28 The Colorado Experiment Station. 
very generally known in English speaking countries as the Cip- 
poletti weir. 
Cippoletti proposed to use a trapezoidal form with such angles 
that the increase in the flow caused by the triangular areas at the 
ends should balance the loss due to contraction. If this could be 
done, the correction for contraction is made automatically and the 
flow would be in proportion to the length of the sill. From the 
adopted coefficients of contraction it is found that this inclination 
would be practically one-fourth to one or three inches to one 
foot. This is not quite exact, but the difference is so small that it 
is convenient to use this for ordinary purposes. 
I made some experiments on weirs of this form, but of small 
size, before the first edition of this Bulletin. Other experiments 
were made by T. V. McVickers under the direction of Prof. Church 
The Cippoletti Trapezoidal Weir—Dimensions Based on Unit Length of 
Sill. 
of Cornell University. The most complete ones were made by 
Messrs. A. D. Flynn and Dyer of the Worcester Polytechnic School 
or Worcester, Massachusetts, who experimented with weirs from 
three to nine feet long and with depths of 18 inches. These indi¬ 
cated that the average error was above the one per cent, indicated by 
Cippoletti, but that the discharge is in proportion to the length of 
the weirs. This is the feature which makes this particular form of 
weir valuable for irrigation purposes. 
