rate of the flow of approximately 405 gallons per hour, or
about 9,700 gallons per day. When the flow is about lin deep
the same variation of 1-16th in will represent about 162
gallons per hour, or 3,900 gallons per day. Greater accuracy
will be obtained if a properly-formed gauging pond is
constructed independently of the manhole and a double
rectangular notch, similar to Fig. 13, or a triangular or V-
shaped notch, as shown in Fig. 14, used in lieu of the simpler
form.

In calculating the discharge of weirs there are several formula
to choose from, all of which will give different results,
though comparative accuracy has been claimed for each. Taking
first a single rectangular notch and reducing the formulae to
the common form:

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Discharge per foot in width of weir = C \/ H^3

where H = depth from the surface of still water above the weir to the level of
the bottom of the notch, the value of C will be as set out in the following
table:--

TABLE No. 5.

RECTANGULAR NOTCHES.
_____
Discharge per foot in width of notch = C \/ H^3
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Values of C.