On account of these troubles with the water jackets and the cylinders, it was decided to build some extra cylinders, not only because past experience had suggested improvements in detail in the construction of the jackets, which would prevent to a large extent the great troubles which had been met with in the brazed joints, but also to insure having sufficient cylinders to enable the engine to be always in working condition, even though several of the cylinders might be out of commission from slight imperfections in the jackets or at other points. While the construction of these new cylinders involved a repetition of the arduous task of brazing, yet the minor improvements which were introduced [p237] proved eminently successful in providing against future troubles from leaky jackets. [Illustration: PL. 78 ENGINE OF AERODROME A. SECTION THROUGH CYLINDER AND DRUM] [Illustration: PL. 79 ENGINE OF AERODROME A. END ELEVATION, PORT SIDE] [Illustration: PL. 80 ENGINE OF AERODROME A. TOP PLAN] [Illustration: PL. 81 ENGINE OF AERODROME A. ELEVATION STARBOARD BED PLATE, SPARKING MECHANISM] The general form of construction of the engine with the improved cylinders will be readily understood from the drawings, Plates 78–81, in which Plate 78 is a detail sectional view, previously referred to, through one of the cylinders; Plate 79 is an end elevation of the port side, Plate 80 is a plan view, and Plate 81 is an elevation of the starboard bed plate which supports that side of the engine, and by which it was fastened to the aerodrome frame, this view showing particularly the sparking apparatus which was mounted on the bed plate. The engine consists primarily of a single crank shaft provided with a single crank pin, the shaft having bearings in a drum which consists essentially of two heads. Arranged around the crank shaft and attached at equidistant points of the drum are five cylinders. Mounted on the port side of the crank shaft and close to the crank arm is a small gear, which through suitable gears mounted on the port head of the drum drives a double-pointed cam which has a bearing on the exterior of the hub of the drum. The ratio of these gears is such that the cam is driven at one-quarter the speed of the crank shaft, and in the reverse direction. Mounted on the exterior side of the port head of the drum are five punch rods, the upper ends of which are within a sixty-fourth of an inch of being in contact with the exhaust-valve stems of the cylinders, and on the lower end of these rods are hardened-steel rollers which rest on the double-pointed cam--this one cam thus serving to operate the exhaust valves of all five of the cylinders. The port head of the drum is connected to the port bed plate, by which it is supported, by means of a flanged bushing in which are formed tongues and grooves which fit into corresponding grooves and tongues formed in the hub of the drum, it being necessary to have a certain amount of space between this bed