and complaint. Finally the magistrates of Milan attempted 
to regulate matters, and called for plans of modules, ‘and 
gave twelve conditions which a module should satisfy * 
It was in response to this proposal of the Milan rulers 
that boldati proposed the module which was adopted and is 
still in use on the canals of that province. 
CtanOtxT 
Figure 2. 
The first thing Soldati considered important was to in¬ 
sure that the water should flow with uniform pressure. This 
he attempted to do by the following principle; 
If two chambers are connected, as in the diagram, the 
water in the second chamber will be lower than that in the 
irst by an amount depending on the relative size of the ori- 
c f. s * .pu t ^ e pths the two chambers are in a constant 
ratio. 1 hus, if the depth in B is 6 inches, and in A 18 inches, 
it the water in A becomes twice as deep, that in B will also 
ecome twice as deep as before. Under these circumstances, 
f/ 1 . iacre ase in depth of 18 inches in A causes an increase one- 
By means of such a regulating chamber, therefore, the 
variations in the height of the water in the canal are lessened 
in the regulating chamber, which is intended to furnish the 
water under constant pressure. While apparently avoiding 
e ifhculty caused by a varying head, this really does not do 
so. As a matter of fact the flow zvill increase in the same ratio 
Jor a given increase in depth of the main channel, whether the 
orifice comes direct from the main channel or from the regulating 
chamber , provided it be at the same level. 
. T he reason for this fact, which is contrary to general 
opinion of those using water from the ditches under such 
systems, is this : As the velocity of water flowing from an 
1 V M. ries ™ w ^^ the square root of the depth, according to 
the familiar Torricellian principle, the discharge for an open- 
mg of constant size will vary with the square root of the 
del IrX h a e 7,v!np 0 rlpi °m t i hiB e — 1 the is & iven in Bruschetti’s “Storia 
tTefvTnondr BUff0n ' S “, D ? S Canaux /irrigation d’llaHe kp^ntrS.” Th e 
tMeWe conditions are incluaed in the unmarked conditions on page 14 It is also 
Idrometrif” “ bmiths “ Italian Irrigation;” in “ Parrochetti’s Mmiuale Pratico di 
