3 ^ 
one-liH^fc!^ the angle, ^ the acceleration of gravitation and h the 
value 0.62, which is about the average 
value for^fcL^^^ an orifice, and ^ its value, the formula becomes 
P =2.65 TtJ 
n the discharge in cubic feet per second, 
and h is measurediiBi^^^^* right angle notches it is then 
5 
= 2.65 h^. 
EXPLANATI< 
OF TABLES. 
Tables I and II in the appendix are 
the errors due to velocities in the approach! 
eolations indicated 
Table I. is an auxiliary table giving the av 
for different velocities over the weir. It may be u 
the water as it approaches the weir, under known co 
second table, to determine the proper conditions of th 
to bring the errors within assigned limits. The vel 
velocity in the plane of the weir. If, then, the cross-sec 
the weir is no larger than the weir itself, the^yelocity of the 
would be the same as that of the table. 
r the purpose of correcting to allow for 
water without the troublesome cal 
fage velocity through the weir 
id to determine the velocity of 
ditions, or with the aid of the 
size of the channel, in order 
city given is fhe average 
jon of the channel above 
ater through the section 
If the section is t^E^ice that of the weir, 
3, and expresses the 
To use, the dis- 
ection is applied 
roach. The cor- 
iments limited to 
that the quan- 
[he water passing 
with velocity of 
ihe number 14.3 
e the dis- 
^sponding 
odified 
then the velocity is one-half that of the table. 
Table II is computed from the Fteley formula on page 
increase due to velocity over that given in the tables III-V 
charge as given in tables III-VI is determined, and the cor 
according to the given depth over the weir and the velocity of a 
rection is expressed in percent. The formula is based on expe 
2.5 feet per second. For greater velocities, therefore, it is possibl 
titles given are in error. 
Example. —What correction to allow for the velocity of 2 feet per second, 
over weir 1 foot deep. Find at top the column with depth 1 foot, and at left find lin 
2 feet per second. Follow the line to the right and in the column with depth 1 foot 
is found which is the number of per cent, by which the discharge is increased. 
Tables III and IV are newly computed for this edition, and gi 
charges over weirs with the depths measured in inches and fractions corr 
to the divisions on the rules ordinarily in use. They are computed from 
forms of the Francis formula, the depths being measured in inches. 
8 
Table III is computed from the formula, Q=.006675 LH 2^ Q being in c 
feet per second, L and H in inches. L ... 
Table IV is computed from Q = .080107 LH 2 , where Q is in cubic feet pei 
second, L is in feet, H is in inches. It is the Francis formula with the units changed. 
Tables V and VI were given in previous editions, but the depths being given 
in decimals of feet were not so convenient for use with scales which most people 
possessed which are divided into feet, inches and fractions. 
In table III the discharge is given for a weir one inch long, forming a por¬ 
tion of a longer weir, and for all depths up to 30 inches, the depths varying by six¬ 
teenths of inches. The even inches are given in the left hand column and fractions 
at the top of the page. The discharge for the corresponding inch and fraction is 
found at the intersection of the line of the even inch and the column of the fraction. 
Where there are contractions, the amounts to be subtracted are given in the second 
column. These are given for intervals of half inches, the quantities there given 
being for the even inch or half inch of the adjoining column, and for two complete 
contractions. 
Example. —What is the discharge over a weir 45 inches long and with a depth of 1114 inches 
with two complete contractions? . , , , i . v 
Find 11 inches at the left of the page, and the column headed 14 ,inch at the head of the page. 
Follow this column down until it intersects the line of the 11. At the intersection is the discharge, 
for a portion of the weir 1 inch long, which is .2519 cubic feet per Second., Then for a weir 45 inches 
long it is 4.5 times as much, or 11.334.5 second feet, if without contraction. The second column gives 
