The problem of keeping joints tight, and for that matter the entire construction itself, were both greatly simplified by their decision to water-jacket only a part of the cylinder head proper, and the valve box not at all. This was undoubtedly the correct decision for their immediate purpose, as again they were effecting savings in time, cost, complexity, and weight. There is nothing in the record, however, to show why they continued this practice long after they had advanced to much greater power outputs and longer flight times. Their own statements show that they were well aware of the effect of the very hot cylinder head on power output and they must also have realized its influence on exhaust-valve temperature. The cylinder assembly was made somewhat more complicated by their desire to oil the piston and cylinder by means of holes near the crankshaft end in what was, with the engine in the horizontal position, the upper side of the cylinder barrel. This complication was no doubt taken care of by not drilling the holes until a tight assembly had been made by screwing the barrel into place, and by marking the desired location on the barrel. Since this position was determined by a metal-to-metal jam fit of the crankcase and cylinder barrel flange, the barrel would reassemble with the holes in very nearly the same relative position after disassembly. With the valve box, or housing, cylindrical, the task of locking and fastening the intake and exhaust valve guides and seats in place was easy. The guide was made integral with and in the center of one end of a circular cage, the other end of which contained the valve seat (see Figure 5). Four sections were cut out of the circular wall of the cage so that in effect the seat and guide were joined by four narrow legs, the spaces between which provided passages for the flow of the cylinder gases. These cages were then dropped into the ends of the valve boxes until they came up against machined shoulders and were held in place by internal ring nuts screwed into the valve box. The intake manifold or passage was placed over the intake valves so that the intake charge flowed directly into and through the valve cage around the open valve and into the cylinder. The exhaust gas, after flowing through the passages in the valve cage, was discharged directly to the atmosphere through a series of holes machined in one side of the valve box. [Illustration: _Figure 5._--First flight engine, 1903, assembly. (Phantom cutaway by J. H. Clark, with key, courtesy _Aeroplane_.) KEY 1 and 2. Bearing caps in one piece with plate 3. 3. Plated screwed over hole 4 in crankcase end. 4. Key-shaped hole as hole 5 in intermediate ribs. 6. Inter-bearings cap (white-metal lined) and screwed to inter-rib halves 7. 8. Splash-drip feed to bearings. 9. Return to pump from each compartment of crankcase base ("sump") via gallery 10 and pipe to pump 11 underneath jacket. 12. Oil feed from pump via rubber tube 13.