The first aeroplane made by the two brothers was a very simple one, as was the method adopted to balance the craft. There were two main planes made of long spreads of canvas arranged one above another, and on the lower plane the pilot lay. A little plane in front of the man was known as the ELEVATOR, and it could be moved up and down by the pilot; when the elevator was tilted up, the aeroplane ascended, when lowered, the machine descended.

At the back was a rudder, also under control of the pilot. The pilot"s feet, in a modern aeroplane, rest upon a bar working on a central swivel, and this moves the rudder. To turn to the left, the left foot is moved forward; to turn to the right the right foot.

But it was in the balancing control of their machine that the Wrights showed such great ingenuity. Running from the edges of the lower plane were some wires which met at a point where the pilot could control them. The edges of the plane were flexible; that is, they could be bent slightly either up or down, and this movement of the flexible plane is known as WING WARPING.

You know that when a cyclist is going round a curve his machine leans inwards. Perhaps some of you have seen motor races, such as those held at Brooklands; if so, you must have noticed that the track is banked very steeply at the corners, and when the motorist is going round these corners at, say, 80 miles an hour, his motor makes a considerable angle with the level ground, and looks as if it must topple over. The aeroplane acts in a similar manner, and, unless some means are taken to prevent it, it will turn over.

Let us now see how the pilot worked the "Wright" glider. Suppose the machine tilted down on one side, while in the air, the pilot would pull down, or warp, the edges of the planes on that side of the machine which was the lower. By an ingenious contrivance, when one side was warped down, the other was warped up, with the effect that the machine would be brought back into a horizontal position. (As we shall return to the subject of wing warping in a later chapter, we need not discuss it further here.)

It must not be imagined that as soon as the Wrights had constructed a glider fitted with this clever system of controlling mechanism they could fly when and where they liked. They had to practise for two or three years before they were satisfied with the results of their experiments: neglecting no detail, profiting by their failures, and moving logically from step to step. They never attempted an experiment rashly: there was always a reason for what they did. In fact, their success was due to systematic progress, achieved by wonderful perseverance.

But now, for a short time, we must leave the pioneer work of the Wright brothers, and turn to the invention of the petrol engine as applied to the motor car, an invention which was destined to have far-reaching results on the science of aviation.

CHAPTER XX. The Internal-combustion Engine

We have several times remarked upon the great handicap placed upon the pioneers of aviation by the absence of a light but powerful motor engine. The invention of the internal-combustion engine may be said to have revolutionized the science of flying; had it appeared a century ago, there is no reason to doubt that Sir George Cayley would have produced an aeroplane giving as good results as the machines which have appeared during the last five or six years.

The motor engine and the aeroplane are inseparably connected; one is as necessary to the other as clay is to the potter"s wheel, or coal to the blast-furnace. This being the case, it is well that we trace briefly the development of the engine during the last quarter of a century.

The original mechanical genius of the motoring industry was Gottlieb Daimler, the founder of the immense Daimler Motor Works of Coventry.

Perhaps nothing in the world of industry has made more rapid strides during the last twenty years than automobilism. In 1900 our road traction was carried on by means of horses; now, especially in the large cities, it is already more than half mechanical, and at the present rate of progress it bids fair to be soon entirely horseless.

About the year 1885 Daimler was experimenting with models of a small motor engine, and the following year he fitted one of his most successful models to a light wagonette. The results were so satisfactory, that in 1888 he took out a patent for an internal-combustion engine--as the motor engine is technically called--and the principle on which this engine was worked aroused great enthusiasm on the Continent.

Soon a young French engineer, named Leva.s.sor, began to experiment with models of motor engines, and in 1889 he obtained, with others, the Daimler rights to construct similar engines in France. From now on, French engineers began to give serious attention to the new engine, and soon great improvements were made in it. All this time Britain held aloof from the motor-car; indeed, many Britons scoffed at the idea of mechanically-propelled vehicles, saying that the time and money required for their development would be wasted.

During the years 1888-1900 strange reports of smooth-moving, horseless cars, frequently appearing in public in France, began to reach Britain, and people wondered if the French had stolen a march on us, and if there were anything in the new invention after all. Our engineers had just begun to grasp the immense possibilities of Daimler"s engine, but the Government gave them no encouragement.

