DIA-MAGSETIS3I.] UNDULATORY FORCES. ELECTRO-MAGNETISM. 



271 



of lead it will, in ordinary circumstances, be trans- 

 mitted ; and if the glass be placed between the poles of an 

 electro-magnet in an unexcited state, of course no 

 change in any direction -will be effected. The analysing 

 plate is, however, to be so turned that the transmitted 

 ray is nearly extinguished; and if the electro-magnet 

 be then brought into action by the circulation of a 

 voltaic current, the ray will instantly appear in full 

 force. Or, supposing that, in the first instance, the ray 

 had been in full force during transmission, and the 

 electro-magnet be then excited, then the ray of polarised 

 light would nearly suffer extinction. This fact at once 

 shows that magnetism has a direct action on light, 

 which, of all other agents, seems to have the least claim 

 to be considered material. 



Dr. Faraday, however, extended his experiments, and 

 was led to try how far a powerful magnetic force affected 

 matter generally ; and, in pursuit of this object, he dis- 

 covered magnetic affection in numerous gases, liquids, 

 and solids. These had a tendency of placing them- 

 selves in certain positions in reference to the poles of a 

 powerful magnet, and the direction was definite for each 

 substance tried. Gases and liquids were enclosed in 

 glass tubes ; whilst solids were chosen of such forms as 

 were found to be most suitable for the purpose. By 

 these investigations, we are enabled to classify all 

 bodies, in reference to magnetism iron, nickel, manga- 

 nese, cobalt, cerium, chromium, platina, palladium, tita- 

 and osmium having directly magnetic properties ; 

 lii: must others seemed to indicate an opposition to 

 the niagnetic force ; or rather, under certain circum- 

 stau<k=, range themselves in a direction at right angles 



to the lines of polar force in a powerful magnet the 

 metal bismuth being the most prominent in this respect. 

 Such bodies have, from this fact, been termed dia-mag- 

 net'tcs. 



If some substances in the form of powder are placed 

 between the poles of an electro-magnet, it will be found 

 that the powder will rise up into a conical form, evidencing 

 a peculiar effect of the magnetic force in relation to the 

 forces of gravitation and cohesion. Another singular 

 experiment, having the same result in a different form, 

 may also bo tried. A circular copper disc is mounted on 

 an axle, and fitted with a winch handle : of course, it 

 will readily revolve thereon in the usual manner. If, 

 however, the rim of the disc be placed vertically between 

 the poles of a powerful electro-magnet, the moment a 

 current of electricity is passed, and the iron becomes 

 magnetised, great resistance is offered to the revolution 

 of the wheel. Now, generally speaking, we exclude tho 

 possibility of any magnetic effects being inducible on 

 copper; but this experiment at once shows that tho 

 magnetic force can act on that metal in the method 

 indicated ; and herein we have another illustration of the 

 universality of its action. 



The subject of Dia-Magnetism is at present in its 

 infancy. The results already obtained go towards 

 proving that magnetism has a direct connection with the 

 forces of gravity, cohesion, electricity, and light ; and 

 that every kind of matter is susceptible of its influence. 

 These facts alone make the subject of deep interest, and 

 extend materially our views of the possibility of the 

 various kinds of forces being but modifications of ouo 

 prime agent. 



ADDENDA ON TELEGRAPHY. 



AHONQST a host of other objects which the Exhibition 

 of 1862 brought prominently out to public notice, the 

 numerous inventions connected with Electro-Telegraphy 

 rank high in importance. We have made the following 

 selections, as being of the most practical and highly 

 improved kind. In our previous pages, we have fre- 

 quently alluded to the difficulties of submarine tele- 

 graphy, the imperfect insulation of the wire, weight of 

 the cable, <fcc. The failure of the Atlantic Telegraph 

 h:is caused a vast number of inventions to be brought 

 out ; but, in most respects, that of Mr. Allan, whose 

 electro. magnetic engine we have already described, is the 

 most feasible. Its value was acknowledged by the jurors 

 in their award of the prize medal ; and, as the jury was 

 composed of the most eminent men in connection with 

 telegraphic affairs, we have no hesitation in endorsing 

 their decision, by giving an extended description of Mr. 

 Allan's cable, instruments, &c. We liave to acknow- 

 ledge his kind assistance in the matter. 



First, then, as to Mr. Allan's signal code. He re- 

 jects that of Morse, and adheres to the dot symbol alone 

 for signalling and receiving. At the signalling extremity, 

 a ribbon of paper has the dots separately punched by a 

 machine ; and in this prepared message, when passed into 

 the apparatus for transmission, and the automatic action 

 once commenced, each single punch-hole, as it passes 

 over the tooth of a small rotating spur-wheel, permits of 

 electrical contact being made within the sending-machine, 

 and of thereby inducing a perfectly synchronous move- 

 ment at the receiving extremity of the line wire, and 

 of causing a puncture in the ribbon passing through the 

 automatic apparatus there ; so that, at the same instant of 

 time, what is hole at one extremity is puncture or " em- 

 boss" at the other. Reverting, then, to the code of signals, 

 and to the method by which the message is punched or 

 marked on the paper ribbon. The apparatus employed 

 is called a "Composing Machine." It consists of an 

 oblong mahogany case, 11 inches by 8 inches, by 7 inches 

 deep, wherein are mounted a set of keys, 30 in number, re- 

 sembling those of a jnaiwfurte. The letters of the Roman 

 alphabet are printed on the touch-part of 26 of these, 

 leaving four for purposes incidental to the working of the 



machine. Within the box, and movable by the key- 

 levers, are eight punches. A ribbon of paper is made 

 to pass through tho composing machine. Now, any 

 person who can read a message, has simply to spell 

 out its words upon the keys by depressing each letter 

 of the words, and its symbol in tho code is punched 

 out at a single stroke. This operatiun, which is per- 

 fectly simple, resembles tho act of playing on the 

 piano. The message, on being punched, is passed into 

 the telegraphic instrument, wliich, from its automatic 

 character, continues to work on, till the whole i 

 through ; and the corresponding automatouism of tho 

 receiving apparatus is brought into play at the same 

 instant. Further, any one may have his own " com- 

 posing" or punching "machine," and adopt his own code 

 of signals, by the very simple device of transposing tho 

 Roman characters on the touch-part of the keys. 

 Secrecy is secured by this means ; and the message on 

 being punched, it may be, in a government or business 

 establishment, if dispatched to the telegraph office, can 

 be at once sent through to the confidential receiver of 

 the same, who is in possession of the cipher to read the 

 message, whilst tho telegraph office-clerks know nothing 

 whatever of its import. Further, this "composing 

 machine," taken with the system of telegraphy of wliich 

 it forms a part, possesses considerable interest to the 

 newspaper press, as a probable means of cheapening what 

 is a heavy cost in their annual expenses namely, the 

 telegraph despatches. One single punched ribbon may 

 be carried continuously and simultaneously over any 

 number of sending machines, and the same political 

 news or parliamentary speech may be- sent to half-a- 

 dozen distant places from tho same centre say from 

 London at the same time ; and all this can be done by 

 so many boys as there are receiving places. Again, to 

 receive messages depending upon either visual or audible 

 signals, tho clerk must always be in attendance ; and 

 when the distance is great, over land or water, so as to 

 embrace many degrees of longitude, that attendance 

 must be unremitting night and day. The clerk, in such 

 a case, is a part of the instrument, and the complement 

 of it ; he can no more withdraw himself an instant than 



