Processes in the Useful Arts. 155 



EN, a small pipe communicating under ground, between EH, and 



N, a valve at the lower end of pipe EN, which, when open, is capable 

 of passing more water than the pipe HI can receive. 



R, a float, placed within a small pool of water, on the same level as, 

 and communicating with, the canal. 



The water in the canal is here represented at its greatest height, and the 

 valve N shut by the float R pressing up the spindle : the cylinder EH is 

 therefore filled by water from the cistern I, and the sluice B shut by the 

 pressure of the water in the reservoir, there being a little more pressure 

 below than above the pivots. When the surface of the water falls in the 

 canal, the float R falls with it, and then the valve N (falling by its own 

 weight) opens and empties the cylinder EH, when cylinder KL falls and 

 opens sluice B, and gives the supply required. 



It is therefore of no consequence in regard to regulating the supply of 

 water, how far the reservoir is from, or how high above, the level of the 

 works requiring the water ; provided that the length of the pipe EN cor- 

 responds with the distance, and its strength with the height or pressure of 

 the water. It is necessary, however, that the bore of this pipe should be 

 small, particularly where its length is considerable, in order that sluice B 

 may open or shut very soon after valve N opens or shuts, and at the same 

 time require only a small supply of water. Suppose, therefore, the open- 

 ing into the pipe EN at I to be only a half inch bore, and that the valve 

 N is shut when that pipe is empty, it is evident that the sluice B will not 

 shut, till both that pipe and cylinder EH be filled with water ; and that 

 the smaller the diameter of that pipe be, the sooner will it be filled. The 

 time, therefore, that sluice B takes to shut after valve N shuts, will always 

 be the same as the time that pipe EN and cylinder EH take to fill when 

 valve N is shut; and to make sluice B take an equal length of time 

 to open after valve N opens, the aperture of that valve must be such as to 

 take an equal length of time to run off" the water to the bottom of cylinder 

 EH, while the water is still flowing into the aperture at I, as that aperture 

 takes to fill both cylinder and pipe when valve N is shut. 



7. Description of a Chain Sluice, invented by Robert Thom, Esq. Rothe- 

 say. 



This apparatus (Plate I. Fig. 10,) answers exactly the same purpose as 

 the last, only the construction is different. 



In this figure, the relative situations of the reservoir and canal are the 

 same as in Fig. 6 ; and the cylinder and valves the same as those in Fig. 

 4, with the addition of RS, a lever, SP, a chain, and U a weight. 



One end of the lever RS is connected with the valve spindle NO, and 

 the other end with the chain SP. The other end of this chain is connected 

 with the float P on the canal XY below. 



When the water in the canal XY rises, float P also rises and slackens 

 the chain SP ; the weight U, then falling, shuts valve O and opens valve 

 N ; then the water, passing down tube KCLD, raises cylinder FG, and 

 the pressure of the water in the reservoir shuts sluice A. When the wa- 



