After the clutch engages and the car has traveled about ten feet, pressure on the accelerator is released, and the clutch pedal pulled down quickly, and the lever is then pulled straight back to the _second speed_. USING THE CLUTCH AND SELECTOR.--For the third and fourth speeds the same course is followed. If, in hill climbing, or in going through a heavy stretch of mud or sand, lower speed is required, the clutch is thrown out, and, if traveling on fourth speed, the control lever is quickly pulled to the rear end of the slot, and then the clutch thrown in. If it is on third speed, the clutch is disengaged, the control lever pushed forward, at the same time pressing it inwardly so it will pass through the gate, and then pulling it back to the second speed. [Illustration: Fig. 61. Planetary Transmission.] PLANETARY TRANSMISSION.--Fig. 61 shows the general arrangement of the planetary transmission. The disk A, carries four small planet gears B, B, B, B, the hub C´ of which is attached to the transmission shaft. These four planet wheels mesh with and travel around a central gear C, of the same diameter this gear being attached to the engine shaft D. E is a loosely-revolving drum, with internal teeth, to mesh with the planet wheels B. The drum E, and the disk or planet wheel carrier A, are provided with braking mechanism so that either may be slowed down or entirely stopped. For slow speed E is stationary; for high speed A and E revolve with the gear C; and for reversing A is locked by means of the brake. [Illustration: Fig. 62. Frictional Transmission.] FRICTIONAL TRANSMISSION.--A single illustration will suffice to show the principle involved in _Frictional_ transmission. Fig. 62 represents a driven shaft A, which receives its power from the engine, and on which is mounted a friction wheel B, that is adapted to travel along on the shaft in front of a friction disk C, secured to the transmission shaft D. The shaft A has a spline E, and means are provided at the end of the wheel B to draw it back and forth on the shaft, the slightest movement toward the center of the friction disk C serving to increase the speed of the driven shaft D. CHAPTER IX THE MOTOR This is a subject so vast and comprehensive, that it will require most careful thought and attention in order to get a working idea of the principle. The greatest refinements are resorted to in the building and handling of engines, and more attention is bestowed on this part of the automobile than on any other feature for the following reason: VALUE OF FUEL UTILIZED.--Not more than eighteen per cent. of the value of the fuel is actually utilized. The rest is waste. A gasoline engine is a heat motor,--that is, it derives its power from the expansion of the fuel, and this expansion is produced by the heat.