Beer, To prevent, from turning sour while on draft.-A slate cistern is made, having a wooden lid, fitting accurately, floating on the surface of the liquid. The sides of the lid are beveled, so that a sharp edge is presented to the walls of the cistern, and along this edge a strip of india-rubber is fastened, which forms, with the bevel on the upper side, a V-shaped space, into which wet sand is packed in order to keep the rubber in close contact with the sides of the cistern, and so to exclude the air from the same. A hole is formed in the lid, having a stuffing-box, through which a pipe passes into the liquid, and the connection to the beer-engine is made in the usual way. The end of the pipe in the liquid is closed, but perforations are made in the sides about an inch therefrom: this prevents any sediment escaping with the fluid. Atmospheric pressure, acting on the lid, forces it to descend as the liquid is removed from under it, and thus a constant flow is obtained by means of the engine. By letting the cistern into the ground, the temperature of the liquid will remain nearly uniform the year round.