Every boy and almost every man has longed to ride on a locomotive, and has dreamed of holding the throttle-lever and of feeling the great machine move under him in answer to his will. Many of us have protested vigorously that we wanted to become grimy, hard-working firemen for the sake of having to do with the “iron horse.”

It is this joy of control that comes to the driver of an automobile which is one of the motor-car's chief attractions: it is the longing of the boy to run a locomotive reproduced in the grown-up.

The ponderous, snorting, thundering locomotive, towering high above its steel road, seems far removed from the swift, crouching, almost noiseless motor-car, and yet the relationship is very close. In fact, the automobile, which is but a locomotive that runs at will anywhere, is the father of the greater machine.

About the beginning of 1800, self-propelled vehicles steamed along the roads of Old England, carrying passengers safely, if not swiftly, and, strange to say, continued to run more or less successfully until prohibited by law from using the highways, because of their interference with the horse traffic. Therefore the locomotive and the railroads throve at the expense of the automobile, and the permanent iron-bound right of way of the railroads left the highways to the horse.

The old-time automobiles were cumbrous affairs, with clumsy boilers, and steam-engines that required one man's entire attention to keep them going. The concentrated fuels were not known in those days, and heat-economising appliances were not invented.

It was the invention by Gottlieb Daimler of the high-speed gasoline engine, in 1885, that really gave an impetus to the building of efficient automobiles of all powers. The success of his explosive gasoline engine, forerunner of all succeeding gasoline motor-car engines, was the incentive to inventors to perfect the steam-engine for use on self-propelled vehicles.

Unlike a locomotive, the automobile must be light, must be able to carry power or fuel enough to drive it a long distance, and yet must be almost automatic in its workings. All of these things the modern motor car accomplishes, but the struggle to make the machinery more efficient still continues.

The three kinds of power used to run automobiles are steam, electricity, and gasoline, taken in the order of application. The steam-engines in motor-cars are not very different from the engines used to run locomotives, factory machinery, or street-rollers, but they are much lighter and, of course, smaller—very much smaller in proportion to the power they produce. It will be seen how compact and efficient these little steam plants are when a ten-horse-power engine, boiler, water-tank, and gasoline reservoir holding enough to drive the machine one hundred miles, are stored in a carriage with a wheel-base of less than seven feet and a width of five feet, and still leave ample room for four passengers.

It is the use of gasoline for fuel that makes all this possible. Gasoline, being a very volatile liquid, turns into a highly inflammable gas when heated and mixed with the oxygen in the air. A tank holding from twenty to forty gallons of gasoline is connected, through an automatic regulator which controls the flow of oil, to a burner under the boiler. The burner allows the oil, which turns into gas on coming in contact with its hot surface, to escape through a multitude of small openings and mix with the air, which is supplied from beneath. The openings are so many and so close together that the whole surface is practically one solid sheet of very hot blue flame. In getting up steam a separate blaze or flame of alcohol or gasoline is made, which heats the steel or iron with which the fuel-oil comes in contact until it is sufficiently hot to turn the oil to gas, after which the burner works automatically. A hand air-pump or one automatically operated by the engine maintains sufficient air pressure in the fuel-tank to keep a constant flow.

Most steam automobile boilers are of the water-tube variety—that is, water to be turned into steam is carried through the flames in pipes, instead of the heat in pipes through the water, as in the ordinary flue boilers. Compactness, quick-heating, and strength are the characteristics of motor-car boilers. Some of the boilers are less than twenty inches high and of the same diameter, and yet are capable of generating seven and one-half horse-power at a high steam pressure (150 to 200 pounds). In these boilers the heat is made to play directly on a great many tubes, and a full head of steam is generated in a few minutes. As the steam pressure increases, a regulator that shuts off the supply of gasoline is operated automatically, and so the pressure is maintained.

The water from which the steam is made is also fed automatically into the boiler, when the engine is in motion, by a pump worked by the engine piston. A hand-pump is also supplied by which the driver can keep the proper amount when the machine is still or in case of a breakdown. A water-gauge in plain sight keeps the driver informed at all times as to the amount of water in the boiler. From the boiler the steam goes through the throttle-valve—the handle of which is by the driver's side—direct to the engine, and there expands, pushes the piston up and down, and by means of a crank on the axle does its work.

The engines of modern automobiles are marvels of compactness—so compact, indeed, that a seven-horse-power engine occupies much less space than an ordinary barrel. The steam, after being used, is admitted to a coil of pipes cooled by the breeze caused by the motion of the vehicle, and so condensed into water and returned to the tank. The engine is started, stopped, slowed, and sped by the cutting off or admission of the steam through the throttle-valve. It is reversed by means of the same mechanism used on locomotives—the link-motion and reversing-lever, by which the direction of the steam is reversed and the engine made to run the other way.

