Processes in the Use/id Arts. 151 



ways of making such compensations : for the sake of illustration, suppose 

 the following : The proprietors agree that such reservoir may be made, 

 providing that only the surplus water of floods be detained therein, and 

 that all the rest shall be allowed to flow down the rivulet as formerly ; 

 that is, all the water necessary for such proprietors, shall be allowed to 

 flow down the rivulet whilst it produces that quantity, and when it does 

 not produce that quantity, they are to have all that it does produce, the 

 same as if no such reservoir were there. 



The usual way of accomplishing this, is to cut an aqueduct round one 

 side of the reservoir, along which the water of the rivulet is always car- 

 ried past the reservoir, except during floods, when the surplus water is al- 

 lowed to flow over into it. A little consideration will show that a very 

 great quantity of water is thus lost. In the first place, the proprietors 

 below must have all they require, before any is allowed to flow over into 

 the reservoir ; but the rise of water in the rivulet that sends a part over 

 into the reservoir, must also send more down the aqueduct; this addi- 

 tional quantity sent clown is therefore lost. But, in all such situations, 

 there must be other small streams falling into the rivulet, between the re- 

 servoir and works below ; and the same rains that swell the rivulet above 

 the reservoir, will also swell the streams below it ; and, consequently, the 

 whole additional water yielded by these streams is also lost.* As the 

 quantity of water thus wasted, is generally much greater than that detain- 

 ed in the reservoir, and as the apparatus about to be described saves 

 the whole, its importance may be easily conceived. 



But, besides this, the proprietors on the rivulet below generally stipu- 

 late to have a certain supply of water from the reservoir during the dry 

 season, as a bonus for allowing the reservoir to be made ; and, as the re- 

 gulating of this supply has heretofore been left to watermen, who, inde- 

 pendent of neglect, caprice, or ignorance, are liable to be biassed by vari- 

 ous considerations which are well known to have frequently occasioned 

 vexatious disputes and litigation between the parties concerned, it becomes 

 extremely desirable to be independent of such agents. The apparatus 

 shown in Plate VI, Fig. 10. (given in Last Number) by regulating such 



• To explain this more fully, let ABZ, Plate I, Fig. 24, represent the course of the 

 rivulet upon which the reservoir CD E is to be formed ; AFB the aqueduct to carry the 

 usual water of the rivulet past the reservoir ; Z the mill or other work on the rivulet be- 

 low the reservoir, which requires the greatest quantity of water ; (and, of course, when 

 it is supplied, all the others must be so,) G, H, I, K, streams that fall into the rivu- 

 let between the reservoir and mill Z ; L a part of the bank of the aqueduct, low- 

 er than the rest, over which the surplus water of floods passes into the reservoir, 

 and which is made of such height, that no water can pass over into the reservoir un- 

 til enough passes to supply the mill Z. But, when the water rises above this, and 

 a part flows over into the reservoir, an additional quantity must also pass down the 

 aqueduct, which is therefore lost, the mill Z having enough before. Again, the 

 same rains that swell the rivulet above the reservoir, will also swell the streams G, 

 H, I, K, below it; all this additional water 6ent down by them is therefore also 

 lost, 



