The induction and eduction spaces are divided by a sectoral partition; the apertures of admission and discharge on the sides of the cylinders are of similar construction. The surfaces of contact between the cylinders _b_, _l_ and the support _d_ are planed and polished and are made water-tight by the adjusting screws _m_ _m_ of the pivots. When the piston _p_ is at the end of its course in either direction the cylinder and crank are vertical, and the valves all momentarily closed, the openings by which the channels _j_ _j_ communicate with the discharge and supply pipes presenting themselves exactly opposite the solid sectors which separate _h_ from _i_. In the next moment the flow of water will recommence, the cylinder discharging itself from the full side of the piston, and filling anew from the opposite side. Air chambers and relief-valves are used as a provision against counter-pressure and hydraulic shocks. The Brotherhood three-cylinder reciprocating engine is an appliance for producing rotary motion by water-pressure. The working parts of the Brotherhood three-cylinder hydraulic engine consist only of the three pistons and connecting rods, one crank and one rotating balanced valve and spindle which fits into the driver and is turned direct from the crank-pin; there are no glands, stuffing boxes, or oscillating joints. It is shown by Figs. 131, 132. The three cylinders, A (made in one casting) are always open at their inner ends, and are attached to a central chamber, B. They contain three pistons, P, which transmit motion to the crank-pin through the rods, C. The water is admitted and exhausted by means of the circular disc valve, V, having a lignum-vitæ seat. The valve is rotated by the eccentric pin, E. A face view of this valve is shown above the steam chest. It has segmental ports which, in rotating, pass over apertures in the valve seat. There being no dead centers, the engine will start from all positions of the crank-pin, and a uniform motion of the shaft is produced without a flywheel. The pressure is always on the outer end of the piston, so that the rods, C, are in compression, and take up their own wear. This engine is well adapted for transmitting pressure to appliances which are worked intermittently, as, owing to the great speed at which it can be run, it will not only save the loss from friction (where gearing is employed), but will also reduce the friction in the machine itself by enabling the gearing for increasing speed to be dispensed with. The production of this simple hydraulic rotary engine led to its wide application to capstans.