After doing its work the steam is made to circulate round the cylinder (or cylinders, if there are more than one), keeping it extra hot—“superheated”; and thereafter it is made to perform a like duty to the boiler-feed water, before it is allowed to escape.

All steam-propelled automobiles, from the light steam runabout to the clumsy steam roller, are worked practically as described. Some machines are worked by compound engines, which simply use the power of expansion still left in the steam in a second larger cylinder after it has worked the first, in which case every ounce of power is extracted from the vapour.

The automobile builders have a problem that troubles locomotive builders very little—that is, compensating the difference between the speeds of the two driving-wheels when turning corners. Just as the inside man of a military company takes short steps when turning and the outside man takes long ones, so the inside wheel of a vehicle turns slowly while the outside wheel revolves quickly when rounding a corner. As most automobiles are propelled by power applied to the rear axle, to which the wheels are fixed, it is manifest that unless some device were made to correct the fault one wheel would have to slide while the other revolved. This difficulty has been overcome by cutting the axle in two and placing between the ends a series of gears which permit the two wheels to revolve at different speeds and also apply the power to both alike. This device is called a compensating gear, and is worked out in various ways by the different builders.

The locomotive builder accomplishes the same thing by making his wheels larger on the outside, so that in turning the wide curves of the railroad the whole machine slides to the inside, bringing to bear the large diameter of the outer wheel and the small diameter of the inner, the wheels being fixed to a solid axle.

The steam machine can always be distinguished by the thin stream of white vapour that escapes from the rear or underneath while it is in motion and also, as a rule, when it is at rest.

The motor of a steam vehicle always stops when the machine is not moving, which is another distinguishing feature, as the gasoline motors run continually, or at least unless the car is left standing for a long time.

As the owners of different makes of bicycles formerly wrangled over the merits of their respective machines, so now motor-car owners discuss the value of the different powers—steam, gasoline, and electricity.

Though steam was the propelling force of the earliest automobiles, and the power best understood, it was the perfection of the gasoline motor that revived the interest in self-propelled vehicles and set the inventors to work.

A gasoline motor is somewhat like a gun—the explosion of the gas in the motor-cylinder pushes the piston (which may be likened to the projectile), and the power thus generated turns a crank and drives the wheels.

The gasoline motor is the lightest power-generator that has yet been discovered, and it is this characteristic that makes it particularly valuable to propel automobiles. Santos-Dumont's success in aerial navigation is due largely to the gasoline motor, which generated great power in proportion to its weight.

A gasoline motor works by a series of explosions, which make the noise that is now heard on every hand. From the gasoline tank, which is always of sufficient capacity for a good long run, a pipe is connected with a device called the carbureter. This is really a gas machine, for it turns the liquid oil into gas, this being done by turning it into fine spray and mixing it with pure air. The gasoline vapour thus formed is highly inflammable, and if lighted in a closed space will explode. It is the explosive power that is made to do the work, and it is a series of small gun-fires that make the gasoline motor-car go.

All this sounds simple enough, but a great many things must be considered that make the construction of a successful working motor a difficult problem.

In the first place, the carbureter, which turns the oil into gas, must work automatically, the proper amount of oil being fed into the machine and the exact proportion of air admitted for the successful mixture. Then the gas must be admitted to the cylinders in just the right quantity for the work to be done. This is usually regulated automatically, and can also be controlled directly by the driver. Since the explosion of gas in the cylinder drives the piston out only, and not, as in the case of the steam-engine, back and forward, some provision must be made to complete the cycle, to bring back the piston, exhaust the burned gas, and refill the cylinder with a new charge.

In the steam-engine the piston is forced backward and forward by the expansive power of the steam, the vapour being admitted alternately to the forward and rear ends of the cylinder. The piston of the gasoline engine, however, working by the force of exploded gas, produces power when moving in one direction only—the piston-head is pushed out by the force of the explosion, just as the plunger of a bicycle pump is sometimes forced out by the pressure of air behind it. The piston is connected with the engine-crank and revolves the shaft, which is in turn connected with the driving-wheels. The movement of the piston in the cylinder performs four functions: first, the downward stroke, the result of the explosion of gas, produces the power; second, the returning up-stroke pushes out the burned gas; third, the next down-stroke sucks in a fresh supply of gas, which (fourth) is compressed by the following-up movement and is ready for the next explosion. This is called a two-cycle motor, because two complete revolutions are necessary to accomplish all the operations. Many machines are fitted with heavy fly-wheels, the swift revolution of which carries the impetus of the power stroke through the other three operations.

To keep a practically continuous forward movement on the driving-shaft, many motors are made with four cylinders, the piston of each being connected with the crank-shaft at a different angle, and each cylinder doing a different part of the work; for example, while No. 1 cylinder is doing the work from the force of the explosion, No. 2 is compressing, No. 3 is getting a fresh supply of gas, and No. 4 is cleaning out waste gas. A four-cylinder motor is practically putting forth power continuously, since one of the four pistons is always at work.

