310 A Mode of Regulating the Supply of Water, fyc. 



therefore advisable, in the construction of such an apparatus, 

 to make the difference of the legs of the syphon double that 

 which the theory requires, and then to reduce the longer to 

 its proper accuracy by absolute experiment. 



The above equation is of more use in the construction of the 

 gauge cistern. The depth above the pipe being assumed 

 greater than is wished, the area of the pipe may be calculated, 

 and the stone be afterwards cut down to the level at which the 

 water is observed to remain. 



When the apparatus is once regulated, the syphon and 

 weights should preserve an exact balance in every point of 

 ascent and descent ; as the accuracy of the discharge depends 

 in a great measure upon that circumstance. If strong catgut, 

 or any light cord, be used to connect the syphon with the 

 weights, the equilibrium may not be sensibly affected by the 

 motion of the syphon. In the present case light chains 

 are used ; and, as the wheels are about two feet in diameter, 

 half a revolution, or a variation of three feet in the level 

 of the canal will take the weight of six feet of chain from one 

 side of the axle, and add it to the other. To obviate this in- 

 convenience, one of the wheels has a piece of lead attached to 

 its side, which is narrower at its extremities than at its centre. 

 W (Fig. 3.) represents the wheel thus loaded, and in its situa- 

 tion when the syphon is at its lowest point. 



It only remains to observe, that this simple apparatus, which 

 is so easily regulated by a little increase or diminution of the 

 weights, has now been at work for more than fourteen years, 

 without any alteration in its adjustment, and to the perfect 

 satisfaction of all parties. A very intense frost has once or 

 twice suspended its operation, but the succeeding thaw has 

 enabled it to resume its function of a constant arbitrator. 



Nottingham, 1826. R. W. A. 



Note. A floating syphon, with wheels and balance weights, 

 is, we believe, fully described in the article ' Hydrodynamics/ 

 in Brewster's Encyclopaedia ; but the date of the article is by 

 much posterior to the first erection of the instrument described 

 above, and which has the authority of twenty years constant 

 use. Editor. 



