Every car carries at least two brakes of band pattern—one, usually worked by a side hand-lever, acting on the axle or hubs of the driving-wheel; the other, operated by the foot, acting on the transmission gear (see Fig. 48). The latter brake is generally arranged to withdraw the clutch simultaneously. Tests have proved that even heavy cars can be pulled up in astonishingly short distances, considering their rate of travel. Trials made in the United States with a touring car and a four-in-hand coach gave 25⅓ and 70 feet respectively for the distance in which the speed could be reduced from sixteen miles per hour to zero.
SPEED OF CARS.
As regards speed, motor cars can rival the fastest express trains, even on long journeys. In fact, feats performed during the Gordon-Bennett and other races have equalled railway performances over equal distances. When we come to record speeds, we find a car, specially built for the purpose, covering a mile in less than half a minute. A speed of over 120 miles an hour has actually been reached. Engines of 150 h.p. can now be packed into a vehicle scaling less than 1½ tons. Even on touring cars are often found engines developing 40 to 60 h.p., which force the car up steep hills at a pace nothing less than astonishing. In the future the motor car will revolutionize our modes of life to an extent comparable to the changes effected by the advent of the steam-engine. Even since 1896, when the "man-with-the-flag" law was abolished in the British Isles, the motor has reduced distances, opened up country districts, and generally quickened the pulses of the community in a manner which makes it hazardous to prophesy how the next generation will live.
Note.—The author is much indebted to Mr. Wilfrid J. Lineham, M. Inst. C.E., for several of the illustrations which appear in the above chapter.
Chapter V.
ELECTRICAL APPARATUS.
What is electricity?—Forms of electricity—Magnetism—The permanent magnet—Lines of force—Electro-magnets—The electric bell—The induction coil—The condenser—Transformation of current—Uses of the induction coil.
WHAT IS ELECTRICITY?
Of the ultimate nature of electricity, as of that of heat and light, we are at present ignorant. But it has been clearly established that all three phenomena are but manifestations of the energy pervading the universe. By means of suitable apparatus one form can be converted into another form. The heat of fuel burnt in a boiler furnace develops mechanical energy in the engine which the boiler feeds with steam. The engine revolves a dynamo, and the electric current thereby generated can be passed through wires to produce mechanical motion, heat, or light. We must remain content, therefore, with assuming that electricity is energy or motion transmitted through the ether from molecule to molecule, or from atom to atom, of matter. Scientific investigation has taught us how to produce it at will, how to harness it to our uses, and how to measure it; but not what it is. That question may, perhaps, remain unanswered till the end of human history. A great difficulty attending the explanation of electrical action is this—that, except in one or two cases, no comparison can be established between it and the operation of gases and fluids. When dealing with the steam-engine, any ordinary intelligence soon grasps the principles which govern the use of steam in cylinders or turbines. The diagrams show, it is hoped, quite plainly "how it works." But electricity is elusive, invisible; and the greatest authorities cannot say what goes on at the poles of a magnet or on the surface of an electrified body. Even the existence of "negative" and "positive"