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SCIENCE UP TO DATE

WIRELESS TELEGRAPHY,

[By James Collier,]

CVI,

(Special Rights Secured by the ‘Star.’)

The first practical realisation of wireless telegraphy is not yet a score of years eld. «r.<l already it is one of the fences that determine. Tinman affairs. A rocrot message sent out from some nameless station in the South AUamh 1 reaches itsdestinatioii, and two unsuspecting British warships go to their doom. A .magnificent y. earner. on her maiden voyage m theNorth. Atlantic. Tushes headlong to destruction. but. hundreds of miles away, another steamer bears a fault appeal for aid, :;i;d speeds to the us-vv. With the headquarter* of her wireless system at the t’anaries. Germany long kept her predatory cruisers in the Atlantic and the Indian Deem; in constant 'oneh with her enemies sh.ns and warships. What is tins wonderful power that can thus wring its secrets fioni the ambient air. winch we believed to he dent. dumb, and blind':’ A tew words of histoiv must precede the answer. - -Pieli.mnary Experiments.It was remarked one e\ oiling at a Now Brighton Hotel, in : ....; t-;T a re, man} ve.iis ago, that the sound of the human voice carried readily for some distance up or down a narrow river or creek. Many vea;> ember, in RD2, Professor Morse.

American inventor <>f the eh-cti n telegraph. immvsfvd wat'-'t- into his service as a cornice lor of eiecuu-ry. He sent signals across Now Vork Harbor tor a mile, and messages ewer the canal at Washington, a, distance of 80ft, using huge copper plates at ea-.ii teiminus. Hut a powerful current was ivq nurd to ovccume the- resistance ul water, and tins made the adoption of the met bed, impracticable 1 . In that same year of 1842 Professor Joseph He my, one el the anticipators of the electric telegraph, made electric waves Hud their way from a top

loom in his home, through walls_ and Hocus, and down to wires stretched in his (cikvr. Ail unknowingly, ho had arrived el tho discovery that a- current- of high intensin' c.in induce a current- in a-noiher wire miles away. It was tho key to

*• wiroles-," but the lime eras not yet ripe, for applvingor cron fulily realising it. More than 40 year* passed away till in dticed rmr-nU- were brought into adnm. In ]oSS Kdiron. fhe ctrea-t inventor, kept the trains on a One in the Staten Island tailtv a v in constant r-.mmunication with a telegraph wire mi the tine. The invention was afterwards used on the Lehigh \ alley railway, hut was discontinued as not bents commercially profitable, dim wave- of discovert' passed to England. In 1896 Sir IV. ,I’recce. chief electrician to the Post Office, laid a cnl>!-" b-et ween Laveinock. in the Bristol Channel. and an island three rr four miles distant. As the cable often got, fouled by ships anchors, in 1898 Prccce had th» idea, of stmehiug wires along the opposite shores, a-nd lie then ascertained that an electric pulse sent- through, one wire wa.-. instantly peu-eived in a telephone attached to die it iter. But- each line had to be a.- 1 n: -is the distance between the two. and this requirement damn mB-d lines of an impracticable length. Between Mover and C-alais lilies at- least 22ft long would hay* been nccessat y. --St ienti tic Forerunners I; is just half a century eince James (4-ik. Maxw ell, one of the greatest physicists of our time, arrived at the conclusion, bv dint ol mere calculation, that eWtricitv and tight move with the fame vi lochy. .or at ■; .-peed of 186,400 miles a second, and ho predicted, n-s a consennence that thev would he found to l-e of the niiii" nature. He I.mutilated til,theory that electricity propagates itself, like light , in waves only in longer waves than light. Not- td! a quarter of a- century

la ter was ibe prediction fulfilled, in 1558 Heinrich Hertz. a brilli.vd. student of that great mas-t.-ri Helmholtz, furnished the proof. He showed that, where alternating currents i ■' high intensity are set up. the resultant f-m-rgy may be conveyed away in the form of eie.trie waves. He further experimentally proved tba-t these waves faove with the speed of light. In honor ef their di.- overer they were christened tiie Hertzian waves.- 'this was the first great discovery that made wireless telegraphy practicable. Nevertheless Hertz was not the first- to perceive that these waves might be thus utilised. Biz' (Uiver Lodge was one of the first, and a Hindu, Professor -Taga-iis (..'bunder Bose, so well -crown for other- discoveries, was the first to send a .signal by wireless telegraphy. Much, however, remained to be done. Founding on a discovery made in 1635 by Professor Onesti. of Fermo, Professor Braid v. of the fat hoik- ITiiversitv of Pa ris, devised a coherer (literally, a sticker-together-. i\v means of which the Hertzian waves, romping through space, are harnessed and made to carry messages, and the invention has been improved both By Lodge and Fessenden. Lodge further

contrived the decoherer. by means ef which ordinary Morse letters can he registered by the Hertzian waves. To Professor Eight, of Genoa, we owe the balloscillator. which made it possible to send out very powerful waves. Still another step towards wireless telegraphy was taken when Professor Putherford’s magnetic detector first made practicable the transmission of messages across the Atlantic.

