June 1, 1899.] 



KNOWLEDGE. 



137 



Btrations conducted with all that regularity and freedom 

 from failure which constitute the imperative condition in 

 order to be of public utility. 



In 18G6, Mr. S. A. Yarley discovered that certain metals 

 in powder cohere together when electrified wires act upon 

 them, a subject which was further developed by Mr. E. 

 Branly in 1890. Marconi produces his ether waves by 

 electric sparks passing between four brass balls, a device 

 of Prof. Righi, following up the classic researches of 

 Heinrich Hertz. A thin layer of nickel and silver dust, 

 mixed with a trace of mercury, is placed between two 

 knobs or electrodes fused into a glass tube. Ether waves 

 from a distant station cause this metallic dust to cohere 

 and so convert it into a conductor of the electric current, 

 which is conveyed to a Morse receiver, and so marks the 

 signals in ink on a travelling slip of paper. A hammer, 

 worked by an electro-magnet, is arranged so as to tap the 

 tube in order to shake loose the metallic dust and so break 

 the current between each stroke of the recording pen. 

 Metal conductors are so disposed in the instrument as to 

 admit of adjustment in order that only ether waves of a 

 certain kind may pass through. By this means a single 

 transmitter can work a number of receivers, provided they 

 are tuned by adjusting the conductor, as a tuning-fork 

 resounds to a certain note. 



For communicating over thirty, or even a hundred miles, 

 the entire outfit does not exceed more than one hundred 

 pounds in all, and, apart from the high flagstaff, the whole 

 apparatus can be arranged on a small kitchen table. 



Marconi's new instrument can be fixed upon a vessel 

 and influenced from a transmitting station on shore. A 

 ship fitted with a receiver may have an electric bell inside 

 it, which can be revolved so that only when pointing in the 

 direction of the transmitting station will the ether waves 

 operate on the bell. Thus, a ship in a fog will be able to 

 ascertain its bearings as accurately as with the compass. 

 For war purposes, the apparatus can be installed snugly 

 in the middle of the ship, out of reach of the enemy, and, 

 unlike flags, semaphores, or lamps, unseen by the foe. It 

 has been shown that, by means of parabolic reflectors, the 

 rays can be projected in any desired direction, and received 

 by a similar reilector, a feat which has been accomplished 

 by Marconi up to a distance of some two and a half miles ; 

 although the instrument fails to act if it is more than a 

 certain distance to the right or left of the centre line of the 

 beam, this part of the problem presents a promising field 

 for further investigation. 



Already successful installations of wireless telegraphy 

 have been worked between Alum Bay and Bournemouth, 

 fourteen miles ; Poole and Bournemouth, eighteen miles ; 

 signals have been regularly exchanged, and the experience 

 of fourteen months has proved that no kind of weather in 

 England could stop the working of the apparatus. Last 

 autumn an installation between theRoyalYachfOsborne," 

 and Osborne House, during the Prince of Wales' illness, 

 showed that as the yacht moved about in various portions 

 of the waters round the Isle of Wight, there need be no 

 doubt as to the possibility of telegraphing across long 

 stretches of land. The system has been in operation since 

 December between the South Foreland and the East 

 Goodwin Lightship, a distance of twelve miles, and during 

 the past month France and England have been successfully 

 connected. The English station is at the South Fore- 

 land Lighthouse, near Dover, and that of the French at 

 Wimereux, near Boulogne; messages were passed backwards 

 and forwards with the greatest ease, and the experiments 

 open up boundless possibilities for the application of wire- 

 less telegraphy in the everyday business of life. 



It is to the employment of the vertical conductor that 



Marconi attributes his success. A length of 150 feet of 

 copper wire is run up a flagstaft" to draw its message out of 

 space, and print down in dot and dash on the paper tape 

 the intelligence ferried across thirty miles of water by the 

 mysterious ether. Up to certain limits the distance to 

 which signals can be sent varies as the square of the height 

 of the flagstaff. A wire, twenty feet high, carries a signal 

 one mile ; forty feet high, four miles ; eighty feet, sixteen 

 miles ; one-hundred and sixty feet, sixty-four miles ; and 

 so on. The speed at which messages can be sent is equal 

 to that of the cable, from twelve to eighteen words a minute. 

 A remarkable circumstance is that simply by the appear- 

 ance of the dots and dashes recorded on the tape, Marconi 

 can teU which of the three operators at Boulogne is trans- 

 mitting a message, brought about by a difference in the 

 touch. " There is a distinctive handwriting about it." 



Sanguine as some are for the future of Marconi's system, 

 many eminent scientific men see nothing in it ; indeed, the 

 new acquisition is passing through the usual ordeal which 

 all great innovations have to endure. About seventy 

 millions of telegraphic messages are sent annually in this 

 country, while telephonic messages have reached not less 

 than four-hundred and fifty millions, but no one believed 

 such a result would ensue when the telephone system was 

 launched. Whatever may be the future of the system, 

 the late demonstrations inspire much hope for the speedy 

 development of another great scheme of international 

 communication, J. M. 



THE KARKINOKOSM, OR WORLD OF 

 CRUSTACEA.-IX. 



By the Rev. Thomas E. E. Stebbing, m.a., f.r.s., f.l.s., 

 F.Z.S., Author of "A History of Crustacea," "The 

 Xaturalist of Cumbrae," "Report on tlie Amphipoda 

 collected by H.M.S. ' Challenyer,' " etc. 



LA DIGNITE DU CHEZ-SOL 



THE ancient Egyptians were a wise and under- 

 standing people. But the system they adopted 

 of mummifying themselves and their cats only 

 showed an amiable weakness. It was a vain 

 attempt at thwarting that law of existence which 

 calls upon every conscientious vegetable and animal to 

 live and let live, or, in other words, to eat and be eaten. 

 Like all other creatures, the crustaceans are anxious to 

 prolong to the utmost limits the first part of this 

 alternative. Hence, though they don't care for embalming, 

 they have been driven to evolve or invent resources of 

 shelter and seclusion, that might otherwise seem 

 unnecessary for beings free to range or to repose in the soft 

 and roomy bosom of the ocean. 



Houses and clothes are not, like food, an original 

 necessity of animal life. They are an acquired taste, the 

 beginnings of luxury and civilization. Probably they were 

 adopted by man in the guise of fortress and armour before 

 they became the costly ministers of his comfort and vanity. 

 But, however the desire for a domicile may have arisen 

 among ourselves, the construction and use of a homestead 

 are no exclusive triumphs of human intelligence, although 

 the fettering of freedom thereby entailed, the rates and 

 taxes, the overcrowding and the drainage, may be all our 

 own. 



It must not be expected that marine invertebrates will 

 show any great advances in architectural skill. Of 

 crustaceans it may be said, that, whatever else their dwel- 

 lings are designed for, they are never designed for display. 

 But, simple as each dwelling viewed by itself may be, when 