At length the Hon. Evelyn Ellis, one of the first British motorists, introduced the "horseless carriage" into this country, and the following account of his early trips, which appeared in the Windsor and Eton Express of 27th July, 1895, may be interesting.

"If anyone cares to run over to Datchet, they will see the Hon. Evelyn Ellis, of Rosenau, careering round the roads, up hill and down dale, and without danger to life or limb, in his new motor carriage, which he brought over a short time ago from Paris.

"In appearance it is not unlike a four-wheeled dog-cart, except that the front part has a hood for use on long "driving" tours, in the event of wet weather; it will accommodate four persons, one of whom, on the seat behind, would, of course, be the "groom", a misnomer, perhaps, for carriage attendant. Under the front seat are receptacles, one for tools with which to repair damages, in the event of a breakdown on the road, and the other for a store of oil, petroleum, or naphtha in cans, from which to replenish the oil tank of the carriage on the journey, if it be a long one.

"Can it be easily driven? We cannot say that such a vehicle would be suitable for a lady, unless rubber-tyred wheels and other improvements are made to the carriage, for a grim grip of the steering handle and a keen eye are necessary for its safe guidance, more especially if the high road be rough. It never requires to be fed, and as it is, moreover, unsusceptible of fatigue, it is obviously the sort of vehicle that should soon achieve a widespread popularity in this country.

"It is a splendid hill climber, and, in fact, such a hill as that of Priest Hill (a pretty good test of its capabilities) shows that it climbs at a faster pace than a pedestrian can walk.

"A trip from Rosenau to Old Windsor, to the entrance of Beaumont College, up Priest Hill, descending the steep, rough, and treacherous hill on the opposite side by Woodside Farm, past the workhouse, through old Windsor, and back to Rosenau within an hour, amply demonstrated how perfectly under control this carriage is, while the sensation of being whirled rapidly along is decidedly pleasing."

Another pioneer of motorism was the Hon. C. S. Rolls, whose untimely death at Bournemouth in 1910, while taking part in the Bournemouth aviation meeting, was deeply deplored all over the country. Mr. Rolls made a tour of the country in a motor-car in 1895, with the double object of impressing people with the stupidity of the law with regard to locomotion, and of ill.u.s.trating the practical possibilities of the motor. You may know that Mr. Rolls was the first man to fly across the Channel, and back again to Dover, without once alighting.

CHAPTER XXI. The Internal-combustion Engine(Cont.)

I suppose many of my readers are quite familiar with the working of a steam-engine. Probably you have owned models of steam-engines right from your earliest youth, and there are few boys who do not know how the railway engine works.

But though you may be quite familiar with the mechanism of this engine, it does not follow that you know how the petrol engine works, for the two are highly dissimilar. It is well, therefore, that we include a short description of the internal-combustion engine such as is applied to motor-cars, for then we shall be able to understand the principles of the aeroplane engine.

At present petrol is the chief fuel used for the motor engine. Numerous experiments have been tried with other fuels, such as benzine, but petrol yields the best results.

Petrol is distilled from oil which comes from wells bored deep down in the ground in Pennsylvania, in the south of Russia, in Burma, and elsewhere. Also it is distilled in Scotland from oil shale, from which paraffin oil and wax and similar substances are produced. When the oil is brought to the surface it contains many impurities, and in its native form is unsuitable for motor engines. The crude oil is composed of a number of different kinds of oil; some being light and clear, others heavy and thick.

To purify the oil it is placed in a large metal vessel or "still". Steam is first pa.s.sed over the oil in the still, and this changes the lightest of the oils into vapours. These vapours are sent through a series of pipes surrounded with cold water, where they are cooled and become liquid again. Petrol is a mixture of these lighter products of the oil.

If petrol be placed in the air it readily turns into a vapour, and this vapour is extremely inflammable. For this reason petrol is always kept in sealed tins, and very large quant.i.ties are not allowed to be stored near large towns. The greatest care has to be exercised in the use of this "unsafe" spirit. For example, it is most dangerous to smoke when filling a tank with petrol, or to use the spirit near a naked light.

Many motor-cars have been set on fire through the petrol leaking out of the tank in which it is carried.

