Mr. Thorn on New Self-acting Sluices. 101 



E, the self-acting sluice that opens and shuts that aperture. 



FG, a lever which turns upon the fulcrum H, and is con- 

 nected at one end with sluice E, and at the other with the 

 float BD. 



The sluice E is here represented open, (as when the mills 

 are going,) but when the water is stopped at the mills, it 

 rises in the aqueduct, and with it the float BD, which raises the 

 end G and lowers the end F of the lever FG, and shuts the 

 sluice E. When the water is again let upon the wheel at 

 the mills, the surface of the aqueduct falls, and with it the 

 float, which opens the sluice E a,s before. 



Upon the lever FG, there is another small lever KL, which 

 turns upon the fulcrum L, and has a weight M suspended to 

 the other end K. In the ordinary working of the apparatus 

 this lever is quite stationary, and produces no effect whatever ; 

 but during floods the aqueduct is swelled by streams that 

 run into it between the reservoir and the mills, and when 

 this happens when the mills are not at work, the water, rising 

 in the aqueduct, presses up the float upon one end of the 

 lever when the other can get no farther down, and would 

 thereby strain or break the apparatus ; but by this contriv- 

 ance this extra pressure merely pushes up the small lever 

 KL without straining any other part. Of course, the weight 

 M is so adjusted, that the lever KL will not at any time move 

 till the sluice is shut, but upon the least extra pressure after 

 it shuts, the lever will rise. 



The dimensions of the float are nineteen feet square by 

 seven inches deep ; the lever is twenty- seven feet long, being 

 twice the length between the fulcrum and the sluice, that it 

 is between the fulcrum and the float. The sluice is three 

 feet three inches long, and fifteen inches deep. 



To determine the proper dimensions of the float, and rela- 

 tive lengths of the ends of the lever, it was necessary to as- 

 certain how far the sluice required to be raised to pass the 

 quantity of water wanted, and also how far the water in the 

 aqueduct might be raised above the level absolutely necessary 

 for supplying the works; the first was found to be seven 

 inches, and the last only four inches. The end of the lever 

 connected with the float was made therefore only half the 

 length of the end connected with the sluice ; and the float 



