When the transatlantic achievement was announced at the end of 1901, there was a tendency in some quarters to decry the whole system. The critics laid their fingers on two weak points.
In the first place, they said, the speed at which the messages could be transmitted was too slow to insure that the system would pay. Mr. Marconi replied that there had been a time when one word per minute was considered a good working rate across the Atlantic cable; whereas he had already sent twenty-two words per minute over very long distances. A further increase of speed was only a matter of time.
The second objection raised centred on the lack of secrecy resulting from signals being let loose into space to strike any instrument within their range; and also on the confusion that must arise when the ether was traversed by many sets of electric waves.
The young Italian inventor had been throughout his experiments aware of these defects and sought means to remedy them. In his earliest attempts we find him using parabolic metal screens to project his waves in any required direction and prevent their going in any other. He also employed strips of metal in conjunction with the coherer, the strips or “wings” being of such a size as to respond most readily to waves of a certain length.
The electric oscillations coming from the aērial wires carried on poles, kites, &c., were of great power, but their energy dispersed very quickly into space in a series of rapidly diminishing vibrations. This fact made them affect to a greater or less degree any receiver they might encounter on their wanderings. If you go into a room where there is a piano and make a loud noise near the instrument a jangle of notes results. But if you take a tuning-fork and after striking it place it near the strings, only one string will respond, i.e. that of the same pitch as the fork.
What is required in wireless telegraphy is a system corresponding to the use of the tuning-fork. Unfortunately, it has been discovered that the syntony or tuning of transmitter and receiver reduces the distance over which they are effective. An electric “noise” is more far-reaching than an electric “note.”
Mr. Marconi has, however, made considerable advances towards combining the sympathy and secrecy of the tuning system with the power of the “noise” system. By means of delicately adjusted “wings” and coils he has brought it about that a series of waves having small individual strength, but great regularity, shall produce on the receiver a cumulative effect, storing, as it were, electricity on the surface of the receiver “wings” until it is of sufficient power to overcome the resistance of the coherer.
That tuned wireless telegraphy is, over moderate distances, at least as secret as that through wires (which can be tapped by induction) is evident from the fact that during the America Cup Yacht Races Mr. Marconi sent daily to the New York Herald messages of 4000 total words, and kept them private in spite of all efforts to intercept them. He claims to have as many as 250 “tunes”; and, indeed, there seems to be no limit to their number, so that the would-be “tapper” is in the position of a man trying to open a letter-lock of which he does not know the cipher-word. He may discover the right tune, but the chances are greatly against him. We may be certain that the rapid advance in wireless telegraphy will not proceed much further before syntonic messages can be transmitted over hundreds if not thousands of miles.
It is hardly necessary to dwell upon the great prospect that the new telegraphy opens to mankind. The advantages arising out of a ready means of communication, freed from the shackles of expensive connecting wires and cables are, in the main, obvious enough. We have only to imagine all the present network of wires replaced or supplemented by ether-waves, which will be able to act between points (e.g. ships and ships, ships and land, moving and fixed objects generally) which cannot be connected by metallic circuits.
Already ocean voyages are being shortened as regards the time during which passengers are out of contact with the doings of the world. The transatlantic journey has now a newsless period of but three days. Navies are being fitted out with instruments that may play as important a part as the big guns themselves in the next naval war. A great maritime nation like our own should be especially thankful that the day is not far distant when our great empire will be connected by invisible electric links that no enemy may discover and cut.