the earth, or, in other words, disturbances of those forces. They are
sent out through this magnetic field, and follow the earth’s
curvature, in the same way that tidal waves follow the ocean’s
surface. Everywhere about us there is a sea of what science calls the
ether, and the ether is constantly in a state of turmoil, because it
is the medium through which energy, radiating from the sun, is carried
to the earth and other planets. This energy is transmitted through the
free ether in waves, which are known as electromagnetic waves. It was
this fact that Professor Hertz discovered, and the waves are sometimes
called the Hertzian waves. Light is one variety of wave motion, and
heat another. The ether must be distinguished from the air, for
science means by it a medium which exists everywhere and is to be
regarded as permeating all space and all matter. The ether exists in a
vacuum, for, although all the air may have been withdrawn, an object
placed in a vacuum can still be seen from outside, and hence the wave
motions of light are traveling through a space devoid of air.
Professor Hertz proved in 1888 that a spark, or disruptive discharge
of electricity, caused electro-magnetic waves to radiate away in all
directions through the ether. The waves acted exactly like ripples
that radiate from a stone when it strikes the water. These Hertzian
waves were found to travel with the same velocity as light, and would
circle the world eight times in a second. As soon as the existence of
these waves was known many scientists began to consider whether they
could not be used for telegraphy. But the problem was a very difficult
one. The questions were how to transmit the energy to a distance, and
how to make a receiver that should be sensitive enough to be affected
by it.
Let us picture a body of still water with a twig floating upon its
surface. If a stone is thrown into the water ripples radiate in all
directions, these waves becoming weaker as the circles they form
become larger, or in other words as they grow more distant from the
point where the stone struck the water. When the waves reach the
floating twig they will move it, and when they cease the twig will be
motionless again. Should there be grasses or rocks protruding up from
the water the motion given to the twig by the waves would be lessened,
or distorted, or changed in many ways, depending on the intervening
object. Whether the waves will actually impart motion to the twig will
depend on the force by which these waves were started and upon the
lightness of the twig, or its sensitiveness to the ripples as they
radiate. If the water were disturbed by some other force than the
stone the twig would be moved by that other force, and the observer
could not tell from what direction the motion had come, or how it had
been caused. Applying this to wireless telegraphy one may say that a
device must be used that will send out waves of a certain length, and
that the receiver must be constructed so that it will respond only to
waves of the length sent by that transmitter.
There must therefore be accurate tuning of the two instruments. Let a
weight be fastened at the end of a spiral spring and then be struck.
The weight will oscillate at a uniform rate, or so many times a
minute. If this be held so that it strikes the water the movement of
the spring will create a certain number of waves a minute. If now a
second weight, attached to a second spring, be hung down into the
water, the waves caused by the first will reach the second, and if the
springs be alike the movements or oscillations will correspond. But if
the springs were not alike, or if, in other words, the two instruments
were not in tune, the wave motions would not be received and copied
accurately. Therefore in wireless telegraphy the instrument that is to
impart the motion to the electro-magnetic waves that fill the ether
must be tuned in accord with the instrument that is to receive the
motion of those waves.
The sending of the wireless message requires a source of production of
the electro-magnetic waves. This is obtained by what is known as
capacity, or in other words, the power that is possessed by any metal
surface to retain a charge of electricity, and by inductance, procured
when a constantly changing current is sent through a coil of wire.
This capacity and inductance must be adjusted to give exactly the same
frequency of motion to the waves, or the same oscillations, if the
receiver that is tuned to vibrate to those waves is to receive that
message accurately. The receiving station must have the means to
intercept the waves, and then transform them again into electrical
oscillations that shall correspond to those sent out from the
transmitting station.
As early as 1844 Samuel F. B. Morse had succeeded in telegraphing
without wires under the Susquehanna River, and in 1854 James Bowman
Lindsay, a Scotchman, had sent a message a distance of two miles
through water without wires. Sir William Henry Preece, by using an
induced current, had telegraphed several miles without a connecting
wire. But the discoveries made in regard to the Hertzian waves placed
the subject on a different footing, and the possibility of an actual
usable wireless telegraph was now looked at from a new view-point.
