| Show RECENT BECENT DISCOVERIES Note Those papers on practical mi science ence estee have been prepared for The Her Heralds aids Home Study Stud Circle by Professor William J 1 of ot Drexel institute Wireless Telegraphy The idea of sending messages from one Point to another without the use of or connecting wires s has always been fascinating since the first practical tel teN telegraph It rt can n be accomplished in a variety of ways but all alt methods fall naturally Into two classes cla ses The first includes all those methods in which the transmission trans of tile the signal is effected by leakage of electric I current from the transmitting apparatus to the re ye end through the earth or the water The second class s methods in which the transmission tr ia Is 1 by waves traveling through the remar able atner etner which is conceived to t ill 1111 all aU space just as those waves travel which produce the sensation of light I i In any an method soothed yet known wires must be used at both the transmitting and the receiving end so ao that there is it no telegraphy yet which is absolutely i wireless Wireless telegraphy as now new I understood however employs no line wires such as are necessary in ordinary telegraphy to connect the transmitter r rand and the receiver Transmission through the earth or water without wires has be been n Ia Iaia ia iap t S p tf R RI I 1 JS Z tr i il l i The Leakage pU pUshed h 1 many many times time imf The earth Is full fun f I of wandering currents which w need only I Ia a sensitive detector like the telephone tele one to become evident Indeed the difficulty I I Is to prevent any uny currents currants which have luwe I access to earth from fram wandering and to toke I ke keep p them in the paths path marked out for I I Ithem thorn them Without enumerating the attempts which have been made mude in this direction dire I during the last half century or more morea moreR a R single example will be sufficient to tomaKe tom maKe maine m i e the t e matter clear cle r Some years rears ago Trowbridge bridge found that the time Ume Umes signals s from a clock in n the observatory i I in Cambridge could be distinguished four miles from the th line lIn conveying the signals o 0 Boston A telephone receiver was used use as a detector in a line Une about I fifty net feet long the th ends n s of the line I being grounded by b moons moans of rods i were stuck Into the earth The current I had bad spread out to this extent ent between cS the earth plates plat in Cambridge and Bop Bos Boston Bas Basto ton to assisted probably by the water mains and the water wate in the soil On this principle prin It was proposed that ships at sea should communicate a i strong current currant from a dynamo being sent into the sea flea through a trailing trilling wire and the current detected by a telephone connected to a similar wire trailing trilling from another ship It was even evenI suggested that communication could be he e established across the Atlantic by I sending a strong current through a wire the length of ol the Ameri Amer American can continent and connecting the ends of ot the line to the ocean A it telephone line running from England to Liberia would w uld pick up enough current to make maie m e ethe the sIgnals distinguishable To understand the operation ol of the second method it will be best beit to con consider consider sider alder tha the action of waves of a IJ similar character When a wave progresses over OYer the sur surface surface surface face of ot o water it is not by the hit onward motion of the water itself Each par tide Ucle of water oscillates up communicating its motion to the next and in Iii this way causing cauling the wave form to travel onward until it breaks upon the shore or gr is smothered out by the e friction in the water itself In Jn just this t ls way a wave passes fes over a fled fied of stand standing standIng standIng ing grain stalk keeps ke ps its place but the wave form moves moes onward A wave may mey be made to travel a fL rope or ora ora ora a long spiral spring in fact in any substance which for any my reason tends to resume its original shape sape or volume A wave wae In air is of much the same annie character although tho the motion of the air particles in ia to and fro along the direction or motion of tho the wave instead of across it for air has elasticity of volume but not of shape These air clr waves are ordinarily invisible but produce the effect of Q sound within certain limits of rapidity if I the receiver Is 15 an organ of hearing A single sharp disturbance of the air like an explosion starts farts an all air wave which travels outward in all directions from the source or a regular repetition repetition repetition tion of oC impulses like hike the sound S und of oC a siren whistle or of a bell beil causes a se so series serles ries rles of or waves These disturbances are transformed by the ear upon which the I wave strikes s into the sensation lon of the t r note of the bell reduced in loudness in accordance with the distance For the wave is in spreading out into greater and greater spheres and the proportion of ot the whole wave which Is received is 15 correspondingly reduced as aa it recedes I from the starting point If instead of oC falling upon an ear i which responds to a wide range of vi vibrations vibrations 1 i the tho waves are received by some apparatus which responds to but butone butone butone one definite PItch or rapidity of or vibration tion Uon little or ar r no effect is produced unless the waves are of o the saBle sarce pitch as that of ot the receiving instrument In ment Such an instrument is called a rose rem resonator nato and rind the action Is known as sym cym sympathetic pathetic resonating r or ac an action action antion tion The resonator reS selects only the waves of its natural period To account for the known phoneme phenomenon non of oC light it has ha been found round necessary nary sary to assume the existence of ot an all ill pervading substance called the ether Nobody can see e or feel el th ether but I there th are few If any now poW who doubt existence nce It I must be endowed with very v remarkable properties a rigidity I great enough to transmit waves with ith a velocity of 18 miles mUes a second a lightness lightners so ao inconceivable that all forms farina of matter pass through it with little HUle or orno orno orno no resistance filling filing all space even elen that between the c of ot every everybody ever body bod In Jn the ether are passing at all times and always with this immense speed of miles a second waves Of t all frequencies nUll and of or all lengths Tile The e H in ing waves wavea lie within comparatively narrow limits from about to about to the inch Shorter than these are the ultraviolet waves which affect photographic plates strongly vibrating about times a second and the X rays ras nobody knows how many billions i of times a second se Beyond the visible is ble rays at the other end the waves of or 10 to vibrations a second produce the effect chiefly of heat heal and still lower In n the scale seale comes waves of all aU frequencies fr down to toa toa toa a comparatively few thousands a see sec second ec ond and and of all lengths from a quarter of an inch to many miles mUes The effects of these long waves ayes are chiefly electric electrical al so far as yet known and they are generally gene UY called Hartigan waves from fromi i the name nOme of theman who first Invent investigated Investigated I I gated them systematically All ll 11 other waves naves however are of the th same sam general electromagnetic ele charac character ter and cur classification into and Roentgen rays ras light dark heat is only an evidence of or our limitations in receiving apparatus With new ne meth methods methods ads of receiving and detecting such I waves new effects may ay be produced |
