In 1884 the Count de Dion, working in partnership with Messrs. Bouton and TrÉpardoux, produced a practical steam tricycle. Two years later appeared a somewhat similar vehicle by the same makers which attained the remarkable speed of forty miles an hour. Mr. Serpollet, now famous for his steam cars, built at about the same time a three-wheeled steam tricycle, which also proved successful. But the continuous stoking of the miniature boilers, and the difficulty of keeping them properly supplied with water, prevented the steam-driven cycle from becoming popular; and when the petrol motor had proved its value on heavy vehicles, inventors soon saw that the explosion engine was very much better suited for a light automobile than had been the cumbrous fittings inseparable from the employment of steam.

By 1895 a neat petrol tricycle was on the market; and after the de Dion machines had given proof in races of their capabilities, they at once sprang into popular favour. For the next five years the motor tricycle was a common sight in France, where the excellent roads and the freedom from the restrictions prevailing on the other side of the Channel recommended it to cyclists who wished for a more speedy method of locomotion than unaided legs could give, yet could not afford to purchase a car.

The motor bicycle soon appeared in the field. The earlier types of the two-wheeled motor were naturally clumsy and inefficient. The need of a lamp constantly burning to ignite the charges in the cylinder proved a much greater nuisance on the bicycle than on the tricycle, which carried its driving gear behind the saddle. The writer well remembers trying an early pattern of the Werner motor bicycle in the Champs ElysÉes in 1897, and his alarm when the owner, while starting the blowlamp on the steering pillar, was suddenly enveloped in flames, which played havoc with his hair, and might easily have caused more serious injuries. Riders were naturally nervous at carrying a flame near the handle-bars, so close to a tank of inflammable petrol liable to leak and catch fire.

The advent of electrical ignition for the gaseous charges opened the way for great improvements, and the motor bicycle slowly but surely ousted its heavier three-wheeled rival. Designs were altered; the engine was placed in or below the frame instead of over the front wheel, and made to drive the back wheel by means of a leather belt. In the earliest types the motive force had either been transmitted by belt to the front wheel, or directly to the rear wheel by the piston rods working cranks on its spindle.

The progress of the motor bicycle has, since 1900, been rapid, and many thousands of machines are now in use. The fact that the engines must necessarily be very small compels all possible saving in weight, and an ability to run continuously at very high speeds without showing serious wear and tear. Details have therefore been perfected, and though at the present day no motor cyclist of wide experience can claim immunity from trouble with his speedy little mount, a really well-designed and well-built machine proves wonderfully efficient, and opens possibilities of locomotion to "the man of moderate means" which were beyond the reach of the rider of a pedal-driven bicycle.

In its way the motor cycle may claim to be one of the most marvellous products of human mechanical skill. Weight has been reduced until a power equal to that of three horses can be harnessed to a vehicle which, when stored with sufficient petrol and electricity to carry it and rider 150 miles, scales about a hundredweight. It will pursue its even course up and down hill at an average of twenty or more miles an hour, the only attention it requires being an occasional charge of oil squirted into the air-tight case in which the crank and fly-wheels revolve. The consumption of fuel is ridiculously small, since an economical engine will cover fifteen miles on a pint of spirit, which costs about three-halfpence.

Practically all motor-cycle engines work on the "Otto-cycle" principle. Motors which give an impulse every revolution by compressing the charge in the crank-case or in a separate cylinder, so that it may enter the working cylinder under pressure, have been tried, but hitherto with but moderate success. There is, however, a growing tendency to compass an explosion every revolution by fitting two cylinders, and from time to time four-cylindered cycles have appeared. The disadvantages attending the care and adjustment of so many moving parts has been the cause of four-cylindered cycle motors being unsuccessful from a commercial standpoint, though riders who are prepared to risk extra trouble and expense may find compensation in the quiet, vibrationless drive of a motor which gives two impulses for every turn of the fly-wheel.

The acme of lightness in proportion to power developed has been attained by the "Barry" engine, in which the cylinders and their attachments are made to revolve about a fixed crank, and perform themselves the function of a fly-wheel. So great is the saving of weight that the makers claim a horse-power for every four pounds scaled by the engines; thus, a 3 1 / 2 h.p. motor would only just tip the beam against one stone. As the writer has personally inspected a Barry engine, he is able to give a brief account of its action.

