The Meridian times. (Meridian, Idaho) 1909-1938, 1912-03-08

a Fiye-eighths miners inch per
acre for 100 days equals 24S feet
deep on the land.
s. Five-eightbs miners inch per
acre for 100 days equals 3.72 feet
deep on the land.
Q. One-half miners inch per acre
for 100 days equals 1913 feet deep on
the land
TO- One.half miners inch per acre
for $50 days equals 2.9S feet deep on
the land
Welrs and Weir Measurements.
The most accurate, practical and
economical method OF water meas
urement that has been devised for
the measurement OF comparatively
small heads OF water Ia the weir
measurement. The weir consists es'
sentially Of q thin notch OF specific
shape, which the water Is caused TO
flow over. The amount OF flow de-
Ponds upon the depth of water flow.
ng over the crest, as the bottom of
the notch Is called. The weir has
been used for the measurement OF
water for hundreds OF years and the
method OF It's installation and the
discharge OF water can be measured
over II with an error of less than one
per cent, IL care Is used.
There are several forms OF weirs.
the name OF each designat-
ing the shape OF the notch Cippo-
lett, an Italian engineer, evolved
and perfected the weir which bears
HIS name, many years ago, this be-
ing the weir that Is now most gener-
ally used In the west.
Weir Box.--In order to maintain
the weir In a proper and constant
position .and to prevent leakage
around and under II, and In order
that all water that Is to be measured
should be conducted over II, 1t Is
usually necessary to construct some,
sort OF box or frame to hold the
weir In plpce. A common form or
type OF this box which Is recon-
mended for one foot Cippoletti
weir is nine feet long. two and a half
feet deep and three feet wide inside
measurement, and with a one foot
weir will measure with accuracy.
amounts ranging from ten to fifty
Idaho miners inches.
Where a weir box is built, 1t Is nee
essary that II be made of sufficient
size and depth In comparison to the
size OF the weir notch to eliminate
all excess velocity Of approach. If
the box Is built too narrow or too
shallow Ii will add to the velocity of
approach to such an extent that cor
rect measurement can not be Sc
cured. 1t Is but a mere matter OF
convenience, however, to have a box
of the exact length prescribed, for
that part of the box above the weir
may be omitted IL settling basin or
pool OF the same size Is constructed
in the ditch above the weir. The
weir boxes and pools which should
be constructed for weirs of larger
sizes should be in the same proper
ton with respect to the size of the
weir as for the one foot, The size
OF weir box that Is required in order
TO eliminate velocity of approach has
been found. by experiment, to be APP
proxlmately seven times the cross
section of the weir notch.
Discharge. The discharge of weirs
has been accurately calculated by
various engineers who have carried
on hundreds OF experiments, cover
luk AtdIb vi anu ~ 10 Aouhu
that under like conditions the same
depth always produces the same dis
charge over the same size of a weir.
The conditions given for the con-
structlon and installation OF weirs
must be rigidly adhered to, however,
If accurate measurement Is to be
made. The formula which has been
evolved and which gives the dis
charge of accurately constructed
Cippoletti weirs is
@ equals 1857 l. II 80.
Where @ equals the number of Gu.
bic feet per second, l. equals the
length OF crest In feet and II equals
the depth of water on the crest in
feet, provided the same Is measured
from a point level with the crest and
up stream from 1t at distance equal
to the length OF the crest
/. The weir box should be set with
It's floor even with the bottom Of the
ditch and should be level in all dlrec
lions. The weir itself should be ex
actly level and perpendicular.
2. The channel leading to the weiI
should be of uniform cross section, OF
what Is still better, should gradually
enlarge as the weir Ia approached
The axis of the stream should pass
through the weir and perpendicular
to it: or, In other words, the well
should be located ut right angles Il
the middle of the stream. The ad
vancing stream should he free from
internal cross currents or eddies, al
these have an influence upon the dis
charge,
! 3. The water should be brought ~
nearly as possible to state Of res
+ before II enters the weir. An excess
velocity OF approach due to the We
loeity OF the advancing current will at
feet Uncreasel the discharge mor'
than almost any other one thing
This velocity can he reduced by wild
ening and deepening the box or poo
above the weir. 1t Is calculated tina
weirs three feet long with a depth o
water of twelve inches, should no
have a greater velocity OF approach
than six inches per second, whicl
amount may be allowed to increas
very slightly where greater depth
over wider weirs are used. BY cor
Istrueting the box or pool above tn
weir with a cross section at leas