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XXII. On the steady Flow of a Liquid. By Henry Moseley, 

 M.A.y D.C.L., Canon of Bristol, F.R.S., Corresponding Mem- 

 ber of the Institute of France, fyc.* 



THE hydraulic experiments of M. Darcy, continued after his 

 death by M. Bazin, were made with remarkable industry 

 and scientific skill, and on a large scale. In the first series f 

 circular pipes were used, and they were placed horizontally. In 

 the second J the channels were rectangular, open and closed, and 

 they were sloped. The experiments of the first series, which are 

 those referred to in the following paper, were made with pipes 

 of different materials, in different states of roughness or smooth- 

 ness of internal surface, and of different diameters, from ^ inch 

 to 20 inches. Their lengths were generally 120 yards, but 

 some of them 60 yards ; and the water was made to traverse 

 them with velocities varying from 1 inch per second to 20 feet. 



All the necessary precautions were taken to determine the 

 mean diameters of these pipes, and to measure the water dis- 

 charged from them. To feed them, it was received from the re- 

 servoirs at Chaillot into a cylindrical vessel 28 metres high, in 

 which it could be made to stand at any required height by 

 opening more or less a cock in the supply-pipe. It passed from 

 the bottom of this reservoir by means of a horizontal pipe 300 

 metres long, into a great horizontal cylinder, 1 metre in dia- 

 meter and 3tt metres long, to one end of which horizontal 

 cylinder were adjusted the pipes to be experimented upon. This 

 cylinder was crossed internally by an iron diaphragm pierced 

 with small holes, through which the water was made to pass that 

 its vis viva might (as far as possible) be destroyed before it en- 

 tered the pipes experimented upon. Pressure- gauges were fixed 

 at four different points of each pipe — the first being placed near 

 the end by which the water escaped from the pipe into the reser- 

 voir of efflux, the second at 50 metres from it, the third at 100 

 metres from the first, the fourth near the point of entrance of 

 the water from the horizontal c}dinder into the pipe at 4*7 me- 

 tres from the third, and the fifth in the horizontal pipe. They 

 were water-gauges. 



The first and third gauges being 100 metres apart, the differ- 

 ence of the heights of the water in these gauges showed, when 

 the flow of the water had become steady, the head of water ne- 

 cessary to overcome the resistances opposed to the flow of that 

 portion of the water in the pipe which intervened between these 



* Communicated by the Author. 



t Recherches Experiment ales relatives au mouvement de Veau dans les 

 Tuyaux. Paris : Bachelier, 1857. 



f Recherches Hydrauliques, par M. Darcy. Continuees par M. Bazin. 

 Paris: Dunot, 1865. 