Professor Hertz had used a simple form of apparatus to obtain his free
ether waves. A loop of wire, with the ends almost touching each other,
had been his receiver, or detector. When he set his generator, or
instrument to create the oscillations, in operation, and held the
detector near it, he could see very minute electric sparks passing
between the ends of the loop of wire. This proved the existence of the
electro-magnetic waves.
In 1890 Professor Eduard Branly found that loose metallic filings
became good conductors of electricity when there were electric
oscillations at hand. He demonstrated this by placing the filings
between metal plugs in a glass tube, and connecting this in circuit
with a battery and electric indicator. Professor Oliver Lodge named
this device of Branly’s a “coherer,” and when he found that it was
more sensitive than the Hertz detector he combined it with the Hertz
oscillator. This was in 1894, and the combination of oscillator and
coherer actually formed the first real wireless set.
Wireless stations on shore are marked by very tall masts, which
support a single wire, or a set of wires, which are known as the
_antenna_. The antenna has electrical capacity, and when it is
connected with the other apparatus needful to produce the oscillations
it disturbs the earth’s magnetic field. For temporary service, as in
the case of military operations, the antenna is frequently attached to
captive balloons or kites, and so suspended high in air. On ships the
antenna is fastened to the masts. The step that led to this addition
was taken by Count Popoff in 1895, when he attached a vertical wire to
one side of the coherer of the receiver of Professor Lodge, and
connected the other side with the ground. He used this to learn the
approach of thunder-storms.
With a knowledge of electro-magnetic waves, with a high-power
oscillator, and a sensitive coherer, it remained for Marconi to
connect an antenna to the transmitter, and thus secure a wide and
practicable working field for the sending and receiving of his
messages. This he did in 1896, and it was this addition that made the
wireless telegraph of real use to men. Improvements in the transmitter
and receiver have constantly increased the power of the invention, and
have gradually allowed him to employ it over greater and greater
distances.
With Marconi’s successful demonstrations of wireless in England its
use at once began. The Trinity House installed a station at the
East Goodwin Lighthouse, which communicated with shore and proved of
the greatest value in preventing shipwrecks. The Marconi Wireless
Telegraph Company was organized in 1897, and made agreements to erect
coast stations for the Italian, Canadian, and Newfoundland
governments, and for Lloyd’s. The great shipping lines established
wireless stations on their vessels, and the antenna were soon to be
seen on points of vantage along every coast. On December 12, 1901,
Marconi in Newfoundland caught the message sent from Cornwall; on
January 19, 1903, President Roosevelt sent the first “official”
wireless message across the Atlantic to Edward VII, and in October,
1905, a message was sent from England across the mountains, valleys
and cities of Europe to the battle-ship _Renown_, stationed at the
entrance to the Suez Canal.
[Illustration: WIRELESS STATION IN NEW YORK CITY, SHOWING THE ANTENNA]
The system of operating wireless telegraphy is in some respects
similar to that of the ordinary telegraph. The Morse Code is largely
used in America, and a modification of it, called the Continental
Code, in Europe. When the wireless operator wishes to send a message
to another station he “listens in,” as it is called, by connecting his
receiving apparatus with the adjacent antenna and the ground. He has
the telephone receiver attached to his ears. Next he adjusts his
receiving circuits for a number of wave lengths. If he catches no
signals in his telephone receiver he understands that no messages are
being sent within his area. Then he “throws in” the transmitting
apparatus, which automatically disconnects the receiving end. He
gives the letters that stand for the station with which he wants to
communicate, and adds the letters of his own station. He does this a
number of times, to insure the other station picking up the call. Then
he “listens in,” and if he receives the clicks that show that the
other station has heard him he is ready to establish regular
telegraphic communication.
