roller shaft. Under the gas roller and on the camshaft there is (8) a cam; the roller shaft, which is hollow, slips over (9) the pin of a crank, or roller lever, as it is called, and finally this is fixed to (10) the gas valve lever, the arm of which rests on the end of the gas valve poppet, all of which are shown at A and B, in Fig. 31.

The Way It Works.-When the engine is running the balls are rotated by the vertical shaft by means of the beveled gears and the weight tends to hold the shaft down against the centrifugal force which makes them fly apart.

When the balls spread apart they lift up the grooved sleeve and, as the fork of the horizontal lever rests in the groove, it moves up with it; in turn this moves the vertical forked lever, which is fastened to it sidewise. When this action takes place the fork slides the roller over and makes it miss the cam on the camshaft.

The result is that the gas valve lever remains closed and hence the gas valve misses, that is, it does not take in any gas on the suction stroke.

But as long as the speed is right the balls do not fly apart wide enough to throw over the lever and the roller, the cam strikes it and the gas valve lever opens the gas valve.

The Throttling Governor.-This governor also has a pair of flyballs which are rotated in the same way as in the governor described above. The vertical shaft with the grooved sleeve works a lever that

opens and closes a gas valve, or throttle, as it is called, in the gas supply pipe more or less in order to keep the speed uniform. It is shown in Fig. 13.

How the Engine is Oiled. The chief parts of the engine to be oiled are (1) the piston, (2) the crankshaft bearings, and (3) the connecting rod bearings. Besides, there are numerous other smaller moving parts which must be lubricated.

FIG. 32. HOW THE ENGINE IS OILED

A, Cross Section of a Sight Feed Oil Cup. B, Wipe Oiler for Connecting Rod Bearing on Piston. C, A Ring Oiler for Crankshaft Bearing.

The piston and the wrist pin are lubricated by a sight feed oil cup, that is, an oil cup which feeds down the oil drop by drop and which has a glass window in it so that you can see the rate at which the oil flows. An oil cup of this kind has either a regulating screw, or a handle, on top, so that the oil can be fed as fast or as slow as it is needed, or shut off entirely. It is shown at A and B in Fig. 32, and its position on the cylinder is shown at B. The

piston has a groove cut in its periphery and as this passes the oil duct it fills with oil, and so lubricates the piston and the cylinder.

The bearing of the connecting rod on the wrist pin is lubricated by an oil tube from the same oil cup, which sets in the piston over and directly in a line with an oil pipe in the bearing, and this is also shown at B.

The bearings of the crankshaft are lubricated either by (1) sight feed oil cups or (2) by ring oilers. A ring oiler has an oil well, or reservoir, which is filled with oil and a metal ring which is large enough so that when it is hung on the shaft the lower edge dips into the oil, as shown at C.

As the shaft revolves the ring turns a little at a time with it and carries oil to the bearing as it moves round. With this system of oiling there is never any danger of hot boxes.

The bearings of the connecting rod on the crankshaft are oiled by a wiper oiler. A sight feed oil cup is mounted on an upright rod, or on the crankguard, that is, a heavy metal sheet arched over the crank. The wiper consists of an oil tube set in the crank-pin bearing and having in it a piece of lampwick.

As the crank revolves, the lampwick strikes the open end of the oil cup pipe and wipes off the oil. When the wick is soaked with oil it reaches the bearing and the crankpin and keeps them lubricated.

The numerous other small parts to be lubricated

are oiled by small oil cups or by hand through oil holes.

Kinds of Water Circulating Systems.-There are two simple ways to keep water circulating around

FIG. 33. COOLING BY A STEADY FLOW OF WATER

'A, End View of the Engine. B, Side View of the Engine. C, Top View of the Engine.

the cylinder to keep it cool, and these are (1) by using a stream of city water, or water that is under pressure from any other source, and (2) by employing a water tank.

Using a Steady Flow of Water.-Where a steady

flow of water can be had it is simply piped into the cylinder jacket through a cock at its lower end; the heated water is then carried off by a spout near the top of the jacket, as shown at A, B and C in Fig. 33, when it empties into a funnel and is carried away by the waste pipe to a sewer.

FIG. 34. TANK OR THERMO-SIPHON COOLING SYSTEM

The Cooling Tank, or Thermo-Siphon System.Where flowing water is not available engines of from 1 to 15 horsepower can be cooled by means of a tank, as shown in Fig. 34.

When the water in the cylinder jacket heats up it gets lighter and rises through the pipe into the tank, while the cold water, since it is the heaviest, falls to the bottom of the tank and then flows on back into the cylinder jacket. In this way the water is