MARCONI'S LATEST.

Daily Telegraph (Napier), Issue 9940, 11 December 1900, Page 7

MARCONI'S LATEST.

Privacy of Wireless Telegraphy Ensured.

No Need for High Poles.

A London' cablegram received a few days since reported a new discovery with regard to wireless telegraphy. This discovery was thus indicated by the Daily Mail on October 23 :— I am able to record to-day the most important advance in the practical application of wireless telegraphy. Of late years a great deal has been added to our knowledge of the vibrations of the ether, though much more remains to be iliscovered. Only a limited number of these vibrations —those known to us as lieht and radiant heat —are directly perceptible to our senses. To detect any other waves except those of light, which the eye perceives directly, science has had to discover indirect means. An electric eye is needed to detect the Hertzian waves, and it was through the improvements first made by Marconi in the method of picking up the wa%es in a delicate instrument known as the "coherer" that he made wireless telegraphy possible. The electric waves, which are quite different from electric currents in wires, are started by means of sparks from an induction coil. From one knob of the coil a wire goes to the earth ; from the other a wire ascends to the top of a high pole, where it is laid bare to the ether. Then, whenever the key of the sending instrument is depressed, a torrent of sparks crackles between the knobs of the induction coil, and from the bare wire at the top of the pole Hertzian waves are sent out in every direction. PICKING UP THE WAVES. At the receiving station a similar wire raised high in the air picks up the waves out of space and carries them to the "coherer." In principle the "coherer" is this: Between the ends of an interrupted wire from a small battery are placed some fine metal nlings. .Normally they oppose a complete resistance to the passage of the electric current. But when the Hertzian waves are conducted by the receiving wire to the tube in which they lie they form a bridge between the ends of the interrupted wire and allow the current to pas 3. This current in its turn actuates an ordinary telegraph relay which works a Morse receiver. When the Hertzian rays cease to fall upon the "coherer" a little tapper electrically worked breaks down the bridge of metal filings and leaves it ready to be affected by the next set of waves received from the distant sending station. In this way, by the aid of the familiar dots and dashes of the Morse system, messages are sent across space without wires. Simple as the process seems when described in its bare outlines, it was a stroke of genius to conceive it, and it has needed infinite patience and perseverance to perfect it in all its details. But Marconi has succeeded in overcoming all difficulties. When he first came to England with his invention in 1896 the distance to which messages could be sent w>«s only about two miles. Now messages can be sent from Chelmsfotd, in Eisex, to Wirnereux, in France, a distance of 85 miles over land and water. During the naval manoeuvres of 1898 Marconi maintained regular and perfectly effective communication between two battleships at a distance of 60 miles—that is to say, when the ships were invisible to each other below the horizon. : ' POST OFFICE OBSTRUCTION. If it had not been for the obstruction of the British Post Office the system would already have been in extensive use for signalling purposes all round our coasts. Several foreign Governments at c already contemplating its use in place of cables for connecting o'.itlying islands with the mainland or adjacent islands. It works over the present distance without ever failing, in storm and fog, in sunshine and rain. No other inventor has ever succeeded in communicating over more than a third of the distance which Marconi bridges every day. But scientists still pooh-pooh and rivals still sneer at his achievements. But at his experimental station at the entrance to Poole Harbor, Marconi has gone on quietly with his work, unheeding scientific pooh-poohs, and knowing well that the logic of facts would one day triumph. At one site in his workroom, with the tide racing out into the Channel just outside the windows, there is auditory proof of the one great disati vantage which ha-s hitherto ntood in the way of wireless telegraphy. The Admira'ty has adopted Marconi's system, and 32 ships and land s'ations are now being fitted with the instruments. In Portsmouth Harbor H.M.S. Hector already has the apparatus on hoard. In Portland Harbor, 65 land miles away, with the Purbeck Height in between, H.M.S. Minotaur is similarly provided. In the room at the mouth of Poole Harbor, tick-tick goes Mr Marconi's receiver, and the tape of the Alorse instrument rolls out its message of dots and dashes. It is an officer on board H.M.S. Hector speaking to his colleague on board H.M.S. Minotaur. THE LAST OBSTACLE SURMOUNTED. This was the disadvantage. Messages sent by Marconi's earlier instruments can be picked up by a suitable receiver anywhere within the radius of action of the sending apparatus, and unless they are in code, read at once. The raugnkude of this obstacle to the successful commercial use cf Marconi's system is obvious. Scpntists declared the obstacle to be insupsrable. Nevertheless Marconi has surmounted it. On the table is another receiver. It takes no messages except those sent from the experimental station at Sf. Catherine's Point in the Isle of Wight thirty miles away. Bγ if a aide is another sender. It despatches messages which can only be detected and spelt out by the conesponding receiver at St. Catherine's Point. Although the lines of communication cross each other the oilioer at Portsmouth and Portland can detect no trace of the meysages sent by Marconi to his assistant iv the Isle ot Wight. Still greater marvels follow. From the high pole outside the windows the single conducting wire is attached to two of the new receivers. The assistants at St. Catherine's then despatch two messages simultaneously. The little piece of baie wire at the top of the pole picks them both up rait of space, and each receiver disentangles its own message, and prints it on the tape undisturbed by the other. The two have come across space with the speed of light, in mutually intermingled electric waves. But there is no incoherence, no contusion. Three, four, half-a-dozen messaged can be sent at the same time, but no one of them can be picked up save by the receiver to which it is e.-pecially ditected. NO MORE HICK POLES. This new advance, the consequences of which are almost incalculable, is achieved by "tuning' , the transmitting and receiving instruments together, so that the Hertzian rays which are despatched from

a particular transmitter are ot such period of vibration and length of wave that they can only be picked up by the particular receiver to which they are adapted, and sines the possible variations are practically infinite, the chance of anyone getting hold of the message except by means of the receiver to which it is bent is n<l. Another important improvement whick Marconi has recently made enables him to dispense with the use of high poles. Messages can be sent and received by means of metal cylinders raised a few feet from the ground, and the whole apparatus can now be placed in a cart and moved about at will. The inventor smiles'at the enthusiasm with which his visitors receive the demonstration of these new wonders of wireless telegraphy. Modestly he ad--mits that they make a good deal of difference. "But I have been told," He says, " that though the result is new the means I employ are old." One more great advance has yet to be made, and when he is asked if he proposes to speak across the Atlantic and ruin the cable companies he smiles again. "Perhaps," he replies; "but, you , know, if I do I shall only be doing what everyone else could do if they knew how."