An Abortive Attempt.—

Amid this crowd nt successes, it- appears hardly worth while to record a failure. So early as 1879 Professor D. K. Hughes

began a senes of experiments that might, have led turn to .Marconi's discovery 10 or 20 years before its time. Hughes invented a. microphone that a Horded an un-

equalled means of receiving wireless m?s

sages, which were carried by aerial electric waves shot, out by an electric spark, ri-- exhibited his appa-ratus to Sir G. G. Stokes, who could perceive nothing new in it. as another eminent physicist could tee nmhing in Sir W. Preece's wireless electrical experiments. Thus two of the greatest- physicists in England blocked the ways leading to a. similar discovery, .hist so did Sir IV. Thomson nearly suei ?rd in thwarting Abe attempt, soon to he gloriously successful. to harness the mighty force? of Niagara- and conduct them to Buffalo and a hundred other industrial . mitres.

—Marconi and IV.pnff.--Evidently it i? true that, as the hislinn '-1 the steam engine asserts, "great

and groat disco

varies sto s"ld<iui, the work of any one mind." We have followed the progress ni di'; ove!v atk: inveittio:i in respect oi wireless telegraphy. Nothing seemed left to be done, and yet something all-essential remained. The piHelically final step was still to taken, and it was taken simullaneotnhfe 8 t«y two inventors, residing respectively in the north-east ami the southwest o: Europe —the famous Russian Admiral Topoif and the Italian .Marconi. Tin* two systems, begun and wrought out independently, are said closely to resemble one another, ami they sum up all tin- piior discoveries and iuvcuuions.

'l iie Iherer

let si- hark luck to the coherer. So long ago a.s 1866 S. A. Varley found that v. h.-i, hi- hi ighteued the electric current, a loose hint of Uacklcad particles instantly t orupaeteil themselves into a- conducting bridge, which Varley adapted to form a lightning-conductor. Nineteen years later Liiiesci, of Frauo, showed that a mass of pow.i. re t ,-opoer becomes a conductor almost ri/ual to wire when an electric wav- heats cn it. Plaiting from this dis•■...very, Braniy. as above said, devised the coh-rer. as hir 0. Lodge happily te lined it. which not only receives, but positively seems to invite, electric waves. Hcsting on this invention and that discovery, Marconi perfected a coherer which, with a mixture of nickel filings, hard silver flings, and a trace of mercury, utters through a telegraph sounder or indents on a. moving strip of paper th© signals brought or sent by the Hertzian waves. The words record a simp]© fact, but it resembles nothing else in nature. Th© coherer stands absolutely alone. A glass tube Ij inches long and one-twelfth oi an inch in internal diameter, containing electrodes and a trifle of metallic dust, performs this miracle. Hertz generated elee-tedtt-jwßWfr-that bMß®w<l lof't* £«m.£ras:

to crest. The electric waves generated by Marconi are about 4ft long, and there, are 950 millions of them every second. They are 600 ft long, says another, referring; to a different dimension. They go straight through brick or stone walls, through roofs and floors, through promontories and mountains. They arc arrested only by metal. Hence the network of metal wires at each “wireless” station. —'Marconi's Poles. — It will bo remembered that at Sir W. Preece's wireless station the two opposite lines of wire had to he each as long as the distance between them. Marconi Inns incorporated the principle in Ids system. At each terminal ho sinks a tall mast and attaches to it a perpendicular wire, and the telegraph distance equals the square of the length of the suspended wire. A wire 20ft Jong commands a. mile of wireless telegraphy; if 40ft. then four miles ; and so on. So. at least, it was in the early days of wireless, hut, as we shall presently see, a simpler method was ultimately adopted. —Gradual Progress.—

