This book is an interesting article into the beginnings of the internal combustion engine. The book contains illustrations and may have some typos. From the Author; The constantly increasing use of gas-engines in the last decade has led to the invention of a great number of types, the operation and care of which necessitate a special practical knowledge that is not exacted by other motors, such as steam-engines. Explosion-engines, driven by illuminating-gas, producer-gas, oil, benzin, alcohol and the like, exact much more care in their operation and adjustment than steam-engines. Indeed, steam-engines are regularly subjected to comparatively low pressures. The temperature in the cylinders, moreover, is moderate. On the other hand, the explosion-motor is irregularly subjected to high and low pressures. The temperature of the gases at the moment of explosion is exceedingly high. It is consequently necessary to resort to artificial means for cooling the cylinder; and the manner in which this cooling is effected has a very great influence on the operation of the motor. If the cooling be effected too rapidly, the quantity of gas consumed is considerably increased; if the cooling be effected too slowly, the motor parts will quickly deteriorate. In order to reduce the gas consumption to a minimum, a matter which is particularly important when viii the motor is driven by street-gas, the explosive mixture is compressed before ignition. Only if all the parts are built with joints absolutely gas-tight is it possible to obtain this compression. The slightest leakage past the valves or around the piston will sensibly increase the consumption. The mixture should be exploded at the exact moment the piston starts on its working stroke. If ignition occurs too soon or too late, the result will be a marked diminution in the useful effect produced by the expansion of the gas. All ignition devices are composed of delicate parts, which cannot be too well cared for. It follows from what has thus far been said that the causes of perturbation are more numerous in a gas than in a steam engine; that with a gas-engine, improper care will lead to a much greater increase in consumption than with a steam-engine, and will cause a waste in power which would hardly be appreciable in steam-engines, whether their joints be tight or not. It is the purpose of this manual to indicate the more elementary precautions to be taken in the care of an engine operating under normal conditions, and to explain how repairs should be made to remedy the injuries caused by accidents. Engines which are of less than 200 horse-power and which are widely used in a small way will be primarily considered. In another work the author will discuss more powerful engines. Before considering the choice, installation, and operation of a gas-engine, it will be of interest to ascertain ix the relative cost of different kinds of motive power. Disregarding special reasons which may favor the one or the other method of generating power, the net cost per horse-power hour will be considered in each case in order to show which is the least expensive method of generating power in ordinary circumstances. R. E. MATHOT. March, 1905.