tlefcriptlon of a Portable Telegraph, , J2.^ 



SUPPLEMENT. 



S, 



'INCE the Royal Irifh Academy did me the honour to accept of my eflay on the Tele- 

 graph, I have made material improvements in its conftrui^ion, which I think it my duty to 

 communicate. 



In September i79<5, the Lord Lieutenant ordered me to prepare Telegraphs for an expe- 

 riment before his Excellency. In confequence I con(lru£ted four new Telegraphs. — I had 

 found that the large machines thirty feet high, with which my fons talked, in September 

 1794, acrofs the channel between Ireland and Scotland, were liable to accidents in ftormy 

 weather : my firft confideration therefore was to contrive fome means of furling their 

 canvas when they were not in in ufe ; and, from the rigging of fliips, it was obvious that 

 cordage was for this purpofe preferable to inflexible braces of wood. I therefore adopted 

 die following conflruftion : 



A. (fig. 4. Plate XIV.) a hollow axle-tree made in feparate pieces hooped together in 

 the form of a double truncated cone, on the middle of which is faftened a wheel of wood 

 (b, fig. 4) with eight notches cut out (a, fig. 4) to receive eight ribs (r. r. r. r, r. r. r. r 

 fig. I and 2.) Thefe ribs turning on a ftrong iron ring, fhut up like the ribs of an um- 

 brella, and are raifed and adjufted by cords paffing through eight holes in the flanches or 

 fhoulders (F fig. I. 4.) Thefe flanches and tliofe at (f. fig. 2 and 4) ferve to keep the 

 machine in its place upon the ftands which fupport it (fig. 2) ; the cords are drained and 

 faftened like the cords of a tent (c. c. &c. fig. 2.) 



Where permanent buildings are not required, fupports for thefe machines may be con- 

 ftrudled in the following manner. Two ftands, each of them made of two pieces of wood 

 fimply bolted together, as (fig. 3 ), muft be ere£l:ed, and held fteady by means of cords (c. c.) 

 faftened to common tent pegs, as in (fig. 2 P. P. P.) When the machines are large, fmall 

 piles fliould be ufed inflead of pegs, and running tackle (t.) fliould be ufed both for the 

 cords of the pointers, and the ftands. A number of minute circumftances Ihould be 

 attended to in the conftru£tion and ufe of thefe machines •, but I do not think it proper to 

 detail them to this Academy ; they fhould appear in a different place *. 



Befides rendering the Telegraph fafe againft ftorms, and more eafily manageable, I found 

 by experience that one machine could be made to perform the fame eflieft as four, with but 

 little lofs of time ; what took up four minutes with four pointers, can be conveyed in five 

 mJnutes by one. I have alfo found that, by anfwering each fignal or number ftiown at 

 every ftation, all poftibility of miftake is avoided. 



I believe that, in other eftabliftimerits of this fort, it has been found that thick and foggy 

 weather has occafioned more interruptions than were expedted. With my Telegraphs, I 



• Formerly, in France, every engineer who condufted.any public work, was obliged to lodge in a public office 

 exaft drawings, with minute defcriptions, of every part of and procefs of his operations. Numberlefs fmall im- 

 provements in workmanfliip and tools were prcferved by thefe means, and by degrees were coUedled inta 

 publications of general circulation. 



I was required to deliver drawings of all the machinery I employed in the work carried on at Lyons'in 1772, 

 for turning the courfe of the Rhone : 



But, in the tranfiftiont of a literary Society, fuch details would be tedious and improper. 



U u 2 hare 



