The windmill is worthy of attention in connection with the possibility of trans mitting and storing the energy generated. Combined with storage, the best site for the mill may be chosen, and the energy delivered where required at any reasonable distance. The water turbines selected for description are the latest of their types, with special reference to governing. Injectors and centrifugal pumps are shortly discussed. These, although not prime movers, are important impulse machines closely connected with prime movers operating by momentum and ?uid velocities.