3843.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



21 



day (16th May last) brought into operation for nearly 20 miles on the Great 

 Western Railway. 



It is no slight proof of the energy with which Mr. Cooke followed up his 

 great object, in contradistinction to the proceedings of others who had been 

 experimenting with the subject for many years, that within three weeks of 

 his first conceiving the idea, he had constructed at Frankfort two galvano- 

 meter telegraphs, capable of giving 26 signals ; he had also invented the de- 

 tector, by which injuries to the wires, whether from water, fracture, or con- 

 tact, were readily traced, an instrument which Mr. Cooke still retains in 

 constant use; and without which, indeed, an electric telegraph would be im- 

 practicable : he had also invented the alarum, on the same principle as one 

 of those in use at the present day. 



But the leading feature of the invention at this early period, and which 

 still most strongly distinguishes it from that of Messrs. Cooke and Wheat- 

 stone's telegraphs, and all others since exhibited in this country, consists in 

 this, that the telegraph did not merely send signals from one place to 

 another, but included a reciprocal system, by which a mutual communication 

 could be practically and conveniently carried on between two distant places ; 

 the requisite connexions and disconnexions being formed by pressing the 

 lingers upon keys similar in their action, and the signals being exhibited to 

 the persons sending as well as to the person receiving the communication. 

 This was and still is effected, by placing a system of keys permanently at 

 each extreme end of the circuit of wires, and by providing a draw-bridge by 

 which the circuit is completed for the electricity to pass when signals are 

 received, but which is withdrawn when the signals are to be sent. 



This united and reciprocal property is the basis of the electric telegraph, 

 and, inseparable from the practical system, and must be borne in mind when 

 the operation of these instruments is explained. Mr. Cooke has since 

 extended this instrument to any number of intermediate instruments in- 

 cluded in the same circuit — as on the Blackwall line, where there are two 

 sets, of five telegraphs each, working together — and also to the portable 

 telegraph to be carried by the trains, and temporarily introduced into the 

 permanent line of communication when required. 



By Mr. Cooke's telegraph, eight simple signals can be given, and a suffi- 

 cient number of compound ones, to admit of the 26 letters of the alphabet 

 being used ; in addition to which, by further conventional signs, those letters 

 are made to represent figures, and by a mixture of both systems, as was 

 shown, a mixed sentence, consisting of passages from a code, spelling and 

 figures, could be telegraphed together. 



Mr. Cooke first adopted the plan of laying the telegraph wires in iron 

 tubing on the Great Western Railway, and afterwards laid down a double 

 line on the Blackwall Railway, and others on the Leeds and Manchester, 

 and Edinburgh and Glasgow Railways. This plan, though perfectly suc- 

 cessful, was extremely costly and difficult to repair when injured, though by 

 aid of an instrument, the detector, less difficulty than could he supposed 

 offered itself to the detection of the injured part, though buried and out of 

 sight. More recently, Mr. Cooke invented, after extensive experiments at his 

 own residence, and carried out on the Great Western Railway, a plan of sus- 

 pending the conducting wires in the open air from lofty poles. Its leading 

 advantages are — 1st. Diminished cost; 2nd. Superior insulation; 3rd. Faci- 

 lity of repair. The old plan consisted of laying copper wires, covered with 

 cotton, and carefully varnished into smooth iron tubing — with frequent ar- 

 rangements for obtaining access to the wires, and for the facility of exami- 

 nation and repairs. The tube, after being carefully tarred, was either buried 

 in the ground or fixed on low posts, and covered with a wooden rail. This 

 plan will still be occasionally applied in conjunction with the new one, in 

 tunnels, towns, &c. 



The cost of the original plan stands nearly as follows. 



£ s. d. 

 Prepared J tube, varnished within and without, 5Jd. per foot . 115 10 

 Six copper wires, covered and varnished, at £ 6. 15s. per mile . 40 10 

 Labour and carriage, per mile . . . . . 27 



Iron fittings, boxes, &c. 12 



Tar, pitch, paint, rosin, and sundries 15 



Posts and rails, at ${d. per foot, including fixing . . 77 



The total cost of the original plan per mile . JE287 6 



To which a per centage for casualties, profit to the contractor, and the 

 price of instruments remains to be added. 



The cost by the present plan of suspension may be estimated thus. 



£ s. d. 



Drawing posts, with winding apparatus, per mile . . . 48 



Cast-iron standards, with insulators, (22 in a mile) . . . 52 



Labour in fixing and painting 12 6 



Anti-corrosion paint and tar 110 



Carriage, tools, and sundries . , 13 



Contingencies r 13 



£149 6 



Making a reduction of about 50 per cent, in favour of the present plan — 

 and a still greater advantage in favour of the permanency of the work. 



