Fig. 51 shows a complete plant in section. A is the generator filled with coke or anthracite; the opening of the hopper, N, and the door, D, of the hearth are closed. Air arrives from the centrifugal pump through a stop-valve, I, and water through W. The air passes through the mass of incandescent carbon forming carbonic acid gas, which is again reduced by the excess of carbon to carbon monoxide. The water becomes vaporized, and is dissociated by the action of the heated carbon forming hydrogen and oxygen, which combines with the carbon forming more carbon monoxide. The gas produced consists therefore of carbon monoxide, hydrogen, nitrogen, and a small proportion of hydrocarbons and carbonic acid gas. Passing by the pipe S to the base of the washing-tower the gases meet in their ascent water from the pipe Z, which cleanses them of all impurities, after which they pass by the pipe Y to the gasometer, and from there to the engine. We close this description of gas and oil engines, hoping that we have said enough to put before electrical engineers who are thinking of making use of this economic form of motive power, the exact state of affairs, what results have been obtained, and especially the considerations which govern the choice of an engine. [Illustration: FIG. 52.—Agricultural Oil Locomotive.] We further hope that this systematic examination of all engines which have received the sanction of practical experience, will prove of some service to those who wish to become better acquainted with the numerous existing types, and to understand their relative advantages and faults, in order that they may select a gas engine which is suitable to the particular requirements of each individual case. INDEX Buire-Lencauchez Gas, 110 Carburator, Schrab, 69 ” Delamare, 70 ” Lothhammer, 70 ” Meyer, 69 Carburetted Air Engine, Brouhot, 74 ” Daimler, 73 ” De Dion-Bouton (Tricycle), 75 ” Durand, 71 ” Lenoir, 68 ” Tenting, 71 Carburetted Gas, Faignot, 68 ” Mille, 67 De Dion-Bouton Motor Tricycle, 75 Dowson Gas, 107 Efficiency of Heat Engines, 15