A number of distant stations may be sending messages simultaneously.
In that case the operator tunes his instrument, or in other words
adjusts his apparatus to suit the wave length of the station with
which he wishes to communicate. In this way he “tunes out” the other
messages, and receives only the one he wants. If, however, the
stations that are sending simultaneously happen to be situated near
together, as in the case of several vessels near a shore station, the
operator is often unable to do this “tuning out,” and must try to
catch the message he wishes by the sound of the “spark” of the
transmitting station, if he can in any way distinguish it from the
“sparks” of the other messages.
There are several ways of determining when the two circuits are in
tune. One is to insert a hot-wire current meter between the antenna
and the inductance, which indicates the strength of the oscillatory
current that has been established. A maximum reading can then be made
by manipulating the flexible connections, and this will show whether
the two circuits are in accord. The other method is by using a device
that indicates the wave length. This measures the frequency of one
circuit, and then the other circuit can be adjusted to give a
corresponding wave length. The larger the antenna the longer will be
the wave length and the greater the power of the apparatus. It is
usual to employ a short wave length for low-power, short-distance
equipments, and a long wave length for the high-power, long-distance
stations.
Wireless telegraphy has already proved itself of the greatest value on
the ocean. It has sent news of storms and wrecks across tossing seas
and brought rescue to scores of voyagers. Ships may now keep in
constant communication with their offices on shore. The great lines
send Marconigrams to each other in mid-ocean, and publish daily papers
giving the latest news of the whole world. Greater distances have so
far been covered over water than over land, but this branch of the
service is being rapidly developed, and it must prove in time of the
greatest value across deserts and wild countries, where a regular
telegraph service would be impracticable. In such a country as Alaska,
where there are constant heavy sleet and snow storms, the wireless
should prove invaluable.
The telegraph and cable companies did their best to ignore the claims
of the wireless systems, but they have been compelled to acknowledge
them at last. Rival companies have sprung up, using slightly different
varieties of apparatus. Each of the big companies that were ready to
compete with the Marconi Company by 1906, the German Telefunken
Company, the American National Electric Signaling Company, the
American De Forest Company, and the British Lodge-Muirhead Wireless
Syndicate, had certain peculiar advantages over the others. The laws
relating to the uses of wireless, and especially the rights of
governments to the sole use of the systems in case of war, are in a
confused condition, but eventually order must come from this chaos as
it did in the history of the telephone and telegraph.
Wireless has brought the possibility of communication between any two
individuals, no matter where they may be situated, within the realm of
fact. A severing of communication with any part of the world will be
impossible. Storms and earthquakes that destroy telegraph systems,
enemies that cut submarine cables, cannot prevent the sending of
Marconigrams. The African explorer and the Polar adventurer can each
talk with his countrymen. The use of this agency is still in its
earliest youth, but it has already done so much that it is impossible
to say to what a stature it may grow. It should cut down the rates for
using wire and cable systems, and ultimately place the means of
communicating directly with any one on land or sea within the reach of
every man. All the world’s information will be at the instant disposal
of whomsoever needs it, and all this is due to those electro-magnetic
waves that permeate the ether, waiting to be put into service at the
touch of man.
XVI
THE WRIGHTS AND THE AIRSHIP
Wilbur Wright 1867-
Orville Wright 1871-
Men have always wanted to be able to fly. So long as there have been
birds to watch, so long have men of speculative minds wondered at the
secret of their flight. Early in recorded history men built ships to
sail across the seas, but the problem of air navigation has always
baffled them. The balloon came into being, but the balloon for years
was only a toy, dependent on the wind’s whim, and of the least
possible service to men. The problem of aerial navigation was to
master the currents of the air as the sailing-vessel and the steamship
had overcome the waves and tides at sea.
