[Illustration: FIG. 4. PLAN AND ELEVATION OF UNDERBERG MOTOR VOITURETTE.] This diagrammatic arrangement is more simple than the gearing actually used and is not as complete in action as many of the devices, as it only provides means whereby the direction of rotation of the axle may be changed, while in many carriages the gearing also varies the ratio between the speed of the motor and the driving wheels. It is also quite common to combine in the train of gearing spur gears and sprocket wheels, and in some instances even belts. Fig. 4 illustrates a French gasoline automobile made by Underberg, of Nantes. The first figure is a side view, and the second is a plan of the truck and driving mechanism. [Illustration: FIG. 5. CHERRIER TWO-SPEED GEAR.] The motor, which is of the single cylinder type, cooled by radiation into the air, is located at _N_. The pinion on the end of the motor shaft engages with the wheel on the end of shaft _A_. This shaft carries four gears, which can be moved by means of lever _C_, so as to engage with corresponding gears on shaft _B_, thus providing four different speeds. The motion of _B_ is transmitted to the rear axle by means of a belt that runs over the pulleys _p_ and _P_, the latter being carried by a differential gear, so as to run the two driving wheels at proper velocities. The circular ribs surrounding the motor cylinder are well shown in the figure, in which the carburator of _C_ is also seen. The housing for the motor is open at the sides so as to give air currents free access. In Fig. 4 the speed changing gears are shown, the reversing train being omitted; but if it were also drawn in, the diagram would be far more elaborate than Fig. 3. Another form of variable speed gear is shown in Fig. 5. This provides for two speeds. The large wheel _E_ is on the carriage axle, and it is driven either by a pinion _F_, or by _J_. Upon the shaft _O_ there are two friction clutches _C D_, and when _C_ acts the pinion _F_ drives _E_, and when _D_ acts the pinion _G_ drives _H_, which in turn drives _I_, and this wheel is mounted on the same shaft as _J_. Some of the best-known makers of gasoline vehicles do not employ variable gears and depend for changes in the speed wholly upon variation in the velocity of the motor. The De Dion carriages are made in this way, the gearing being substantially as illustrated in Fig. 3. [Illustration: FIG. 6. PANHARD & LEVASSOR VEHICLE.] [Illustration: FIG. 7. MOTOR OF VEHICLE.]