plished by cutting off the current from the sparking device or by varying or timing the point of ignition. In Fig. 115 is illustrated a form of governor which operates by preventing the exhaust valve from opening. When the speed of the engine exceeds its normal limit, the balls A move outward, causing the cam B to be moved to the right by the action of the dogs C on the

H

G

F

Fig. 115.-Exhaust Valve Governor

governor arms D, which are held in a grooved collar E on the sleeve F. The end of the cam B is thus prevented from acting on the roller G, until the motor falls to its normal speed, thus preventing the valve mechanism from operating the valve. Ordinarily the cam is held in position by the springs fastened to the governor balls, which hold the cam against the shoulder of the bearing I of the cam shaft J.

Another form of governor, shown in Fig. 116, may be used in connection with any of the governing methods mentioned, but is particularly adapted to throttling methods. The two balls A, A are rotated through any

B

H

-B

Fig. 116.-Throttling Gov

ernor

convenient method of connection with the motor, and in the illustration are represented connected by bevel gears B, B. As the speed of the motor increases the balls swing outward as indicated by the arrows, thus compressing the spring C, and pushing down the stem D, by means of the collar E; as the rod moves down, the valve F, at its lower end, moves past the holes G, H, which admit the charge of vapor, and thus gradually throttles the charge that passes to the engine through

H.

In Fig. 117 is shown a

governor which operates on the hit-or-miss principle. When the motor races or runs beyond the normal speed the action of the balls causes the blade A to move away from the notched valve lifter B, thus throwing the valve out of action. A governor of the inertia type is illustrated in Fig. 118. In this form, if the engine attempts to run above normal speed,

the lower end of the double lever A will be depressed by the cam B, and the valve lift C will be thrown out of engagement with the shoulder D, thus preventing any action of the valve until the motor speed drops to normal. Various other forms of governors are in use and these may be attached to a bracket fastened to the engine frame or may be bolted to the fly-wheel or cam shaft. In the Twentieth Century motors a centrifugal governor

is fastened to the fly-wheel and through properly adjusted springs and rods is connected with the carburetor throttle. Governors are usually properly adjusted to give the best results when the motors leave the makers; and unless they become loose, broken or worn, or very evidently out of adjustment they should not be meddled with. As most governors depend to a large extent upon spring action, any rust, corrosion, or dirt on the latter is liable to affect the operation of the governor, and care should be taken that they are kept free from dirt and rust. They should also be frequently lubricated, but good machine oil and not cylinder oil should be used for this purpose.

Various fuels are used in operating internal-combustion engines and practically any grade of gasolene, benzine, or naphtha may be used to operate a gasolene motor with slight variations in carburetor adjustments. Poor, stale, or dirty gasolene will often give poor results, and as a rule the lower grades are not so economical as the better grades. Moreover, poor fuel results in an excess

B

C

Fig. 118.-Inertia Governor

of carbon and soot and should be avoided as far as possible. Many gasolene motors will run very well on denatured alcohol or kerosene if first started with gasolene. There is really but little reason for using these as fuel, however, for gasolene gives so much better results and so much less soot and carbon that it more than makes up for the additional first cost. Sometimes, however, the operator of a motor will find himself short

of fuel where no gasolene can be purchased. At such times, if the motor is started and well heated on gasolene, kerosene or alcohol may be used. It is always a good plan to carry a small quantity of your regular gasolene for use in an emergency, and this should never be used until absolutely necessary. The fuel consumption of a gasolene motor depends a great deal upon the care with which the carburetor is adjusted in order to use the minimum amount of fuel to obtain the best results; the accurate timing of valves and ignition, and the original design and construction of the motor. A two-cycle motor will use more fuel than a four-cycle, and a multiple-cylinder motor will use more than the same number of separate cylinders. Another item which enters quite largely into fuel consumption is the temperature of the cylinder. The best results are obtained when the temperature of the water in the jacket is kept at about 160 degrees Fahrenheit. With this temperature, high-grade fuel, and careful operation the average engine will consume about 1 1/5 pints of gasolene, or about 15 ft. of natural gas, per horse-power per hour under full load. Engines that will burn gas satisfactorily will usually burn gasolene, and vice versa, but it is best to have the motor arranged to consume a certain kind and quality of fuel. Many manufacturers provide devices for using kerosene in gasolene motors; and if kerosene is to be used it is far better to use such a device, or else purchase a regular oil engine, than to try to operate a motor intended for gasolene or gas by crude oil or kerosene.

Many operators of gasolene engines give very little care to the oil and grease used as lubricants. This is