The tank which contains the petrol is placed under one of the seats of the motor-car, or at the rear; if in use on a motor-cycle it is arranged along the top bar of the frame, just in front of the driver. This tank is connected to the "carburettor", a little vessel having a small nozzle projecting upwards in its centre. The petrol trickles from the tank into the carburettor, and is kept at a constant level by means of a float which acts in a very similar way to the ballc.o.c.k of a water cistern.

The carburettor is connected to the cylinder of the engine by another pipe, and there is valve which is opened by the engine itself and is closed by a spring. By an ingenious contrivance the valve is opened when the piston moves out of the cylinder, and a vacuum is created behind it and in the carburettor. This carries a fine spray of petrol to be sucked up through the nozzle. Air is also sucked into the carburettor, and the mixture of air and petrol spray produces an inflammable vapour which is drawn straight into the cylinder of the engine.

As soon as the piston moves back, the inlet valve is automatically closed and the vapour is compressed into the top of the cylinder. This is exploded by an electric spark, which is pa.s.sed between two points inside the cylinder, and the force of the explosion drives the piston outwards again. On its return the "exhaust" or burnt gases are driven out through another valve, known as the "exhaust" valve.

Whether the engine has two, four, or six cylinders, the car is propelled in a similar way for all the pistons a.s.sist in turning one shaft, called the engine shaft, which runs along the centre of the car to the back axle.

The rapid explosions in the cylinder produce great heat, and the cylinders are kept cool by circulating water round them. When the water has become very hot it pa.s.ses through a number of pipes, called the "radiator", placed in front of the car; the cold air rushing between the coils cools the water, so that it can be used over and over again.

No water is needed for the engine of a motor cycle. You will notice that the cylinders are enclosed by wide rings of metal, and these rings are quite sufficient to radiate the heat as quickly as it is generated.

CHAPTER XXII. The Aeroplane Engine

We have seen that a very important part of the internal-combustion engine, as used on the motor-car, is the radiator, which prevents the engine from becoming overheated and thus ceasing to work. The higher the speed at which the engine runs the hotter does it become, and the greater the necessity for an efficient cooling apparatus.

But the motor on an aeroplane has to do much harder work than the motor used for driving the motor-car, while it maintains a much higher speed.

Thus there is an even greater tendency for it to become overheated; and the great problem which inventors of aeroplane engines have had to face is the construction of a light but powerful engine equipped with some apparatus for keeping it cool.

Many different forms of aeroplane engines have been invented during the last few years. Some inventors preferred the radiator system of cooling the engine, but the tank containing the water, and the radiator itself, added considerably to the weight of the motor, and this, of course, was a serious drawback to its employment.

But in 1909 there appeared a most ingeniously-constructed engine which was destined to take a very prominent part in the progress of aviation.

This was the famous "Gnome" engine, by means of which races almost innumerable have been won, and amazing records established.

We have already referred to the engine shaft of the motor-car, which is revolved by the pistons of the various fixed cylinders. In all aeroplane engines which had appeared before the Gnome the same principle of construction had been adopted; that is to say, the cylinders were fixed, and the engine shaft revolved.

But in the Gnome engine the reverse order of things takes place; the shaft is fixed, and the cylinders fly round it at a tremendous speed.

Thus the rapid whirl in the air keeps the engine cool, and c.u.mbersome tanks and unwieldy radiators can be dispensed with. This arrangement enabled the engine to be made very light and yet be of greater horse-power than that attained by previously-existing engines.

A further very important characteristic of the rotary-cylinder engine is that no flywheel is used; in a stationary engine it has been found necessary to have a fly-wheel in addition to the propeller. The rotary-cylinder engine acts as its own fly-wheel, thus again saving considerable weight.

The new engine astonished experts when they first examined it, and all sorts of disasters to it were predicted. It was of such revolutionary design that wiseacres shook their heads and said that any pilot who used it would be constantly in trouble with it. But during the last few years it has pa.s.sed from one triumph to another, commencing with a long-distance record established by Henri Farman at Rheims, in 1909. It has since been used with success by aviators all the world over. That in the Aerial Derby of 1913--which was flown over a course Of 94 miles around London--six of the eleven machines which took part in the race were fitted with Gnome engines, and victory was achieved by Mr. Gustav Hamel, who drove an 80-horse-power Gnome, is conclusive evidence of the high value of this engine in aviation.

CHAPTER XXIII. A Famous British Inventor of Aviation Engines