26 
MEASUREMENT AND DIVISION OF WATER. 
to determine the form and conditions of a weir such that no 
single cause would produce more than one half of one 
per cent, error between the actual discharge and that 
given by the formula. 
His investigations were based principally upon the 
experiments of Francis, supplemented in certain direc¬ 
tions by some of his own. 
His work is interesting and valuable, from the 
thorough study he has given to the various disturbing 
causes, and the means of lessening their effect. 
Fig. 7.—the villoresi or cippoletti trapezoidal module. 
The dimensions are given in decimals, with the length of the sill as the unit. 
The effective length of the rectangular weir, as already 
noted, becomes less as the depth of water becomes greater. 
Also, the effective length of two weirs is not in the ratio 
of their lengths. These facts form objections to the 
rectangular weir. 
