“From the stamping-plant through the machine, gear-cutting, and grinding shops and welding department, the care with which each engine is turned out is apparent. Take apart a cylinder which has a stamped sheet-metal water-jacket welded externally, and the original billet is found out of which the cylinder was made, but reduced almost by half when it is ready to receive the valve cages, and during the process of removal of the metal and forming into proper shape the piece is subjected to several heat treatments so as to bring the metal to that stage of perfection needed for the work it has to perform. The elbow cages that are fitted to the cylinders might be cast and cored, but the valve cage is an actual solid stamping, and the right-angle bend through the elbow has to be bored out by special machines. “One point illustrates the care in the choice of metal and the multifarious operations through which each part has to pass. A crank-shaft stamping with extension piece on the rear and about one foot long is cut off, and test pieces of this metal, properly numbered with each crank-shaft, are passed through the same treatment as the crank-shaft itself, and then subjected to minute examination by highly skilled engineers. The actual manufacturing side of the work would naturally be very similar to the manufacture of a car engine, but one obtains a better perspective of what an engine is subjected to by passing from the erecting and manufacturing shops to the engine-testing shop, where the ear-splitting reports from the open exhausts of a number of engines being tested at the same time are heard. Here one sees how dissimilar the aviation engine is from the car engine. It is almost impossible, without having actually witnessed it, to picture to oneself a 12-cylinder engine running at 2,200 R. P. M. against a brake test. As the exhaust ports are on either side of the engine, the cylinders being placed in the form of a V, it is possible, by passing on either side, to look into the combustion-chamber and see the valves rising and the spit of the exhaust, and, what is almost incredible, that the exhaust valves are actually red-hot and run in this condition for hours. Little wonder is it that the valves have to be made of superfine material and of particular form. “The variation in the color of the flame of the exhaust, due to strong and weak mixtures, makes it quite possible to test the good running of an engine by the color of its exhaust. The strength of the mixture has necessarily to be altered according to atmospheric conditions and the altitude to which the pilot desires to climb. “No doubt airplane-engine practice of the last four years and the advance that it has made will be reflected in a very marked degree in the automobile, not necessarily by fitting large airplane engines in cars, but by applying to car practice the knowledge that has been gained in manufacture.