TELEGRAPH. 



TELEGRAPH. 



ad by which throe number*, or rather throe numerals combined to 

 form one number, might be readily eipimsml, To remedy this defect, 

 he, in 1807 (before he hid eeen the French semaphore), derived what 

 he termtid a i*>lyKnmmatio telegraph," a description of which ww 

 pnblUhod in Tillochs < Philoeophloel Magaiine.' vol. xxix. This 

 machine, ty. 6, consisted of four poet*, at the top of each of which wu 



Hi. S. 





pivoted a pair of arms. Each pair of arms was capable, by assuming 

 the various position* indicated by the dotted lines added to the first 

 pair, of forming more than a sufficient variety of distinct signals to 

 express any of the numerals or the ; and consequently the whole 

 machine could represent any number composed of not more than four 

 figures, besides having several signal* to spare. In 1809 Captain 

 Puley saw the French semaphore, which he described in the following 

 year, together with a modification of his own polygrammatic telegraph, 

 founded upon it, hi the thirty-fifth volume of the periodical just 

 mentioned. This simplified polygrammatic telegraph, represented in 

 tj. 6, has three pain of arms, representing hundreds, tens, and units, 

 pivoted to different parts of the same vertical 

 post. This contrivance is adopted by Lieu- 



i IK tenant-Colonel Macdonald, with very trifling 



N. variation, in his ' Treatise explanatory of a new 



System of Naval, Military, and Political Tele- 

 graphic Communication,' published in 1817. By 

 v \ the addition of a ball and a vane at the top of 



, _, ' mast, IT i. DBMS machiM b4 tin' same 



power as Maodonald's thirteen-shutter telegraph ; 

 as each pair of arms is capable of assuming 

 fifteen distinct positions. Another semaphore 

 on the same principle was submitted to the 

 Society of Arts in 1821, by Lieutenant N. H. 

 Nicolas, and described, together with a method 

 of applying a shifting key to telegraphic com- 

 munications, for the purpose of insuring their 

 secrecy, in the thirty-ninth volume of the 

 Society's 'Transactions.' The telegraphs upon 

 the commercial line of communication esta- 

 blished between London and the Downs were constructed upon another 

 modification of the polygrammatic principle ; four pairs of arms being 

 employed, but mounted upon two posts instead of one, as in Nicoku's 

 semaphore, or four, a* in the original design of Captain Pasley. 



In 1S16 it was determined to change the Admiralty telegraphs into 

 semaphore* constructed on the principle of those used in France, with 

 the improvement* suggested by Sir Home Popham, who had previously 

 don* much for the improvement of naval signals. The action of 

 Popham'* semaphore is explained by jig. 7, in which dotted lines are 

 added to show the various positions in 

 which the arms may be placed, and nume- 

 rals to show the numbers indicated by 

 those positions. Only two arms are em- 

 ployed ; but aa they are mounted upon 

 . separate pivots, each of them can assume 



^if.. Js six different positions, and the two together 



are capable of affording forty-eight signals ; 

 which number, though less than that given 

 by the six-shutter telegraph, is sufficient to 

 express the letten of the alphabet and the 

 Arabic numerals, and to leave thirteen 

 signal* unappropriated, for abbreviations 

 and arbitrary signs. This kind of seina- 



" Ml) A -M'...] in tlir 



-^P J 5' Society of Art* Transactions,' vol. xxxiv.) 



was used at the government stations until 

 superseded by the electric telegraph. 



The vert cal post of this telegraph was a 

 hollow hexagonal mast, which, turning on 

 a pivot at it* foot, and in a collar where it 

 passed through the roof of the observatory, 

 could be moved so as to display it* signal* 

 in any direction. The moveable arm* were 

 provided with balance-weight* in the form 

 of muses of metal attached to their shorter 



ad*, vry new to UM pivot* upon which they tamed, by which means 

 they could be moved in any direction with the exertion of a very small 

 MM; and they were made, when out of use, to fall into groove* or 

 '""mi UM post, to M to become invisible. The movement* were 

 Acted by moan* of two winch- handle* near UM base of the mast, 

 wiUun UM cabin, one lot each ana. The winch-handle* turned two 



rii, ;. 