While this takes long to describe, the motion is faster than the eye can follow, and the “phut, phut” noise of the exhaust sounds like the tattoo of a drum. Almost every gasoline motor vehicle carries its own electric plant, either a set of batteries or more commonly a little magneto dynamo, which is run by the shaft of the motor. Electricity is used to make the spark that explodes the gas at just the right moment in the cylinders. All this is automatic, though sometimes the driver has to resort to the persuasive qualities of a monkey-wrench and an oil-can.

The exploding gas creates great heat, and unless something is done to cool the cylinders they get so hot that the gas is ignited by the heat of the metal. Some motors are cooled by a stream of water which, flowing round the cylinders and through coils of pipe, is blown upon by the breeze made by the movement of the vehicle. Others are kept cool by a revolving fan geared to the driving-shaft, which blows on the cylinders; while still others—small motors used on motor bicycles, generally—have wide ridges or projections on the outside of the cylinders to catch the wind as the machine rushes along.

The inventors of the gasoline motor vehicles had many difficulties to overcome that did not trouble those who had to deal with steam. For instance, the gasoline motor cannot be started as easily as a steam-engine. It is necessary to make the driving-shaft revolve a few times by hand in order to start the cylinders working in their proper order. Therefore, the motor of a gasoline machine goes all the time, even when the vehicle is at rest. Friction clutches are used by which the driving-shaft and the axles can be connected or disconnected at the will of the driver, so that the vehicle can stand while the motor is running; friction clutches are used also to throw in gears of different sizes to increase or decrease the speed of the vehicle, as well as to drive backward.

The early gasoline automobiles sounded, when moving, like an artillery company coming full tilt down a badly paved street. The exhausted gas coughed resoundingly, the gears groaned and shrieked loudly when improperly lubricated, and the whole machine rattled like a runaway tin-peddler. Ingenious mufflers have subdued the sputtering exhaust, the gears are made to run in oil or are so carefully cut as to mesh perfectly, rubber tires deaden the pounding of the wheels, and carefully designed frames take up the jar.

Steam and gasoline vehicles can be used to travel long distances from the cities, for water can be had and gasoline bought almost anywhere; but electric automobiles, driven by the third of the three powers used for self-propelled vehicles, must keep within easy reach of the charging stations.

Just as the perfection of the gasoline motor spurred on the inventors to adapt the steam-engine for use in automobiles, so the inventors of the storage battery, which is the heart of an electric carriage, were stirred up to make electric propulsion practical.

The storage battery of an electric vehicle is practically a tank that holds electricity; the electrical energy of the dynamo is transformed into chemical energy in the batteries, which in turn is changed into electrical energy again and used to run the motors.

Electric automobiles are the most simple of all the self-propelled vehicles. The current stored in the batteries is simply turned off and on the motors, or the pressure reduced by means of resistance which obstructs the flow, and therefore the power, of the current. To reverse, it is only necessary to change the direction of the current's flow; and in order to stop, the connection between motor and battery is broken by a switch.

Electricity is the ideal power for automobiles. Being clean and easily controlled, it seems just the thing; but it is expensive, and sometimes hard to get. No satisfactory substitute has been found for it, however, in the larger cities, and it may be that creative or “primary” batteries both cheap and effective will be invented and will do away with the one objection to electricity for automobiles.

The astonishing things of to-day are the commonplaces of to-morrow, and so the achievements of automobile builders as here set down may be greatly surpassed by the time this appears in print.

The sensations of the locomotive engineer, who feels his great machine strain forward over the smooth steel rails, are as nothing to the almost numbing sensations of the automobile driver who covered space at the rate of eighty-eight miles an hour on the road between Paris and Madrid: he felt every inequality in the road, every grade along the way, and each curve, each shadow, was a menace that required the greatest nerve and skill. Locomotive driving at a hundred miles an hour is but mild exhilaration as compared to the feelings of the motor-car driver who travels at fifty miles an hour on the public highway.

Gigantic motor trucks carrying tons of freight twist in and out through crowded streets, controlled by one man more easily than a driver guides a spirited horse on a country road.

Frail motor bicycles dash round the platter-like curves of cycle tracks at railroad speed, and climb hills while the riders sit at ease with feet on coasters.

An electric motor-car wends the streets of New York every day with thirty-five or forty sightseers on its broad back, while a groom in whipcord blows an incongruous coaching-horn in the rear.

Motor plows, motor ambulances, motor stages, delivery wagons, street-cars without tracks, pleasure vehicles, and even baby carriages, are to be seen everywhere.

In 1845, motor vehicles were forbidden the streets for the sake of the horses; in 1903, the horses are being crowded off by the motor-cars. The motor is the more economical—it is the survival of the fittest.