between intersecting Rivulets and Canals. 309 



tity proved to be 11 .25 cubic feet per minute ; but a great diffi- 

 culty now arose respecting an impartial mode of supply, and 

 this difficulty appeared greater in consequence of the failure 

 of the former plan. At length the dispute was amicably 

 adjusted by the following method, which was invented and 

 carried into execution by Mr. Robert Almond, of Nottingham, 

 then one of the proprietors of the Nottingham Canal. 



A (Fig. 2.) represents a pipe placed under the haling path 

 of the Nottingham Canal, having the end, which communi- 

 cates with the canal, turned downwards to prevent stones and 

 dirt from falling into it. Its other extremity is connected with 

 a large cast iron vessel B, in which the water necessarily rises 

 to the level of that in the canal. C is a copper syphon, 

 balanced in such a manner, partly by means of a hollow 

 copper sphere, through which it passes, and partly by two 

 weights passing over the wheels, as represented in the draw- 

 ing, that it rises and falls freely with the water in the canal. 

 By this contrivance, the discharging orifice of the syphon will 

 always be at equal depths below the surface of the water in the 

 canal, and must therefore constantly deliver equal quantities 

 in equal times. D is a stone cistern, into which the water 

 runs, after being discharged from the syphon, and which serves 

 as a gauge, open to the inspection of passengers. On its inte- 

 rior side, a plabe of copper is placed perpendicular to the plane 

 of the section, and which is made visible by the stone being cu t 

 down to its edge. The water always remains level with this 

 plate, whilst a discharge is taking place from the pipe P. 



It must appear to every one versed in hydraulics, that, 

 owing to the friction of the water against the sides of the 

 syphon, its velocity must be retarded, and that the discharging 

 leg must be longer than the theory of emptying vessels would 

 lead us to suppose. This remark is verified by the case before 

 us. The internal diameter of the syphon is 2.45 inches, and 

 the lower orifice is 21.03 inches beneath the level of the canal; 

 but, according to the theory, which supposes that the velocity 

 at the orifice is that acquired by a body falling from rest 

 through a space equal to half the depth of fluid above it, the 



depth of the lower orifice = qU&ntlty discharged per 1^ _ 



area of orifice") 2 x 386 

 12.22, &c., each term being expressed in inches. It is 



