WIRELESS TELEGAPHY.

Marlborough Express, Volume XXXVII, Issue 169, 18 July 1903, Page 6 (Supplement)

WIRELESS TELEGAPHY.

Es«at, lead at a reoenfe meeting of the Blenheim Mutual Imprortmeat Society. [BY ft. M. BPBNOB.] It has been said that the nineteenth century was the century of inventions. So many were they that it would take volumes to enumerate them..! AmoDg the more- important may be : mentioned the discovery and applica- i tion cf steam power, and the uses of eleotricity in all its branches, of which uot the least important is Wireless Telegraphy. It has always been ihe object of man to get news of his fellow man as quickly as possible, and to this end he has used many devices. Lighted \ fires, waved flags, swift messengers, j and in later years, the electric telegraph, have been used as the, mediums by which previously arranged signals have conveyed messages. N>w, however, it has been discovered by eminent ecientists^that disturbances in^te"6tfeeT~caused by eksirici ty 'may convey messages from one point to another. This, how-I ever, is not the only form of VVirele^s j Telegraphy, for some uietbo^ of convtying messages over great distances is known by Eastern people. To give an instance; on the day on which General Gordon was murdered at Khartoum, a city one thousand miles from Cairo, the fact was known and taked of by the natives at the latter plaCf a quarter of an hour after th« event happened. Other instances of thig power, which is jealously guarded by the natives, might be cited. ' It is probably a highly trained mental effort of which Western civilisation is ignorant. The subject to be disoussed here is Wireless Telegraphy as we know it. Pi rmeating all space and through all matter (including gases) is a. colourless, odourless, inconceivably rarified something which we call ether. It should be understood that this ether is not a chemical and baa nothing to do with the liquid sold by a chemist, but exists even in what we call a vacuum. Just as our ideas of the solidity of wood aluminium, etc., underwent a complete obange with the discovery of the X Rays, so must our ideas of the solidity of everything -change to appreciate the term Wireless Telegraphy. The ether conveys certain waves to us which we call light, others called heat .and others again called eleclri city. These' waves cannot bi conveyed by air, for whereas air waves have the frequency of sometimes many thousands of vibrations per second, ether waves have the frtquency of many millions, billions and even trillions. Although there is so njuch d fl>renoe between the speed of air and etheric waves, there is a certain similarity in their behaviour, and so we may use air waves to illustrate tbe law at sympathy or " pyntony" as applied to Wireless Telegraphic apparatus. If a violin be tuned to a piano and th« loud pedal of the latter be put down, a nofe playtd on the violin will cauß9 the samo note on the piano to respond. Again, if a tuning fork be struok and htld near ano her of tbe same pitch which is silent, the silent one will take up the note. These vibrations are of course in the air, while electric vibrations are in the ether. Now the whole secrecy of tho wireless system lies in the power of tuning tbe transmitting aud receiving apparatus, so tbafe the message t-ent by a certain transmitter can be rec^ivtd by a certain receiver and no other. Signor Marconi aud 1 Dr. Oliver Lodge are doing their best to bring tbe tuning of the instruments to such a pitch of peifection, that it will be only one chance in a ! million that anot er person c>uld receive a message if he did not know ' the pitch of the transmitter. Before proceeding further it might be well to glance at the life of one who sacrificed his all for the advancement of science, namely James BowI man Lindsay. This humble sciential!, who was very poor, denied himself food, clothes, and comfort to buy materials to make his apparatus. He was a great student, although tbe son of a weaver, and went through his Arts course at St. Andrews, paying h»s fees with what he parnpd in tbe college recess. In 1885 he life up bis room with electric light of his own installation. He also bad a method of Wirpless Telegraphy of his own in ! which water inskad of ethar was the conducting medium, and with which he tflf-grapbed two miles. Besides this he made an induction cil four and a half feet long and containing five miles of wire. , Although Lindsay was tbe first to accomplish Wirf-less Telegraphy, there bave been since his day many eminent scientists who hare performed experiments in the same direction. For instance, Professor Ernest Rutherford, an old Marlborough boy, now at Montreal, sent mpseages through tbe ether over thp space of half mile in Cambridge in 1896, flltbough there were several Mone buildings in tbe way. Dr Oliver Ledge, another very prominent scientist, has been working for years to" produce a Wireless system which is somewhat different from Marconi's.

