9 
ity is uniform across the whole cross-section, which is not the 
case, even in a uniform channel, and much less so in one ir¬ 
regular or in poor repair. Such a division is to the disadvan¬ 
tage of the smaller consumer. 
The nearer the velocity is uniform across the whole 
channel, the better this method of division, eviciently. Ac¬ 
cordingly means are frequently taken, by weir-boards or 
otherwise, with this object in view, but generally with indiff¬ 
erent success. A screen would accomplish this one object 
better, but the objections to its use are too many in most 
places to render it practicable. 
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• 
j 
1 
1 
1 
! 
Fig, 1.— A COMMON FORM OF DIVISOR. 
Figure i represents one of the most common forms of 
divisors. The partition board A is movable, and may be 
placed at different distances from the side C, so that the user 
can vary the proportion of water which he receives. A cleat 
of some kind is often used to prevent the board from being 
moved beyond a certain limit. Where the ditch is wide and 
shallow there is sometimes a simple truss used, as in the Lar¬ 
iat ditch, in the San Luis Valley, with a depending cleat. 
Sometimes a wire or chain restricts the movement. In these 
cases it is usually assumed that the amount of water going to 
the side channel is in proportion to the distance the movable 
partition is from the side, and the ratio is the same to the 
distance across as the volume is to the volume in the whole 
ditch. This is not in general true, because the velocity 
across the cross-section is not uniform. 
Sometimes where this is recognized, and it is necessary 
to make close division, the water is brought to a state of ap¬ 
proximate rest, or to a state of approximately equal velocity 
throughout the channel. In the case of some divisors used 
on the Farmers’ Union Ditch, in the San Luis Valley, a weir- 
board over which the water drops is placed above the division 
board. This secures an approximate equality. A fall below 
the point of division sufficient to prevent the backing up of 
the water is necessary. 
If water is brought to a complete state of rest, or very 
nearly so, and flows over the weir without lateral contraction, 
