344 History of Mechanical Inventions and 



DE, a light can of copper, (or tin plate painted,) open at top, with a 

 small aperture in its bottom. 



F, a pulley. 



G, a lever attached to sluice BC. 



DFG, a chain, which, passing over pulley F, has one end fixed to can 

 DE, and the other to lever G. 



IK, the section of a rivulet, near where it enters the reservoir, in the 

 vicinity of AB. 



LMN, a pipe which communicates between the rivulet at IK and die 

 can DE. 



OP, another pipe, which communicates between pipe LMN and a se- 

 cond can, the same as DE, not shown on the drawing. 



QR, a third pipe, which communicates between pipe LMN and a third 

 can, the same as DE, not shown on the drawing. 



1, 2, 3, apertures that communicate between rivulet IK and pipe LM. 



When can DE is full of water, it shuts sluice BC, but when empty, the 

 pressure of water in front of BC throws it open. The aperture in the 

 bottom of the can DE keeps it always empty, except when the quantity 

 running into it is more than that aperture can pass. 



Before proceeding with the description, it may be proper to explain 

 more fully the object in view. It has been already mentioned, that in 

 this case a number of streams fall into the aqueduct between the reservoir 

 and the mills. When the weather is very wet, these streams furnish a, 

 sufficient supply of themselves ; and at such times, therefore, no water 

 should be allowed to flow from the reservoir. But, when less rain falls, 

 these streams only furnish a part, and the rest must be supplied by the 

 reservoir ; and when the weather is very dry, these streams cease to flow 

 altogether, and then the whole supply must come from the reservoir. 

 Now, this apparatus is so contrived, that, when these streams are en- 

 tirely dry, it sends down the whole supply from the reservoir ; when 

 these streams furnish a part, it sends down the remaining part, whatever 

 it may be ; and when these streams furnish the whole supply, it shuts the 

 reservoir altogether, so that the mills have always an equal supply, whe- 

 ther the weather be wet or dry. 



To accomplish this, the whole number of sluices, BC, &c. placed on 

 the aqueduct AB, are calculated so as just to pass the whole quantity of 

 water wanted at the mills ; and as more or less water is produced by these 

 streams, a greater or lesser number of these sluices will open or shut, so 

 as to keep the quantity at the mills always equal. The number of these 

 sluices will be more or less, as the case may require ; in this we suppose 

 three, as being sufficient to illustrate the principle. 



Let us suppose, then, the weather very dry ; the streams between the 

 reservoir and the mills quite dried up ; and the sluices BC, &c. all open ; 

 rain comes, and these streams begin to flow ; but the same rains that 

 swell these streams, swell also the rivulet IK ; and by the time the first 

 produce a quantity equal to what one sluice (BC) can pass, the last will 

 have risen so as to flow out at aperture 1, thence down pipe LMN into 