It has two cylinders, arranged to face one another on opposite sides of a central air-tight crank-case, the inner end of each cylinder opening into the case. Both pistons advance towards, and recede from, the centre of the case simultaneously. The air-and-gas mixture is admitted into the crank-case through a hole in the fixed crank-spindle, communicating with a pipe leading from the carburetter. The inlet is controlled by a valve, which opens while the pistons are parting, and closes when they approach one another.

We will suppose that the engine is just starting. The pistons are in a position nearest to the crank-case. As they separate they draw a charge—equal in volume to double the cubical contents of one cylinder—into the crank-case through its inlet valve. During the return stroke the charge is squeezed, and passes through a valve into a chamber which forms, as it were, the fourth spoke of a four-spoked wheel, of which the other three spokes are the cylinders and the "silencer." This chamber is connected by pipes to the inlet valves of the cylinders, which are mechanically opened alternately by the action of special cams on the crank-shaft. The cylinder which gets the contents of the compression chamber receives considerably more "mixture" than would flow in under natural suction, and the compression is therefore greater than in the ordinary type of cycle motor, and the explosion more violent. Hence it comes about that the cylinders, which have a bore of only 2 in. and a 2-in. stroke for the piston, develop nearly 2 h.p. each.

It may at first appear rather mysterious how, if the cranks are rigidly attached to the cycle frame, any motion can be imparted to the driving-wheel. The explanation is simple enough: a belt pulley is affixed to one side of the crank-case, and revolves with the cylinders, the silencer, and compression chamber. The rotation is caused by the effort of the piston to get as far as possible away from the closed end of the cylinder after an explosion. Where a crank is movable but the cylinder fixed, the former would be turned round; where the crank is immovable but the cylinder movable, the travel of the piston is possible only if the cylinder moves round the crank. A series of explosions following one another in rapid succession gives the moving parts of the Barry engine sufficient momentum to suck in charges, compress them, and eject the burnt gases. The plan is ingenious, and as the machine into which this type of engine is built weighs altogether only about 70 lbs., the "sport" of motor cycling is open to those people whose age or want of strength would preclude them from the use of the heavy mounts which are still to be seen about the roads. In the future we may expect to find motor cycles approach very closely to a half-hundredweight standard without sacrificing the rigidity needful for fast locomotion over second-class roads.

For "pace-making" on racing tracks, motor cycles ranging up to 24 h.p. have been used; but these are essentially "freak" machines of no practical value for ordinary purposes. Even 3-4 h.p. cycles have set up wonderful records, exceeding fifty miles in the hour, a speed equal to that of a good express train. In comparison with the feats of motor-cars, their achievements may not appear very startling; but when we consider the small size and weight, and the simplicity of the mechanisms which propel cycle and rider at nearly a mile a minute, the result seems marvellous enough.

During the last few years the tricycle has again come into favour, but with the arrangement of its wheels altered; two steering-wheels being placed in front, and a single driving-wheel behind. The main advantage of this inversion is that it permits the fixing of a seat in front of the driver, in which a passenger can be comfortably accommodated. The modern "tricar," with its high-powered, doubled-cylindered engines, its change-speed gears, its friction clutch for bringing the engines gradually into action, its forced water circulation for cooling the cylinders, and its spring-hung frame, is in reality more a car than a cycle, and escapes from the former category only on account of the number of its wheels. To the tourist, or to the person who does not find pleasure in solitary riding, the tricar offers many advantages, and, though decidedly more expensive to keep up than a motor bicycle, entails only very modest bills in comparison with those which affect many owners of cars.

