102 Mr. Thorn on New Self-acting Sluices. 



was made of such dimensions, that when sunk half an inch 

 in water, the weight of water thereby displaced was equal 

 to twice the weight required to shut the sluice.* When, 

 therefore, the water in the aqueduct rises upon the float half 

 an inch, (besides what it sinks by its own weight,) the sluice 

 begins to move ; and by the time the water rises other three 

 inches and a half, the sluice is of course seven inches down, 

 or shut. 



This apparatus was erected at Rothesay in 1816. 



The Waster Sluice, Plate II. Figure 7. 



This sluice, when placed upon any river, canal, reservoir, 

 or collection of water, prevents the water within the embank- 

 ment from rising above the height we choose to assign to it ; 

 for whenever it rises to that height the sluice opens and passes 

 the extra water ; and whenever that extra M*ater is passed, it 

 shuts again ; so that whilst it saves the banks at all times 

 from damage by overflow, it never wastes any water we wish 

 to retain. 



ACBL is part of a canal, river, stream, or collection of wa- 

 ter. 



BC, high-water-mark, or the greatest height to which the 

 water is to be allowed to rise. 



BD, a sluice, or folding dam, which turns on pivots at D. 

 EF, a hollow cylinder, having a small aperture in its bot- 

 tom, to which is joined, 



EL, a small pipe always open. 



IIII, small holes in the cylinder EF, on the line of high- 

 water-mark. 



GH, another cylinder, water proof, that moves up and 



* Twice the weight, because here the lever is two to one against the float. 

 To ascertain the power required to open or shut the sluice, (which is easily 

 done by a lever and weights,) it must be tried when the water in the reser- 

 voir is at the highest, which, in this case, is seven feet above the bottom of the 

 sluice. To ascertain how far the sluice must be raised to pass the necessary 

 supply, it must be tried when the water in the reservoir is nearly at the low- 

 est, and in this instance was done when it stood three feet above the bottom 

 of the sluice. The quantity of water required is equal to about the power of 

 fifty horses, the fall at the wheel being twenty feet. The aqueduct is about 

 seven hundred yards long, twelve feet wide, three deep, and its bottom about 

 twelve inches lower than the bottom of the sluice. 