The present method of proceeding in laying down the telegraph, is first, 

 to fix firmly in the ground, at every 500 or 600 yards, strong posts of timber 



from 16 to 18 feet in height, by 8 inches square at bottom, and tapering oft' 

 to 6 by 7 inches at top, fixed into stout sills and properly strutted. Attached 

 to the heads of these posts are a number of winders for stretching the wires, 

 corresponding with the number of conducting wires to he employed ; and 

 between every two of such posts, upright wooden standards are fixed about 

 60 or 70 yards apart. A ring of iron wire, (No. 7 or 8,) which has been 

 formed by welding the short lengths in which it is made together, is then 

 placed upon a reel carried on a hand barrow, and one end being attached to 

 the winder at one draw-post, the wire is extended to the adjoining draw-post, 

 and fixed to its corresponding winder at that post; by turning the pin of 

 the ratchet wheel with a proper key, the wire is tightened to the necessary 

 degree, thus the greatest accuracy may be attained in drawing the wires up 

 till they hang perfectly parallel with each other. To sufficiently insulate the 

 wires so suspended at the point of contact with the posts, is an object of 

 indispensable importance, as the dampness of the wood during rainy weather 

 would otherwise allow the electric fluid to pass off freely into the" earth, or 

 into an adjoining wire, and thus complete the circuit without reaching the 

 distant terminus at which the telegraphic effect is to be produced. To effect 

 this object at the draw-posts, wooden boxes are employed to enclose that 

 portion of the post to which the winders are attached, and small openings 

 are left for the free passage of the wires, without risking any contact with 

 the outer box. The standards are furnished either with covers parted off 

 by an overhanging fillet between each wire, and again between the lowest 

 wire and the earth, or by a series of metal shields. An eye of metal, with a 

 slit on the upper side, forms a hook to support the wire, and to insulate the 

 wire from the hook, which might otherwise act as a conductor to any damp- 

 ness in the wood, a split quill is slipped over the wire on which it rests. 

 The whole is then carefully painted with several coats of anti-corrosion 

 paint; or asphalte varnish may be employed for the wires. When the wires 

 are to be varnished, they are unhooked from the upper ends of the stand- 

 ards, and lowered to nails temporarily fixed to receive them toward the 

 bottom of the posts. A painter furnished with a can of paint, hung on his 

 shoulder, a brush, and a piece of felt, takes each wire and rapidly coats it, 

 when it is again hooked up in its position at the top of the standard. 

 This is the simplest and cheapest method now adopted. But for long 

 distances Mr. Cooke employs earthenware or glass for his insulation, and cast 

 iron standards and posts with ash tops for drawing and suspending the con- 

 ductors, which, instead of single wires, will be strands of six or more wires 

 twisted together ; for very great distances, when very superior conducting 

 power will be needed, a copper wire will be placed in the. centre of the 

 strand, and whilst it adds but little to the weight, it will more than double 

 the conducting power thereof, the iron wire still giving the necessary strength 

 to resist tension. The relative conductive powers of copper and the softest 

 iron wire are nearly as seven to one. Various methods are adopted in pass- 

 ing under bridges, which answer the purpose of draw-posts, the winders 

 being fixed to a piece of wood partly let into the brickwork to avoid damp, 

 the greatest enemy to electric conduction. These earthenware insulations 

 are introduced between the winder and wire. Mr. Cooke also intends to use 

 caps or boxes of earthenware to surmount the iron standards. At Slough, 

 for half a mile in approaching and passing by the station, cast iron standards 

 and draw-posts are employed, the effect of which is remarkably light and 

 elegant; a line of six wires is there completed, and in crossing over a car- 

 riage shed immediately opposite to the station, the wires are stretched over 

 a length of 438 feet without any intermediate support, and so accurately are 

 they arranged, that no difference is perceivable in their parallelism: the 

 draw-posts in this instance are half a mile apart, although the line is slightly 

 curved. In passing over a station, or an accommodation road, or in crossing 

 the railway, loftier standards are employed, which abruptly lift the wires to 

 the height of 25 or 30 feet in order to clear objects passing below. In the 

 latter case lighter wires are employed, that the tension out of the direct 

 line of strain may not draw the standard from the perpendicular. 



The last advantage which need be noticed in connexion with this very 

 important step in the invention, arises from the very perfect insulation from 

 the earth. This allows of the employment of the earth as half of the con- 

 ducting circuit, without risk of the current finding a shorter course through 

 some imperfectly insulated point. For nearly two years Mr. Cooke has tried 

 this plan successfully on the Blackway Railway, and since on the Manchester 

 and Leeds Railway ; but where, as in these instances, the wires are enclosed 

 in an iron pipe, there is always danger of a contact, either partial, from a 

 few drops of moisture, or perfect, from the metals of the wire and pipe 

 touching, in which case, as before observed, the electricity takes a short 

 course instead of performing its entire circuit, and no signal is given at the 

 distant terminus, though appearing very strong at the point whence it sets 

 out. With the wires suspended in the air no such danger exists, whilst two 

 advantages spring from the employment of the earth as a conductor. 1st, 

 one wire is saved in each circuit, thus diminishing complexity and cost ; and 

 2nd, the earth acting as a great reservoir of electricity, or as some think as 

 an excellent conductor, the resistance oft'ered to the transmission of the 

 electricity is vastly diminished, and the battery is able to work through a 

 much greater distance with a smaller conducting wire. It is thus that the 

 apparatus exhibited can he made to work with two wires only. 



Mr. Whishaw then explained the model of the telegraph. Upon moving 

 the handle the poles of the battery are immediately brought in contact 

 with the extremities of two wires, one of which passes forward to make coils 

 around the galvanometer frame, in which the magnetic needles are suspended, 

 and then proceeding to the distant apparatus to make similar coils there ; 



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