676 



THE STANDARD DICTIONARY OF FACTS 



current is passed through it, are the means by 

 which messages are recorded. The coil is at- 

 tached to a very light glass siphon in the shape 

 of an exceedingly fine capillary tube, through 

 which ink from a reservoir is drawn by electric 

 attraction, the reservoir and the moving paper 

 ribbon upon which the ink falls being oppositely 

 electrified. The extremity of the siphon is not 

 in contact with, but only very near, the paper. 

 When there is no current the ink traces a straight 

 line; when the current is passing the marks or 

 deviations constituting the letters are produced. 

 The delicacy and rapidity of this instrument are 

 even greater than those of the mirror galvanom- 

 eter, and the siphon recorder accordingly is 

 highly valued. About the year 1837 electric 

 telegraphs were first established as commercial 

 speculations in three different countries. Stein- 

 heirs system was carried out at Munich, Morse's 

 in America, and Wheatstone and Cooke's in Eng- 

 land. The first telegraphs ever constructed for 

 commercial use were laid down by Wheatstone 

 and Cooke on the London and Birmingham and 

 Great "Western Railways. The wires, which were 

 buried in the earth, were five in number, each 

 acting on a separate needle, but the expensive- 

 ness of this plan soon led to its being given up. 

 The single-needle and double-needle telegraphs 

 of the same inventors have been more exten- 

 sively used. Among recent improvements in 

 electric telegraphy the most important are those 

 by which a wire can be used for more than one 

 message at a time. In 1872, a workable method 

 of sending simultaneously two messages in op- 

 posite directions on the same line was intro- 

 duced, and it was also discovered that two mes- 

 sages could be sent in the same direction (duplex 

 telegraphy). The two plans being combined 

 formed quadruplex telegraphy, by which the 

 message-carrying powers of the wires have been 

 greatly multiplied. 



Wireless Telegraphy has made use of three dif- 

 ferent methods, which may be classed as con- 

 duction, induction, and wave methods. In the 

 first method currents are sent through the earth 

 from an electrode to another at the sending 

 station. By induction, use is made of the prop- 

 erty which alternating currents possess of ex- 

 citing similar currents in neighboring conductors, | 

 the aim being to get as intense current as possible 

 in the secondary circuit. Mr. W. H. Preece, 

 England, by combining the two has signaled 

 forty miles thus. The third method is by elec- 

 tro-magnetic waves which are detected by a 

 coherer a glass tube filled with metallic filings, 

 into the end of which the terminals of a relay 

 circuit enter, sent thereto by a transmitter. 

 The wave falls on other conductors, and, the 

 spark gap being replaced by a coherer, the relay 

 circuit is closed and a signal is made. Signor 

 Marconi, an English naturalized Italian, intro- 

 duced the latter method, by which he has sig- 

 naled across the Atlantic. To Marconi is gen- 

 erally ascribed the honor of inventing wireless 

 telegraphy, or the sending of telegraphic mes- 

 sages without the use of other medium than the 

 atmosphere. Trans-Atlantic passenger vessels 

 are now fitted out with wireless telegraphic appa- 

 ratus, by means of which almost constant com- 

 munication may be maintained between passing 



M-ls or either shore. Wireless telegraphy, 

 from the commercial standpoint, has yet to 

 prove its value over the systems at present in 

 vogue. Naval and military strategy have under- 

 gone changes since the necessity for wire and 

 cable communication has been removed. In the 

 Russo-Japanese War wireless telegraphy u 

 tensively employed with great precision by the 

 fleets of both powers. 



The principal system in America is that of the 

 De Forest Wireless Telegraph Company. The 

 inventor, Dr. de Forest, is a graduate of Yale, 

 and claims that he can syntonise his circuits. 

 The receiver in this system is a telephonic appa- 

 ratus, and from twenty to thirty words a minute 

 can be transmitted and recorded. The main 

 advantage claimed for it is that its usefulness is 

 not impaired by the presence of other sysh-ins 

 unless the transmitting stations are practically 

 in juxtaposition. 'The De Forest Wireless Trie- 

 graph Company transmitted a regular daily 

 news service from the St. Louis Exhibition in 

 1904 to various newspapers, and messages were 

 sent from the long-distance tower to Chicago, 

 300 miles away. The speed attained was 

 twenty-five to thirty-five words a minute. The 

 capacity of the De Forest system for operating 

 simultaneously several different transmitters was 

 clearly shown, and the ability of the operator to 

 tune his receivers at will to various transmitters 

 with different wave-lengths. The company has 

 five long-distance naval stations, and powerful 

 land stations at New York, Boston, New Or- 

 leans, St. Louis, Chicago, etc. ; and it is claimed 

 that these stations are able to operate from 300 

 to 1,200 miles overland. 



Telescope, an optical instrument es>en- 

 tially consisting of a set of lenses fixed in a tube 

 I or a number of sliding tubes, by which distant- 

 objects are brought within the range of distinct 

 or more distinct vision. The law of action by 

 which the telescope assists human vision is two- 

 fold, and that under all the varieties of its con- 

 struction. A distant object viewed by the un- 

 aided eye is placed in the circumference of a 

 large circle, having the eye for its center, and 

 consequently the angle under which it is seen is 

 measured by the minute portion of the circum- 

 ference which it occupies. Now, when the dis- 

 tance is great, it is found that this angle is too 

 small to convey to the retina any sensible impres- 

 sion all the light proceeding from the object 

 is too weak to affect the optic nerve, tins 

 limit to distinct vision results from the small 

 aperture or pupil of the eye. The telescope 

 substitutes its large object lens or reflector for 

 the human eye, and consequently receives a 

 quantity of light proportioned to its area or 

 surface; hence a distant point, inappreciable 

 by the eye alone, is rendered visible by the aid 

 of the telescope. 



The telescope almost universally employed 

 in modern times is the astronomical telescope, 

 made up of two converging lenses, known as the 

 refracting telescope. 



The best specimens of the astronomical tele- 

 scope in existence are the thirty-six-inch glass 

 of the Lick observatory and the forty-inch 

 glass of the Yerkes observatory, both made by 

 the late Alvan G. Clark. On good nights these 



