TELEGRAPHS.] 



UNDULATORY FORCES. ELECTRO-MAGNETISM. 



273 



, MORSE. 

 ALLAN. 



only increases the conducting power of the cable in the 

 proportion which the conductivity of steel bears to that of 

 copper, which is about one-seventh. To obtain the same 

 capacity for the transmission of messages in a cable of this 

 kind, as in a cable in which copper forms the sole conductor, 

 the dimensions of the conductor must be increased to give 

 the same ratio of conduction to induction. The insulating 

 material, of course, requires protection in these as in other 

 cables." The latter portion of this report we consider 

 scarcely correct. We have now before us a specimen, in 

 which the compound conductor has no greater surface 

 than the ordinary copper strand of the same conducting 

 power. We intended giving an illustration of this prin- 

 ciple of cable, but it is so few in parts, that we can readily 

 convey it to our readers, by simply saying that it is 

 composed of a No. 8 soft copper wire, surrounded with 

 25 No. 25 best steel wires ; this is insulated with four 

 separate coatings of best gutta-percha, and then finished 

 in a skin of hemp, merely to protect it during sxibmergence ; 

 the conducting power of the core is equal to 520 Ibs. of 

 copper, and it is insulated with 550 Ibs. of gutta-percha 

 per nautical mile ; in diameter, it measures five-eighths of 

 an inch; weight per naut. in ship is 13 cwt. , with a 

 specific gravity of 17 ; and it is calculated to bear 7,500 

 fathoms of itself in water, without elongating one per 

 cent. " Mr. Allan considers this cable suitable for a 

 distance of 2,000 nautical miles, and a depth of 3,000 

 fathoms, the shore ends of course to be heavily protected. 

 A cuble of this description has tho great advantage of 

 very simple to manufacture ; in fact, it could be 

 i'iit 'y finished by the manufacturer of telegraph cores. 

 The are many instances of the gutta-percha core 

 receiving injury during the process of iron wire covering, 

 which have only been detected after tho cable has been 

 submerged." 



The following cut illustrates Mr. Allan's method of 

 recording messages, for use either on land or submarine 

 telegraphs. As previously mentioned, the dot system, 

 which he prefers, saves considerable time in transmitting 

 the message. 



20 



3o 



In the cut, Morse's system is compared with that of 

 Mr. Allan's ; and it will be seen that the latter has tho 

 advantage, in respect to space occupied on the receiving- 

 tape, and that the code of signals is entirely different. 

 The length of the dash is done away with, and the space 

 between them economised. In Allan's arrangement, 126 

 currents produce the alphabet ; against 164 required in 

 the instrument employed in the system of Morse. The 

 proportion of time is as 196 to 200 for the whole 

 alphabet ; and as 33 to 49 for a word ; or generally about 

 fifty per cent, is saved. 



TVER'S TKAIN TELEGRAPH. The numerous accidents 

 which have taken place, owing to trains overtaking each 

 other on the same line of rail, have given rise to numer- 

 ous inventions, intended to prevent the recurrence of such 

 casualties. Amongst them, we may notico Tyer's patent 

 train telegraph. In this arrangement, a dial-face is 

 placed at each station, on which needles are worked by 

 electro-magnetism. A bell aiid gong are also provided, 

 for calling the attendant's attention. The dial-face is 

 divided into two parts one for the up, and another for 

 the down line ; and on the right and the left of the face, 

 the words "Train on Line," and " Line Clear," arc en- 

 graved. According to the system adopted in this plan, 

 each signal station communicates with the signal station 

 on each side of it, so an to announce both the approach 

 and departure of each train. The receiver of a signal 

 cannot alter it ; and a signal once given remains fixed, 

 until the next signal u sent. The lino of railway is 



VOL. L 



divided into sections by the signal stations ; and no train 

 is permitted to pass one of the stations until the signal 

 has been received that the next station in advance is 

 quite clear. The mechanical arrangements are extremely 

 simple, and the system itself is equally so. Its universal 

 adoption would doubtless go far to prevent the possi- 

 bility of collision by trains overtaking each other during 

 a long journey. On short station-lines, such a plan 

 would seem to be indispensable. 



WHEATSTONE'S PRIVATE TELEGRAPH. Much of the 

 credit of all our telegraphic arrangements in this country 

 is due to Professor Wheatstone, who, for many years, 

 has been indefatigable in his exertions to bring the sys- 

 tem into a state of perfection. The first attempts were 

 confined to connecting our large cities together by means 

 of telegraphic wires. Another step was that of extending 

 the telegraph, by means of submarine cables, to foreign 

 countries. Eventually, large warehouses were furnished 

 with telegraphic apparatus, by which much time was 

 saved by the telegraph doing the work of messengers. 

 District telegraphs were another development of the 

 system ; and, at last, the Universal Private Telegraph 

 Company has stepped in to give private individuals the 

 opportunity of using the electric current for the expres- 

 sion of their wishes in any direction, and under their sole 

 control. We can well remember hearing it said, some- 

 what derisively, some years ago, by a learned but crotch- 

 ety professor, "that some day, electric wires would be 

 as common in London as gas and water-pipes." This 

 prophecy has been exceeded in its fulfilment ; for the 

 number of electric wires in many streets of the metro- 

 polis, far exceeds that of the pipes of both classes we have 

 named. 



It is, of course, requisite that the instruments em- 

 ployed in private houses should bo BO simple, both in 

 their working and indications, as not to be liable to get 

 No. 1. The Communicator. 





out of order, or to require much practical knowledge ID 



