The basic intake manifold (see Figure 5) consisted of a very low flat box of sheet steel which ran across the tops of the valve boxes and was directly connected to the top of each of them so that the cages, and thus the valves, were open to the interior of the manifold. Through an opening in the side toward the engine the manifold was connected to a flat induction chamber (21, Figure 5) which served to vaporize the fuel and mix it with the incoming air. This chamber was formed by screw-fastening a piece of sheet steel to vertical ribs cast integral with the crankcase, the crankcase wall itself thus forming the bottom of the chamber. A beaded sheet-steel cylinder resembling a can (73, Figure 6) but open at both ends was fastened upright to the top of this chamber. In the absence of anything else, this can could be called the carburetor, as a fuel supply line entered the cylinder near the top and discharged the fuel into the incoming air stream, both the fuel and air then going directly into the mixing chamber. The can was attached near one corner of the chamber, and vertical baffles, also cast integral with the case, were so located that the incoming mixture was forced to circulate over the entire area of exposed crankcase inside the chamber before it reached the outlet to the manifold proper, the hot surface vaporizing that part of the fuel still liquid. [Illustration: _Figure 7._--First flight engine, 1903: cylinder, valve box, and gear mechanism; below, miscellaneous parts. (Photos courtesy Science Museum, London, and Louis P. Christman.)] Fuel was gravity fed to the can through copper and rubber tubing from a tank fastened to a strut, several feet above the engine. Of the two valves placed in the fuel line, one was a simple on-off shutoff cock and the other a type whose opening could be regulated. The latter was adjusted to supply the correct amount of fuel under the desired flight operating condition; the shutoff cock was used for starting and stopping. The rate of fuel supply to the engine would decrease as the level in the fuel tank dropped, but as the head being utilized was a matter of several feet and the height of the supply tank a matter of inches, the fuel-air ratio was still maintained well within the range that would ignite and burn properly in the contemplated one-power condition of their flight operation.