There are several distinct types of aircraft engines, based on the arrangement of the cylinders. The “tandem” type has the cylinders standing upright in a row, one behind another. There may be as many as eight in a row. The Curtiss and Wright engines are examples. Another type is the “opposed” arrangement, the cylinders being placed in a horizontal position and in two sets, one working opposite the other. An example of this type is seen in the Darracq motor used on the Santos-Dumont monoplane. Another type is the “V” arrangement, the cylinders set alternately leaning to right and to left, as seen in the “Fiat” engine. Still another type is the “radiant,” in which the cylinders are all above the horizontal, and disposed like rays from the rising sun. The 3-cylinder Anzani engine and the 5- and 7-cylinder R-E-P engines are examples. The “star” type is exemplified in the 5 and 7-cylinder engines in which the cylinders radiate at equal angles all around the circle. The “double opposed” or cross-shaped type is shown in the “Gobron” engine. In all of these types the cylinders are stationary, and turn the propeller shaft either by cranks or by gearing. [Illustration: The Elbridge engine, of the “tandem” type and water-cooled. It is an American engine, built at Rochester, N. Y.] An entirely distinct type of engine, and one which has been devised solely for the aeroplane, is the rotative--often miscalled the rotary, which is totally different. The rotative type may be illustrated by the Gnome motor. In this engine the seven cylinders turn around the shaft, which is stationary. The propeller is fastened to the cylinders, and revolves with them. This ingenious effect is produced by an offset of the crank-shaft of half the stroke of the pistons, whose rods are all connected with the crank-shaft. The entire system revolves around the main shaft as a centre, the crank-shaft being also stationary. [Illustration: The famous Gnome motor; 50 horse-power, 7-cylinder, air-cooled; of the rotative type; made in France. This illustration shows the Gnome steel propeller.] [Illustration: Sectional diagram of the 5-cylinder R-E-P motor; of the “radiant” type.] [Illustration: Sectional diagram of the 5-cylinder Bayard-Clement motor; of the “star” type.] Strictly speaking, the propeller is not a part of the motor of the flying machine, but it is so intimately connected with it in the utilization of the power created by the motor, that it will be treated of briefly in this chapter.