Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/542

526 526 [HYDKAULICS. (9). on entering and leaving the wheel, are completely independent. ; &quot;:Vj.? That the efficiency may be as great as possible, it is obviously gR necessary that ic a = 0. In that case I a? 1 ! is the circumferential velocity of the wheel at the inlet sur Fig. 187. face. Calling this V^ the equation becomes This remarkably simple equation is the fundamental equation in Fig. 188. the theory of turbines. It was first given by Herr v. Reiche (Turbincn-baues, 1877). 173. General Description of a Reaction Turbine. Profes sor James Thomson s inward flow or vortex turbine has been