Mr Preeee, F.R.S., has a system very different from any of the others, hut which is never likely to attain to ;he fame high results.

Rhigi, an Italian, is a noted authority on Hertz waves and was

Marconi's teacher an 3 friend in Italy before Marooni came to England.

Dr. Hertz, who died at Ibo early age of 87, achieved such great things in aketricftl science that ii is certain seieace lost one of its most learned students and discoverers in him. Niehola Tesla and Professor Sylvanus Thompson are also noted workers in tlae interests of Wireless Telegraphy.

But to return to the subject; there are two kinds of electricity, dynamic aud static. Dynamic electricity is said to flow, guided by a conductor ; static is that which charges a material or surface capable of receiving it. Mr Preeee, General Manager of English Telegiapha, used dynamic in his experiments while Hertz used static, his waves being of perhaps 230,000,000 vibrations to the second, although another scientist produced I the same wavt-s at the comparatively ! small rate of 800,000 per second, but \ then they were each one-fifth miie long. . • i If two pieces of metal, one being charged with positive static electricity and the other with negative, (for jM&Si.ff^^Sseiif-w'TjfeljrJlS ttftfiese" two) be brought close together a spark passes between them. This spark acts like a stone thrown into a { Sill pond, for waves starting from it go on expanding, making larger and larger circles and therefore becoming weaker and weaker. If some of these waves called "Herts" waves, after the famous Dr Hertz who discovered them, can be brought into contact with Branley s coherer they can be made use of to make signals.

Herts waves may be detected In the following manner: a piece of wire bent in the shape of a hoop and having a knob at each end, is held by a thread of silk ; an electric spark is made some distance away and at once a small spark passes between the two knobs of the hoop. This proves that waves must pass between the spark and the cut hoop.

To show that the waves are not interrupted by the earth the following experiment was performed On the surface of the ground in Cornwall aa equilateral triangle of f mile side was made in wire ; 860 feet below in the mine another triangle was constructed exactly underneath and parallel to the first. A current being set up m the top triangle a 3park passed between the ends of the bottom one.

Having described the action of the Hertz waves, something ought now to be said about the apparatus for sending and receiving the " Marconigrams'' as they are sometimes called, but " ethergrams" as we prefer to call them for though Marconi gets the honour from the general public of having invented Wireless Telegraphy, the fact is that he, seeing great possibilities in the system from a business man's point of view, adopted Branley's coherer and Rbigi's transmitter, vastly improved them, made some additions and set off with hia instruments for England. Mr Preeee took a great interest in Marconi from the firot and put at-his disposal the best that the Telegraphic Department could give, which was a great advantage to him.

To create the waves a powerful spark must be produced. A. strong current is passed through an induction coil and a brilliant spark is made to play between two highly polished brass knobs. Ah long as it lasts it is sending Qut Hertz waves at the rate of about 230,000,000 per second and which travel 186,000 miles in the same time. These waves are each iv the shape of an enormous ball having the'spark as its centre, so that a man in a balloon directly above, and a man in a miue below, and a man anywhere round the oompuss could receive the same ruessuge provided they had the proper instruments. Now, if this spark can be made very powerful and its effect spread over a good length of wire, very strong waves can be made to be felt at a great distance, for "the more powerful the spark the stronger ihe waves.

The induction coil which creates the spark is constructed in the following manner: Double cotton covered copper wire of medium thickness (No 20 or 24) is wound hundreds of timea round a core of soft iron wires, outside the copper wire a thick layer of gutta-percha or some other nonconductor is pkctd; single silk covered copper wire of the thickness of horse hair is wound thousands of times round this. Between each row of the very fine wire paraffin paper is pasted to insulate it from the next row, otherwise there might be a short oircuit.