The development of the motor cycle has been hastened and fostered by frequent speed and reliability contests, in which the nimble little motor has acquitted itself wonderfully. A hill a mile long, with very steep gradients, has been ascended in considerably less than two minutes by a 3 1 / 4 h.p. motor. We read of motor cycles travelling from Land's End to John-o'-Groats; from Calcutta to Bombay; from Sydney to Melbourne; from Paris to Rome—all in phenomenal times considering the physical difficulties of the various routes. Such tests prove the endurance of the motor cycle, and pave the way to its use in more profitable employments. Volunteer cycling corps often include a motor or two, which in active service would be most valuable for scouting purposes, especially if powerful enough to tow a light machine-gun. Commercial travellers, fitting a box to the front of a tricar, are able to scour the country quickly and inexpensively in quest of orders for the firms they represent. The police find the motor helpful for patrolling the roads. On the Continent, and especially in Germany, town and country postmen collect and deliver parcels and letters with the aid of the petrol-driven tricycle, and thereby save much time, while improving the service. Before long, "Hark 'tis the twanging horn" will once again herald the postman's approach in a thousand rural districts, but the horn will not hang from the belt of a horseman, such as the poet Cowper describes, but will be secured to the handle-bars of a neat tricar. Thus history repeats itself.

That the motor cycle is still far from perfect almost goes without saying; but every year sees a decided advance in its design and efficiency. The messy, troublesome accumulator will eventually give way to a neat little dynamo, which is driven by the engine and creates current for exploding the cylinder charges as the machine travels. When the cycle is at rest there would then be no fear of electricity leaking away through some secret "short circuit," since the current ceases with the need for it, but starts again when its presence is required. The proper cooling of the cylinders has been made an easier matter than formerly by the introduction of fans which direct a stream of cold air on to the cylinder head. Professor H. L. Callendar has shown in a series of experiments that a fan, which absorbs only 2 to 3 per cent. of an engine's power, will increase the engine's efficiency immensely when a low gear is being used for hill climbing, and the rate of motion through the air has fallen below that requisite to carry off the surplus heat of the motor. If an engine maintains a good working temperature when it progresses through space two feet for every explosion, it would overheat if the amount of progression were, through the medium of a change-gear attachment, reduced to one foot, a change which would be advisable on a steep hill. The fan then supplies the deficiency by imitating the natural rush of air. As Professor Callendar says: "The most important point for the motor cyclist is to secure the maximum of power with the minimum of weight. With this object, the first essentials are a variable speed gear of wide range, and some efficient method of cooling to prevent overheating at low gears.... It is unscientific to double the weight and power of the machine in order to climb a few hills, when the same result can be secured with a variable gear. It is unnecessary to resort to the weight and complication of water cooling when a light fan will do all that is required."

Thus, with the aid of a fan and a gear which will give at least two speeds, the motor cyclist can, with an engine of 2 h.p., climb almost any hill, even without resorting to the help of the pedals. His motion is therefore practically continuous. To be comfortable, he desires immunity from the vibration which quick movement over any but first-class roads sets up in the machine, especially in its forward parts. Several successful spring forks and pneumatic devices have been invented to combat the vibration bogy; and these, in conjunction with a spring pillar for the saddle, which can itself be made most resilient, relieve the rider almost entirely of the jolting which at the end of a long day's ride is apt to induce a feeling of exhaustion. The motor tricycle, which once had a rather bad name for its rough treatment of the nerves, is also now furnished with springs to all wheels, and approximates to the car in the smoothness of its progression.

Assuming, then, that we have motor vehicles so light as to be very manageable, sufficiently powerful to climb severe gradients, reliable, comfortable to ride, and economical in their consumption of fuel and oil, we are able to foresee that they will modify the conditions of social existence. The ordinary pedal-driven cycle has made it possible for the worker to live much further from his work than formerly. "To-morrow, with a motor bicycle, his home may be fifteen miles away, and those extra miles will make a great difference in rent, and in the health of his family. In fact, it almost promises to reconcile the Garden City ideal with the industrial conditions of to-day, by enabling a man to work in the town, and have his home in the country. This advantage applies, of course, less to London than to other great cities, on account of the seemingly endless miles of streets to be traversed before the country is reached. In most manufacturing centres, however, the motoring workman could get to his cottage home by a journey of a few miles. Even in London, moreover, this disadvantage will be overcome to a large extent in the future, for it is as certain as anything of the kind can be that we must ultimately have special highways, smooth, dustless, reserved for motor traffic, leading out of London in the principal directions.... My own conviction is that motor cycling, the simplest, the quickest, the cheapest independent locomotion that has ever been known, is destined to enjoy enormous development. I believe that within a few years the motor bicycle and tricycle will be sold by hundreds of thousands, and that many of the social and industrial conditions of our time will be greatly and beneficially affected by them."[13]