In 1894 Marconi made- his first very modest- experiments with wireless telegraphy, and it is believed that he was the first to signal for more than a mile. He certainly was, it- is stated, the- first to telegraph for a, distance of eight or nine miles. lit was 'disbelieved and ridiculed, but he persevered, and, being aided by hereditary wealth and having youth tin his side (he- was only 20 years old when he began), he was at length greatly victorious; He next signalled from the Isle of Wight to Bournemouth, on the south coast of England, a distance of 17 miles. At the Kingstown regatta, in Ireland, held in duly, 1898, he reported to the shore, without a ■imiracnt’s Joss of lime, the. results of the races as seen from a steam yacht. In the same year he telegraphed wirelessly across ‘the English (Tiaiimd from Dover to Calais, a distaiuv commonly rated at 22 mile*. Ho next transmitted messages from Boulogne to the South Foreland .lighthouse, 52 miles away. .Similar messages were sent during the autumn manoeuvres of the .British fleets to a distance of 80 miles. And finally, at least on land by hint. Marconi .succeeded in signalling from the Isle of Wight to Land’s End, a- distance of ICO miles. Step by step, each longer than its predecessor, lie had come to this great result. - 1 hat last exploit was achieved in the spring of 1901, hut before the fateful year was out .Marconi’s crowning triumph was achieved. “At noon on .December

12 the 2.0C0 milt's ocean from Cornua!! to Newfoundland were spanned hy invisible infers.” The apparent result was infinitesimal. Only the three dots that- stand in the .Morse code for the letter S were faintly audible through a magnifying telephone receiver, but these three tiny marks or sounds were the prophets ami harbingers of many a. future signal. >OS. which would bring salvation and safety to the passengers and crew of mm*y a- sinking ship. After a short period of seven years, chequered by disappointment, vexations, and set-barks, but also glorified by striking; successes, one of the greatest inventions of modern times was brought to a consummation. There were still difficulties to be overcome. In order to intercept the electric waves coming- overhead .Marconi had launched a-

captive- balloon and sent up a. big tethered kite, hut like Job's legendary asses, both Jute and balloon had taken unto themselves wings and flown away. He nexttried suspending a wire in' the air to cat-eli the. ethereal undulations as they flashed by. It proved nnnccessarv. The high masts, equipped with long ‘vertical wires, were high, enough. The Hertzian v.avt-s appear to cleave to tin- surface o! the. globe, though between ('ornwall and Newfoundland t!m globe rites like a hill 110 ft high.

-—Kvee.—■

Mln-n til- news <.f this magnificent dis- < ovary reached the London" Block Lx-chan-e, the cdi.i res of all the cable e.om-pimi-’s fell alarmingly. “ ( allies might now i:, coiied up and .sold for junk." it was ii-dit-ved. fine panic was at least pir-maime. "Wireless" is still --low and somewhat um-citain. Ihe cable com pa i lies are still profitable and indispensable. Bui jest as surely ns electricity Is superseding other agencies, wireless telegraph v will in tone supersede telegraphy Be tide. "Mcanwhil ' it is eroding a field, of It- ~en, Ii I'kices new powers in the hand of a naval i.oiiinrindor. “ A touch on a- button in a flagship" will initiate every tactical evolution in a (Be 1 . The Mashing lantern b* night and lie l seinap.'ioie by day will disappear. Tin' steam r-h'-n in a fog and the gun signal are amiqi.a-ted. Tt- breaks new ground in the service uf commerce and trade, it hears tin- lighthouses spell their names, and thus guides the mariner. In the- crowded English or Irish Channels, or even in th" Atlantic lanes, it affords a priceless * entity against collision. --Imp; ovetnerits.—. The waves aie radiated in all directions, (Viiintiies widely separated may thus he bound together. Bat- cannot such messages Be read by anyone within the winking radius of tin transmittir.g instrument? They can: but- Si,.- Oliver Lodge ba,s obviated the danger by attuning a. transmitter and a receiver to the same note, so that only one iccciver shall respond to a par-

ticnkir set- of waves. Maivom has never erased to perfect- his invention, and he has taken out- sonic 150 patents. Put lie has left ir to men of science to discover lli.' .-.pertiting taws of these mysterious waves. I'h'ining and Ploclimnnri, I’iirpain and the late Poincare, and on the practical side Tis-ot, have, sought to probe them. Mawmi's developments have been carried out on she -tc of water on the sea. Slnhv. a.m! Aren. Praam and Gnarini have mad-' it piacii -able on land.

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Permanent link to this item

https://paperspast.natlib.govt.nz/newspapers/ESD19150106.2.91

Bibliographic details

SCIENCE UP TO DATE, Issue 15693, 6 January 1915

Word Count
2,341

SCIENCE UP TO DATE Issue 15693, 6 January 1915

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