FROMENT'S TELEGRAPH.] UNDULATORY FORCES. ELECTRO-MAGNETISM. 



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saved the cost of chemicals, the wear and tear of plates, 

 battery cells, <tc. ; that the current produced by magne- 

 tism had greater intensity; and, lastly, that the first 

 was the only cost of the source whence electricity was 

 to be obtained. Our readers have already been ac- 

 quainted with the magneto-electric machine ;* and we 

 shall, therefore, not enter into any further detail, as the 

 indicating instrument is simply a modification of the 

 ordinary needle instrument. We were informed, two 

 years ago, by the superintendent of one of the chief 

 stations on the Glasgow and South- Western line, that 

 the magneto-electric machine had been given up, and 

 that the old plan of the voltaic battery had superseded 

 it. If so, the distinctive character of the company no 

 longer exists. 



ALPHABETICAL TELEGRAPHS. 



ONE of the earliest forms of electric telegraph, was that 

 of a circular plate, around the edge of which were en- 

 graved the letters of the alphabet. An index moved in 

 the centre ; and, in fact, the arrangement was exactly 

 similar to that of a watch, with the exception that 

 letters were employed in place of figures. The index- 

 hand was moved by electro-magnets ; and, of course, 

 the receiving and signalling instruments were constructed, 

 in all respects, precisely alike in the manner already 

 described in connection with electric clocks, f The 

 x had to be moved from letter to letter passing 

 over those which were not required in the word, and 

 resting opposite to that which was included in it. It 

 thn* happened, in many words, that the index had to 

 travel frequently over the dial-plate before a word 

 could be spelt. Thus, supposing there were two " e's" in 

 a word, the index would have to pass twenty-five letters 

 before the " e'' would be again reached ; and BO on. The 

 plan, however, is remarkably simple, for any one can 

 read the indications; and it requires no previous in- 

 struction for its successful employment. At the present 

 time some of its modifications are in use ; and an in- 

 vention, by Professor Wheatstone, has lately been adopted 

 by the Universal Private Telegraph Company the 

 object being to maintain electrical communication be- 

 tween, and in, private dwelling-houses. 



Froment's alphabetical telegraph will assist our readers 

 in understanding the principle of the arrangement of 

 these alphabetical instruments. In front is a key-board, 

 constructed similar to that of an ordinary pianoforte; 

 and connected with this is a dial, on which are engraved 

 Fig. 34. 



the letters of the alphabet and the numerals. A similar 

 instrument, of course, is placed at each station or house ; 

 and wires connect the two in the usual manner. All 

 that is required to transmit a message, is to press down 

 the key of the letters composing the words of the message, 

 wliich are simultaneously shown on the signalling and 

 Sec ante, p. 258 ; Fig. 22. 4 See ante, p. 253. 



receiving instrument. The apparatus, except with 

 respect to its internal mechanism, is remarkably simple ; 

 and even a child may soon be taught its use. Fig. 34 

 illustrates the appearance of one of these instruments. 



The alphabetical system of telegraphs has becu partially 

 applied to the purpose of railway signals ; but instead of 

 the entire alphabet being printed on the disc, separated 

 signals, such as "train started," <tc., are employed. An 

 instrument is placed at each station on the fine ; and 

 thus a system of constant signalling may be readily 

 maintained. There is, however, considerable difficulty 

 in keeping the signals identical at the same moment in 

 each instrument ; and in experiments we have tried with 

 two such instniments, exactly opposite indications were 

 received to those sent ; a result which would be most 

 serious in practice. On many of the railway lines, 

 especially at the extremities of tunnels, the old needle 

 system has been introduced ; and as the number of signals 

 is small, it is found the most convenient and certain plan. 



The limits of this work prevent us extending to fur- 

 ther telegraphic details ; and we shall, therefore, uow draw 

 attention to some minor applications of the instruments 

 we have described, and of the principles already ex- 

 plained ; amongst which are the following. 



WIND AND WEATHER REPORTS. A complete system 

 of telegraphy is now established, between the Admiralty 

 Office and the Royal Exchange, London, with all the 

 outposts and chief towns in this country and foreign 

 parts ; and it is impossible to over-value the results wliich 

 have accrued. Since the discovery of the general law of 

 storms, it lias been most desirable to make simultaneous 

 communication from a common centre, so that informa- 

 tion may subsequently be diffused as to the kind of 

 weather which may probably be expected. We have not 

 yet arrived at sucli precision of information as will permit 

 us to foretel, to an exactitude, the atmospheric changes 

 which are continually occurring in a climate like ours ; 

 but we can, to some extent, approximate to truth ; and, 

 in many instances, the conclusions which have been drawn 

 from the facts collected by the telegraph, have resulted 

 in paving many lives, through timely notice which has 

 been sent to different parts of our coasts. 



Our readers will understand this better if we give a 

 few facts in reference to the cause and indications of & 

 coming storm. The most dangerous kind of tempest is 

 that called the "cyclone;" which is an immense eddy of 

 wind, having a calm centre and circumference. Vessels 

 in any intermediate place are exposed to the full vio- 

 lence of the storm ; but, from their position, the cap- 

 tain is unable to judge of its extent. Now, if we learn 

 the direction of the wind over an extensive area of 

 country, and also the rise or fall of the barometer (wlu'ch 

 is, at all times, a sure indication of coming atmospheric 

 changes), we obtain data on which tolerably accurate 

 conclusions may be drawn. Amongst those who have 

 taken a lively interest in this matter is Admiral Fitzroy, 

 whose remarks on the subject we shall quote. "I do 

 not hesitate to affirm (and it is more than forty years 

 since I bought Daniell's first work on Meteorology), that 

 the peculiarities of our winds and climate are now suf- 

 ficiently known to make it practicable to foresee every 

 extensive storm ; and, when no such change is impend- 

 ing, to give the negative information often valuable- 

 thai no tempest need be feared." 



On this matter we may remark, that much useful in- 

 formation might be afforded by private individuals 

 undertaking the duty of keeping a register of the 

 barometric indications, the direction of the wind, and 

 other meteorological phenomena. These might be for- 

 warded, periodically, to the secretary of the Meteoro- 

 logical Society, or to the Admiralty Office, London : 

 and if a tolerable amount of accuracy were maintained 

 by observers, the extent of our general information 

 would be largely increased. 



The necessary facts having been gained by means of the 

 telegraph, the next step is to use that instrument for the 

 purpose of diffusing the instructions from head-quarters ; 

 and this is followed by the employment of signals, which 

 are hoisted at some prominent place on the coast, near 



