UNDULATORY FORCES ELECTRO-MAGNETISM. [MOIUSK'B TELTOKAPH. 



cable. The object he had in view, was to ascertain the 

 speed with which a current of definite intensity and 

 quantity pawed through various lengths of conducting 

 wire; and also to discover the retardation which the 

 current suffered from the resistance arising from wires 

 of different thicknesses. He employed an arrangement 

 very similar to that wo have already described in a pre- 

 vious page, and which is used in BakewelTs instrument 

 By these means, ho found that the same current pro- 

 duced a dot through say 200 miles ; a dash through 500 

 miles ; and a longer lino through a circuit of 900 miles ; 

 and so on. It was to these experiments we referred 

 when speaking of the influence which a gutta-percha 

 coated wire has on the speed of signals trnnsiiiiitr.l 

 through long cables.* We have first introduced Mr. 

 Bakewcll's copying telegraph, aa being comparatively 

 simple to some we shall have to mention ; and shall now 

 proceed to describe the inventions of Mr. Bain, and also 

 of Mr. Morse, with others, which have been very exten- 

 sively used for various purposes. 



BAIN'S ELECTRO-CHEMICAL TELEGRAPH. 



AMONGST the earliest inventors in connection with elec- 

 tro-telegraphy, Mr. Bain is well known. We believe 

 that he was one of the first to produce a printing 

 telegraph, which, however, was constructed with or- 

 dinary types. These were moved by means of mechan- 

 ism actuated by electro-magnets, and each letter was 

 successively brought to its proper place by complicated 

 arrangements. After being inked, it was pressed on a 

 receiving surface, which, when finished, presented a 

 tiinilnr appearance to ordinary printed matter. A 

 model of this arrangement was first publicly pro- 

 duced and explained by its inventor, many years ago, at 

 the Polytechnic Institution, Regent-street, London ; but 

 we are not aware that it ever came into extensive 

 use. Mr. Bain was also well known for his ingenious 

 arrangement of electro-magnetic clocks, one of which was 

 for some time in operation at the above-named institu- 

 tion. His electro-chemical telegraph is constructed on 

 somewhat similar principles to those we have illustrated 

 already, t As in IJakewell's apparatus, Mr. Bain ob- 

 tains marks on prepared cloth, intercepting the surface 

 of the transmitting arrangement by means of non-con- 

 ductors ; producing, however, dots and dashes, instead 

 of continuous lines. Combinations of the marks pro- 

 duce letters, as the following instance will illustrate. 



A- D 



B E- 



C--- F <frc.,fcc. 



It will be unnecessary for us to enter into detail with 

 respect to the mechanical arrangement of the apparatus ; 

 for the principle is so fully illustrated by the elementary 

 instrument already referred to : but we may add, that 

 the continuity of the current is intercepted, and the 

 letters represented, by means of perforated paper, each 

 of which corresponds, in its perforation, to, and produces 

 marks, such as those represented above. The message, 

 in fact, is perforated in paper or cardboard by means of 

 punches ; and is then placed ill the transmitting arrange- 

 ment ; after which it is sent, in the manner we have 

 already described, to the receiving instrument at the 

 distant station, and is then printed on the prepared 

 cloth. 



Various inventions have been brought into public 

 notice being improvements, modifications, or original 

 productions in the form of electro-chemical printing 

 telegraphs; but we shall not enter into any investiga- 

 tion of them, as their use has not been adopted, to any 

 extent, for telegraphic purposes. 



MORSE'S TELEGRAPH. 



AMOXOST the great variety of telegraphic instruments 

 which have been employed in foreign countries, that 

 invented by Mr. Morse, of America, has been, perhaps, 

 the most extensively adopted. In it, electro-magnets 



St* ant,, p. 305. 



t Antr, p. 200 ; Fig. 30. 



are employed in a similar manner to that of Mr. Bain's 

 invention : in fact, the similarity of the two instruments 

 is so great, as to have given rise to litigation in the 

 American courts, which have had to decide on the re- 

 spective rights of the inventors. Mr. Morse, however, 

 seems to have been original in his ideas; and he has 

 worked them out to a most successful issue ; for nearly 

 the whole of the American, and some continental, lines 

 are worked under his patent. 



In speaking of the needle instrument, we mentioned 

 that its indications were effected by its deflections. Mr. 

 Morse's arrangement is constructed on entire', y different 

 principles ; and, except in some parts of the mechanism, 

 the details are just such as we have described in 

 Bain's instrument. The signals are transmitted in a 

 similar manner, and the notation is that of dots and 

 dashes of unequal length or interval. The following is 

 a portion of the telegraphic alphabet employed by Air. 

 Morse. 



A E I 



B 

 C 



F 

 G 



.1 

 K 



D H L A-c.,A-c. 



A larger amount of electric force is required to work 

 Morse's arrangement than the needle telegraph, and 

 hence the employment of "relay" magnets, by means 

 of which the first current "transmitted from a distant 

 station, brings into operation another cunent at the 

 station at which the message is received. Tiia necessity 

 cif this will be at once seen if it be borno in mind, that. 

 whilst a weak current will readily deflect a magnetised 

 needle, it requires one of considerable force to convert a 

 piece of soft iron into a magnet. J The arrangement of a 

 relay magnet is illustrated in the following engraving. 



Fig. S3. 



With respect to the speed at wluch signals may be 

 sent by this plan, its advocates maintain that it equals 

 that of the needle system. It has other advantages ; for, 

 owing to the nature of its arrangement, and considering 

 that the electro-magnetic force is generated at the 

 moment it is required, there can be no risk of inter- 

 ference by atmospheric influence, which is almost always 

 operating on the apparatus of the needle instrument. 



Numerous modifications of the Morse principle have 

 been made in America, and on the continent; but as wo 

 cannot enter into details, which, whilst interesting, 

 invite no special novelty in principle, we shall not 

 further refer to them than to state, that our readers may 

 obtain full information in Mr. Shaffuor's TtUgrapA 

 .Manual, from which our two last illustrations have, by 

 his kind permission, been copied. 



THE MAGNETO-ELECTRIC TELEGRAPH. 



AMONGST other instruments involving no great novelty 

 in the indicating part of the arrangement, is the magneto- 

 electric telegraph. Some years ago, a company was 

 formed for the purpose of carrying out a system of 

 telegraphy, in which a current of electricity, produced 

 by magnetic induction, was to be employed in place of 

 the old plan of voltaic batteries. It wax urged that the 

 new plan offered all the advantages of the old one, and 



t Sec ante, p. 211. 