small bevel-wheels, which communicated motion by means of two 

 horizontal bevel-wheels to long upright shafts or rods, which passed up 

 the inside of the hollow post of the telegraph. At the upper ends of 

 these rods, which were held steady by suitable bearings, were endless 

 screws, working into toothed wheels fixed upon the axes of the arms, 

 and thereby communicating motion to them. In order that the person 

 who worked the machine might know precisely when the arms were 

 brought to the required positions, nimiliu- endless screws were added 

 near the lower ends of the vertical rods, to give motion by toothed 

 wheels to indexes, which gave a miniature representation of the motion 

 of the arms. Excepting these indexes and the winch-handles, the 

 whole apparatus was inclosed hi the vertical shaft of the telegraph, on 

 the outside of which small blocks were added, to enable a man, with 

 the assistance of a rope from the top of the post, to ascend the machine 

 for the purpose of cleaning and oiling it. 



About the same time, Sir Home Pophani proposed a modification of 

 the semaphore for marine purposes, which, he conceived, would be 

 found very advantageous for the merchant-service, by superseding the 

 necessity for a costly set of signal-flags, the expense and wear and tear 

 of which formed a serious objection to a system of general telegraphic 

 communication at sea, excepting in the ships of the East India Com- 

 pany. His proposed sea-telegraph would not, it is stated, cost more 

 than fifty shillings at first, and its wear and tear would not amount to 

 five shillings a year. As the height of an apparatus resembling the 

 land-semaphore would be objectionable for marine purposes, Popham 

 proposed to use two posts, 12 feet 2 inches high and 6 inches thick, 

 each having fa single arm, 6 feet 4 indies long and 10 inches broad, 

 pivoted to the top. but not falling into a slot in the post, as in the 

 last-described machine. In a small slot at the top of each post is a 

 grooved pulley or sheave, fixed upon the same axis as the arm ; and at 

 a convenient height from the bottom of each post another precisely 

 similar pulley is mounted in like way, its axis passing through the 

 post, and carrying a small wheel with four handles at right angles with 

 each other, by which the machine is worked ; the motion of the lower 

 pulley being communicated to the upper one, and consequently to the 

 arm, by an endless rope, which has two or three turns round each of 

 the sheaves, and passes up by the sides of the post When the tele- 

 graph is in use, the posts may be attached to the sides of a vessel by 

 stepping their lower ends into blocks fixed for the purpose, and lashing 

 them to the bulwarks ; or they may be mounted upon trucks, so as to 

 be readily moved from one part of the ship to another. The descrip- 

 tion of this machine in Sir Home Popham's communication to the 

 Society of Arts mentions but four positions for each arm, and states 

 that when placed in the four positions diagonally to the post, one arm 

 denotes 1, 2, 3, and 4, and the other 5, 6, 7, and 8. This arrangement 

 gives twenty-four distinct signals, and avoids the possibility of mis- 

 taking the horizontal for an inclined position of either arm, of which 

 there might, owing to the motion of the ship, be some risk. 



Major-General Pasley. in a pamphlet published in 1823, entitled 

 ' Description of the Universal Telegraph fur Day and Night Signals,' 

 abandons the polygrammatic principle, and adopts the simple form 

 shown in fy. 8, which represents what he styles the " universal tele- 



4 



Fig. 8. 2 



graph," as adapted for day-service. It consists of an upright post with 

 two arms, both attached to one pivot at its upper extremity. Each 

 arm is capable of assuming the seven positions indicated in the cut, 

 besides what is called the ttop, which is made when turned down and 

 obscured by the post. Twenty-eight distinct signals may therefore be 

 made by the apparatus, as shown in the subjoined table ; these being 

 more than sufficient for the letters of the alphabet, though not 

 numerous enough to allow of a full alphabet and the numeral 

 characters. 



Table of the irparatc or dutinct Signals given ly I'mley'i L'nirenal Teltfraph. 

 1 6 15 25 86 56 



1 r 16 M 87 67 



8 13 17 27 45 67 



4 II 18 84 46 



5 14 24 35 47 



It had been found, in using Sir Home Popham's ship-semaphores 

 that uncertainty was occasioned by the signals being sometimes seen 

 in reverse, in which case one number or sign would be confounded with 



