STORAGE AND REGULATION OF WATER. LV. 



through a small hole, so that the effect of the shock is lost 

 and the gate comes to rest quickly. 



An altogether new style of movable weir, and the best 

 in use at the preseut time, was introduced in 1852 by M. 

 Chanoine. This gate consists of a shutter turning on a 

 horizontal axis, forming the top of a trestle, which is 

 hinged to the floor; a strut hinged to the same axis supports 

 the gate when raised. The bottom of this strut rests in a 

 cast iron shoe out of which it can be pulled, when it is 

 necessary to lower the gate horizontally on the floor. A 

 weir of this description has been in use for some years 

 across the Darling river at Bourke, where however the 

 cumbersome "tripping bar" by means of which in the 

 French weirs, the strut was pulled out of the shoe is 

 replaced by a simple device, by means of which the raising 

 and the lowering of the shutters are both effected in a very 

 simple manner. When a shutter is to be raised it is pulled 

 forward till the strut falls into the shoe, and if it is to be 

 lowered the gate is pulled a little more forward, dragging 

 the end of the strut up an inclined plane which is cut away 

 at an angle of 45° in plan, so that when the strut falls over 

 its top it has nothing to support it and so slides down a 

 guide with the shutter folding over it. 



One great defect in the action of these weirs is that 

 often when the shutters have tipped over, they will not right 

 themselves till the water level has fallen very much, and 

 so reduced the storage capacity by a large extent. In 

 the case of partly fixed weirs, this difficulty was overcome 

 by M. Chaubart when he designed his self regulating gate. 

 This gate, instead of turning on a trunnion joint, is supported 

 by a pair of sectors which roll on horizontal planes, chains 

 or links being used to keep them in position. As the 

 shutter becomes more and more inclined so does the point 

 of support move proportionally upward, so that it is always 

 in equilibrium. 



