TELEGRAPH. 



flood at a particular fentence, the other index would, at the 

 fame time, point out the fame fentence. Now this operation 

 could be equally well performed when the two veffels were 

 moved to any dillance afunder, provided the obfervers were 

 within fight of each other, to be able to make the requifite 

 fignals for opening and (hutting the cocks of both veffels at 

 the fame moment. The author thus defcribes the ufe of this 

 inftrument : The two veffels being prepared and adjulled, they 

 muff be carried to the two places where the fignals are to 

 made and obferved ; water is poured into each, and the floats 

 and indices are put into the veffels. When any of the events 

 which are written upon the indices (hall happen, a torch or 

 light is raifed, which muft be held aloft till fuch time as ano- 

 ther is raifed by the party to whom it is direfted. (This 

 firft Cgnal is only to give notice that both parties are ready 

 and attentive.) Then the torch or other light muil be 

 taken away, and the cocks fet open inllantly by both parties. 

 When the interval ordivifion on that part of the index where 

 the event, of wliich notice is to be given or written, (hall be 

 fallen to a level vpith the veffels, then the man who gives the 

 fignals lifts up his torch, and on the other fide, the corre- 

 fpondent fignal maker immediately fhuts the cock of his veffel, 

 and looks at what is written on that part of the (lick which 

 touches the mouth of the veffel ; on which occafion, if every 

 tiling has been executed exaftly and equally on both fides, 

 both parties will read the fame thing. 



The proper telegraphic art was not wholly unknown to 

 the ancients. The Greeks and the Romans made ufe of pots 

 filled with lighted twigs and ftraw for fignals, over which 

 they poured oil ; and thefe being placed in certain rows, ex- 

 preffed certain letters, according to the order in which each 

 row was lighted. 



Polybius defcribes a new method of communication, which 

 was invented by Cleoxenus, or by Democlitus, and vi'hich 

 Polybius himfelf very much improved. It poffeffes the prin- 

 cipal advantage of the modern telegraph, -via. that, by means 

 of fignals, it communicates the letters of the alphabet, and 

 can therefore be ufed to exprefs any thing which can be 

 required. It is only inferior to the telegraph in the 

 means of making the fignals, which is by the light of 

 torches, and rather complicated, fo that it would be te- 

 dious to tranfmit any thing more than fhort fentences. 

 Polybius defcribes this method, which he calls Pyrfia, in the 

 following manner : Take the letters of the Greek alphabet, 

 and divide them into five parts, each oi which will confift of 

 five letters, except the laft divilion, in which there will be only 

 four. Let thefe be fixed on aboard, in five columns. The man 

 who is to give the fignals is then to begin by holding up two 

 torches, which he is to keep aloft till the other party has alfo 

 fiiewn two : this is only to denote that both fides are ready : 

 thefe torches are then withdrawn. Both parties are pro- 

 vided with boards, on which the letters are difpofed as for- 

 merly defcribed. Then the perfon who gives the fignal is 

 to hold up torches on the left hand, to point out to the 

 Other party, from what column he (hall take the letters as they 

 are pointed out to him : thus, if the letter is to be from the 

 firft column, he holds up one torch ; if from the fecond, two ; 

 and fo on for the others. He is then to hold torches on the 

 right hand, to denote the particular letter of the column that 

 is to be taken. All this muft have been agreed on before- 

 hand. The man who gives the fignals muft have an inftru- 

 ment (JiQTT^o., perfpehive), confifting of two tubes, and fo 

 placed, that by looking thnVUgh one of them he can fee only 

 the right fide, and looking through the other, he can only fee 

 the left-hand fide of him who is to anfwer. The board muft 

 be fet up near this inftrument ; and the ftations on tlie right 

 and left muft each be furrounded with a wall ten feet broad, 



and about the height of a man, that the torches raifed abote 

 it may give a clear and ftrbng light, and that when taken 

 down they may be completely concealed. 



The ftegaiiographia trithemiana of a Benedidline monk, in 

 the fifteenth century, feems to have been fomething of the 

 fame kind ; but the firft recorded experiment, after the man- 

 ner of the Greeks, is defcribed by Kircher, in his " An 

 magna Lucis et Umbrae," under the title of Cryptogamia 

 catoplrlca ; it was however imperfeft, and could be em- 

 ployed only at a certain diftance. Schott, in his " Technics 

 curiofa," propofes, after an anonymous author, to ereft pofts 

 upon an eminence, fo as to be diftinguiflied through a tele- 

 fcope, and on which proper fignals could be elevated, as might 

 be neceffary. 



The marquis of Worcefter, who is fojuftly celebrated for 

 having firft dilcovered that the force of fteam could be 

 applied to mechanical purpofes, brought telegraphic com- 

 munication to a confiderable degree of perfeftion, if at 

 leaft we give him credit for having really effefted every 

 thing which he mentions in his Century of Inventions. 

 This little tra& was pubhlhed in 1663, and contains the 

 following articles. 



" No. 6. How at a window, as far as eye can difcover 

 black from white, a man may hold dii'courfe with his corre- 

 fpondent, without noife made, or notice taken, being accord- 

 ing to occafion given and means afforded, ex re natd, and no 

 need of provifion before-hand, though much better if forefeen, 

 and means prepared for it, and a premeditated courfe taken 

 by mutual confent of parties. 



" No. 7. A way to do it by night, as wejl as by day, 

 though as dark as pitch is black." 



The marquis gives us no idea of the means which he ufed 

 for exhibiting his fignals, by which we can judge of the prac- 

 ticability of his plan for communicating any detailed intel- 

 hgence. 



Kefsler, in his Concealed Arts, advifes charafters to be cut 

 out in the bottom of a caflc, fo as to appear luminous when 

 a light is placed withinfide, and the charafters muft be 

 changed fucceffively to exprefs words and fentences. 



Dr. Hookers Telegraph. — The firft idea of a telegraph upon 

 a fimilar conftruftion to thofe ufed at prefent, was fuggefted 

 by Dr. Hooke towards the end of the laft century, the 

 fiege of Vienna by the Turks having turned his attention to 

 the bufinefs. He gave the firft complete defcription of fuch 

 a machine, as appears by the following extraft, from a paper 

 of his, read before the Royal Society on the zift of May, 

 1684. " I propofed (fays he) fome years fince, a method 

 of difcourfing at a diftance, not by found but by fight : I 

 fay that it is poffible to convey intelligence from any one 

 high and eminent place, to any other that is in fight of it, 

 though thirty or forty miles dirtant, in as ftiort a time almoft 

 as a man can write what he would have fent ; and as fuddenly 

 to receive an anfwer, as he that receives it has a mind to re- 

 turn it, or can write it down on paper. Nay, by the help of 

 three, four, or more eminent places vifible to each other, lying 

 in a ftraight line, 'tis poffible to convey intelligence almoft in a 

 moment, to tvs'ice, or thrice, or more times that diftance, with 

 as great a certainty as by writing. 



" For the performance of this, we muft be beholden to 

 a late invention, which we do not find any of the ancients 

 knew ; that is, the eye muft be aflifted with telefcopes, that 

 whatever charadljrs are expof^d at one ftation, may be made 

 plain and diftinguifhable at the other. 



" Firft : For dij ftations, if they be far diftant, it will be 

 neceffary that they fliould be high, and lie expofed to the 

 flcy ; that there be no higher hill or part of the earth be- 

 yond them, that may hinder the diftinftnefs of the charac- 

 ters, 