The history of invention often shows that some great thinker, or
school of thinkers, has stated a scientific conclusion that
generations of later men have never dared to question. The laws of
Aristotle in regard to falling bodies were never doubted until Galileo
began to wonder if they could be true. Sir Isaac Newton had stated,
and mathematical computations had proved his words, that a mechanical
flying-machine was an impossibility. Any such machine must be heavier
than the air it flew in. The weight of Newton’s authority and the
weight of figures were compelling facts, such as scientists had no
mind to doubt. But in spite of these facts men could see that birds
flew, although they were often a thousand times heavier than the air
they went through. And that sight kept men speculating, in spite of
all the figures and scientific dicta of the ages.
It was known for centuries that if a kite was held in position by a
string reaching to the ground the wind blowing against it would keep
it supported in the air. Now if the kite, instead of being stationary
in moving air, were to be moved constantly through quiet air it would
also stay up. The motive power might be supplied by a motor and
propellers, but in order to do away with the string which holds the
kite in position the aeroplane, which is only a big kite in principle,
must have some way of balancing itself so that it will stay in the
proper position in the air.
A German engineer, Otto Lilienthal, made a study of the mechanics of
birds’ flights, and determined to learn their secret by actual trial.
He built wings that were similar to those of the hawk and buzzard, the
great soaring birds, and in 1891 he began to throw himself from the
tops of hills, supported by these wings, and glided through the air
into the valleys. In this way he learned new laws of flight,
contradicting many theories of the scientists, and opening a new world
of speculation. But in August, 1896, his wings broke in a sudden gust
of wind, he fell fifty feet, and died of a broken back.
It was this problem of balancing that had cost Lilienthal his life. He
had tried to balance himself by throwing his weight quickly from side
to side as he held to his “gliding machine.” His pupil, Percy S.
Pilcher, an Englishman, continued his experiments, trying the same
method of balancing, but in September, 1899, his wings broke, and he
met the same fate as his teacher. It seemed that men could not shift
their weight quickly enough to meet the gusts of wind.
Meantime new theories of flight were being worked out in the United
States. Professor S. P. Langley, of the Smithsonian Institution, had
made experiments with plates of metal moved through the air at various
rates of speed and at different angles, and had published his new
conclusions in regard to the support the air would furnish
flying-planes in 1891. In 1896 he built a small steam-aeroplane that
flew a distance of three-quarters of a mile down the Potomac River.
And in the same year Octave Chanute, of Chicago, with the aid of A. M.
Herring, built a multiple-wing machine and tried it successfully on
the banks of Lake Michigan. But the problem of balancing was not yet
solved, and here Wilbur and Orville Wright entered upon the scene.
The Wrights’ home was in Dayton, Ohio, and there they had spent their
boyhood, in no way distinguished from their neighbors. Their father
had been a teacher, an editor, and a bishop of the United Brethren
Church. He had traveled a great deal, and was an unusually
well-educated man. Their mother had been to college. Their two older
brothers and their sister were college graduates, and the younger boys
would have had the same education had their mother not died and they
decided to stay at home and look after affairs for their father, who
was often away. In telling the story of their invention in _The
Century_ for September, 1908, they said, “Late in the autumn of 1878
our father came into the house one evening with some object concealed
in his hands and, before we could see what it was, tossed it into the
air. Instead of falling to the floor, as we expected, it flew across
the room and struck the ceiling, where it fluttered a while and
finally sank to the floor. It was a little toy known to scientists as
a helicoptere, but which we, with sublime disregard for science,
dubbed a ‘bat.’ ... It lasted only a short time, but its memory was
abiding.” At that time Wilbur was eleven and Orville seven years old.
These two brothers, scientifically minded, started a bicycle shop, and
bade fair to become ordinarily prosperous citizens of Dayton, much
like their neighbors. They were, however, deeply interested in news
from the world of science and invention, and when they read in 1896
that Lilienthal had been killed by a fall from his glider they began
to wonder what were the real difficulties that must be overcome in
flying. Further reading awakened a deep interest in the problem of the
airship, and they worked upon it, at first as a scientific pastime,
but soon in all seriousness. They built models in their workshop, and
experimented with them. Then, in 1900, Wilbur wrote to his father that
he was going on a holiday to a place in North Carolina called Kitty
Hawk, to try a glider.
