io The: Colorado Experiment Station. 
the United States, the quantity taken by the ditch, and therefore 
by the laterals, is constantly varying. In most cases a user is 
entitled to a certain fraction (depending upon his number of shares 
of the capital stock) of the whole amount of water. Most contracts 
reduce to such a statement in the last analysis. If there be 600 
shares outstanding, then omitting the more complicated cases which, 
however, are the common ones, each share is entitled to 1-600 of 
the available supply. Hence in nearly every case the problem be¬ 
comes essentially one of equal division, complicated by various 
other conditions. There are few cases in which the consumer can 
demand a constant flow of a definite quantity. This requirement is 
not necessary and is rarely desirable. In most canals, where there 
are a large number of users, the simplest way of giving each per¬ 
son his share is to measure out a definite quantity. The manager 
or ditch rider determines how much water is available, after allow¬ 
ing for the loss by seepage and evaporation which experience has 
shown for that particular ditch. Perhaps he may be limited by 
the amount in the stream and this may be fluctuating. Then 
knowing from the reports of the ditch riders how many shares will 
call for water, he divides the available amount of water by the num¬ 
ber of shares so calling, and thus determines how much is available 
for each share. The object is, then, to measure to each his propor¬ 
tional amount. Like the depositors in a bank, it is rarely that 
all users call for water at the same time. If the supply of water 
for the canal is constant and the demand is constant, then the flow 
to which each share is entitled is constant. Practically, however, 
this is never the case; hence, it is more important that the boxes 
be capable of exact measurement and of adjustment than it is 
that they give a constant flow. The fluctuating conditions are met 
by setting the boxes or adjusting the gates once or twice per day 
or oftener in strenuous times. At best this is an approximation. 
I am inclined to think that with the development of a practicable 
register of low cost, less attention will be given to the daily ad¬ 
justment. This is already done in the case of reservoir water. 
The class of measuring boxes adapted for measurement has 
been called by the Italians, “Modulo.” It is more convenient in its 
French form, “Module,” and this name therefore, is used to 
designate those boxes whose object is to measure the quantity of 
water delivered, or to give a constant flow. The word, “Divisor” 
will be restricted to the class of boxes, previously referred to, whose 
only object is to divide water. 
There will always be cases where the Divisors are the most 
convenient, especially in the small ditches. In all other cases 
modules of one kind or another will be found to be the better. 
The problem is to determine the one best adapted to the special 
