. 
Then, and not until then, they are enlarged and are continued as 
before until the accumulated flow causes them to run half full ; 
and so forth, until the outfall sewer of the system or of the section 
is reached. The calculations are very close. They can be made 
so with perfect safety as regards chance of surcharge because the 
flow is known and is constant, and because no down-comers deliver 
a mixture of air and water into them during rain. The second 
point, and a fundamental one too, is the placing of automatic 
flush-tanks at the head of each sewer-line, by means of which a 
live or scouring stream of pure water is secured once or twice or 
three times in the day; and you will observe that the requirement 
is for automatic tanks, and that hand-flushing is quite a different 
thing. The third point is the use of glazed e. w. p. throughout 
the system, and a fourth is the making of the joints both absolutely 
smooth inside and absolutely watertight. Then a fifth point 
is the possibility of getting rid of a proportion of expensive man- 
holes, for which in many places a simple arrangement of glazed 
piping can be substituted ; and so also are lamp holes got rid of 
too—for on the one hand the pleasure of being able to see through 
a pipe sewer is but small, I should imagine; while on the other 
the right-line plan of Jaying obliges corners to be turned upon 
curves of very short radius. Then a sixth point is the laying in 
the same trench with the sewer of a line of drain tiles wherever 
these may be necessary, the discharge from them being to the 
surface. Lastly, the seventh point is abolition of the disconnector 
trap; but I do not say more about that because it is debateable 
whether anything is gained or whether something is not lost by 
getting rid of it, and that question need not be entered into now. 
Those are the essential or characteristic points; but as e. w. p. 
can be economically used, I believe, up to a diameter of eighteen 
inches, I add that so great a diameter could seldom be necessary 
in such towns as I now contemplate. I will just mention a practical 
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