The Wrights realized in 1900 that the only problem to be solved was
that of equilibrium. Men had made aeroplanes that would support them
in motion, and also engines that were light enough to drive the planes
and carry their own weight and that of the aviator. But when the wind
blew the aeroplane was as likely as not to capsize. Their study was
how to keep the machine from turning over.
The air does not blow in regular currents. Instead, near the earth, it
is continually tossing up and down, and often whirling about in rotary
masses. There is constant atmospheric turmoil, and the question is how
to maintain a balance in these currents that bear the machine. Put in
technical form it is how to make the centre of gravity coincide with
the centre of air-pressure.
The shifting of the air-currents means that the centre of air-pressure
moves. The aeroplane is sailed at a slight angle to the direction in
which it is heading, and the centre of air-pressure is on the forward
surfaces of the machine. The wind strikes the front, but rarely
touches the back of the plane, and so gains a great leverage that adds
materially to its power to overturn the machine. As the wind veers
continually it is easy to see the aviator’s difficulty in keeping
track of this centre of pressure.
Both Lilienthal and Chanute had tried to balance by shifting their
weight, but this was extremely exhausting, and often could not be done
in time to meet the changing currents. The Wrights realized that a
more automatic method of meeting these changes must be found, and they
worked it out by shifting the rudder and the surfaces of the airship
as it met the air-currents.
The earlier aviators had found that two planes, or “double-deckers,”
gave the best results. The Wrights adopted this type, believing that
it was the strongest form, and could be made more compact and be more
easily managed than the single plane, or the many-winged type. They
built their gliding-machine of cloth and spruce and steel wire. But
instead of the aviator hanging below the wings, as in the other
planes, he lay flat across the centre of the lower wing. A horizontal
rudder extended in front of the plane instead of behind it. This not
only guided the flight of the machine, but counterbalanced the changes
of the centre of air-pressure. To steer, the wings were moved by cords
controlled by the aviator’s body. They considered that the shiftings
of the air were too rapid to be followed by conscious thought, and so
their plan was to have a plane that would balance automatically, or by
reflex action, as a bicycle is balanced.
Langley had adopted wings that slanted upward from the point at which
they joined, copying the wings of a soaring buzzard. The Wrights
doubted whether this was the best form for shifting weather, and built
theirs more on the pattern of the gull’s wings, curving slightly at
the tips. They were made of cloth, arched over ribs to imitate the
curved surfaces of bird’s wings, and were fastened to two rectangular
wooden frames, fixed one above the other by braces of wood and wire.
Their next step was to try to find some method by which they might
keep their gliding-machine continuously in the air, so that they might
gain an automatic balance. The old method of launching the plane from
a hill gave little chance for a real test. Study taught them that
birds are really aeroplanes, and that buzzards and hawks and gulls
stay in the air by balancing on or sliding down rising currents of
air. They looked for a place where there should be winds of proper
strength to balance their machine for a considerable time as it slid
downward, and decided to make their experiments at Kitty Hawk, North
Carolina, on the stretch of sand-dunes that divided Albemarle Sound
from the Atlantic Ocean. They calculated that their gliding-machine,
with 165 square feet of surface, should be held up by a wind blowing
twenty-one miles an hour. The machine was to be raised like a kite,
with men holding ropes fastened to the end of each wing. When the
ropes were freed the aviator would glide slowly to the ground, having
time to test the principle of equilibrium. This plan would also do
away with the former need of carrying the plane up to the top of a
hill before each flight.
They found in practice that their plan of raising the plane like a
kite was impracticable, and that the wind was not strong enough to
support it at a proper angle. They had to glide from hills as others
had done, but they discovered that their theory of steering and
balancing by automatically shifting surfaces worked very much better
than the old method of shifting the aviator’s weight.