14 
MEASUREMENT AND DIVISION OF WATER. 
device adopted by them is therefore of some interest, irre¬ 
spective of the novelty of the plan. 
In their module the water enters a hollow vertical 
cylinder whose upper edge is kept at a constant distance 
below the surface of the water. The water then flows 
in with constant pressure. As the level of the water rises 
or falls the cylinder likewise rises or falls vertically, pass¬ 
ing through a water-tight packing. It would seem that 
the packing required to make the joint water-tight would 
interfere with its free movement up and down, and thus 
render the module insensitive. It seems to be used with 
satisfaction, however. The amount given to different users 
is regulated by the depth the cylinder is below the water. 
A simpler device for keeping the orifice a certain distance 
below r the surface was tried on the Montrose canal, in the 
western part of the State. The orifice rose or fell with the 
water of the canal, being supported by a float, and was 
connected with the lateral by a pipe and a flexible joint. 
The trouble in such an apparatus is to make a joint which 
shall be water-tight and at the same time flexible enough 
to be moved by a moderate-sized float when the water rises 
or falls. If this can be done it would satisfactorily solve 
the problem of giving a constant flow. 
On the Isabella I. canal, of Spain, another form of 
module has been proposed. Instead of having an orifice 
at a constant depth as on the Marseilles canal, the orifice 
varies in size as the head of water changes. With a small 
depth of water the orifice is large, with a large head it is 
small. The orifice is made larger or smaller by the water 
itself. In a circular hole in the bottom of the head of the 
lateral is a plug of iron, supported by a float. This is 
roughly conical in shape, with the largest diameter at the 
bottom. As the water rises in the canal the plug is lifted, 
partially stopping the orifice by the large diameter. As 
the water falls the orifice is opened. If the diameters of 