When a current of dynamic electricity is passed through the coarser wire, called the primary coil, the eoffc iron core becomes a temporary magnet and a current of static eleetrieity is induced in the fine wire or secondary coil, the ends of which are fastened to the brass knobs. One knob is charged with positive and the other with negative static electricity, and as negative and positive have always a great desire to unite, they do so here and so cause a spark. Tho eleatric current is brokeu and connected by a Morse key in order to send the dots and dashes of the message.

Let us now look at the receiving apparatus. The very crux of (he system lies in an insignificant little glass tube, the coherer. It is" composed of a little glass tube the thickness of a lead pencil and 2£ or 3 inches long. Inside are two silver plugs, fitting it exactly and onesixteenth inch apart. This ono-six-teenth inch space is partly filled with nickel and silver filings, mixed in the proportion of 96 per cent of the former to 4 per cent of the latter with the merest trace of mercury.

Now", filings are bad conductors of electricity when lodie,. but 'Hertz wavta hare the power of making them aohere or stick togethar. When eobtred tbej form a good conductor, and therefore the current which has been unable to flow because of this one sixteenth inch space, is able to pass over this bridge of filingg and work the Morse receiver. When the Hertz waves cease to come through the ettur an eleebric tapper shakes up the filings and they decohere so that the current is broken. Some of the Hertz waves which travelled through the ether strike the wire suspended from a kite, travel down, pass through the coherer and cohere the filings. If a long series of waves comas we call it a dash, if a short one we call it a dot and so by the Morse alphabet the words are spelt out. *

There are various methods of decohering or separating the filings. Clock - work tappers, revolving coherers, trembling boards arid vibrations made by all kinds of automatic j3j2.ut.rivan.pes arG'bolbg resorted loHby different scientists. Tbe tuning of instruments has already been referred to, but is too lengthy and complex a subject to discuss here. Suffice it to say that the whole secrecy of Wireless Telegraphy depends on the nicety of the tuning; To increase the secrecy of the messages, the pitch of the instruments may be changed daily, or other instruments may be used, so that i£ the pitch were discovered ooe day it would be useless the next.

Wireless Telegraphy through the ether is not the only known method, for it has already been stated that Lindsay had a method in which water was the conducting medium, while another scientist has used the earth, and yet another tha upper layers of the air.

As to the uses of Wireless Telegraphy besides its commercial value and cheapness, it Trill be simply invaluable for lighthouses, lightships, and ships in distress to communicate with the shore, and for besieged fortresses to use instead of the heliograph. It is being used instead of the field telegraph in the present Somaliland campaign and it will probably come into universal use for war purposes ere long.

There will now bs no need of great engineering feats to throw wires across vast deserts, rugged mountains and rushing torrents —for they are already spanned .by the ether. Ordinary telegraph or cable cum munication may be interrupted by gales, cyclones, and storms, but as the ether is in and through everything, the atmosphere and its disturbances included, these do not make tbe slightest difference to Wireless communication; and it is doubtful if even a thunder-storm would make any differenoe.

It is natural that Cable Companies should try to make out that Wireless Telegraphy is a failure, but nevertheless that does not alter the feet that it will be the sjstem of the future when (lie instruments are perfected and the marvellous rapidity of 200 words a minute is attained instead of the Cable Companies' 35, as Marconi promises it will be.

Who ft hundred years ago would have dreamt that ono conbineni could communicate with anothtr

over 8000 miles of space ? Who would have thuughfc that there would be -this invisible link to bind nations

logetherrand make all men brothers t k man who* prophesied such things then would have been accounted at mad, and yet hert we are to-day able to hold intercourse with our friends on another continent through thousands of miles of empty space. Truly Nature's secrets are being revealed one by one and what is coming, who can tell ?