290

BRETT’S WIRE AXE IRON CABLES—ELECTRIC TELEGRAPHS.

[Class X.

the letters may be printed at a greater speed than a well-practised person could write them, and that a clerk, aftersome experience, might manipulate upon the linger key-board upwards of 150 letters per minute.

Mr. Brett has also exhibited a specimen of the line usedin the first experiment, across the Dover Strait , afterhaving been submerged in very deep water for more thansix months, and is part of the same wire through whichthe first galvanic current was transmitted from the coastof England to that of France . The experimental linewas formed of a single copper wire, insulated by alayer of gutta-percha about five-eighths of an inch indiameter.

Mr. Brett also exhibits a specimen of wire cable. Thisis a portion of a permanent line, now being laid down

from the South Foreland to Sangatte, near Calais ; thecore of the cable is formed of four copper wires (No. 16),each of which is insulated and covered with two separatelayers of gutta-percha. As in the experimental wire, thetightening of the line elongated it to a considerable extent,and caused the gutta-percha to divide, so destroying theperfect insulation of the wire; it was therefore resolvedto obviate this source of failure by twisting the four wirestogether spirally, before encasing them in the hempenyarn, well saturated with tar and bituminous compounds,with which they are completely enveloped. The corethus formed, is protected by ten galvanized iron wires(No. 10 gauge) twisted together, the whole composinga cable 1^ inches in diameter, as shown in the annexedcut.

Mr. Brett also exhibits a vertebrated iron tubular cable.This is designed to protect a cable of submarine tele-graphic wires, when situated near the sca-eoast, fromsustaining damage by anchors, or by casualties likely to

occur when situated in the vicinity of shipping, and maybe made of great strength, and of considerable curvature,without either damage or derangement, as in the followingfigure. .

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One of the iron cables exhibited, is constructed with | a greater degree of strength in dangerous situations, asthe addition of a chain of links, for the purpose of giving | shown in the annexed figure :—

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A Council Medal was awarded to Mr. Brett,

Bain (No. 434, p. 460) has exhibited an electro-chemical telegraph, depending, like that of Mr. Bake-well’s, on the development at a distance of the chemicaleffects of electricity. The effect produced is the pre-cipitation of Prussian blue on paper, duly prepared byimpregnation with prussiate of potash and weak acid, onthe contact of a steel pointer, at the signal station ; thiscontact being determined by the attraction of an electro-magnet on the arm which carries it. The breaking andrenewal of contact at the station of departure, is effectedby the interposition of a baud of paper, drawn uniformlyalong by clock-work, and punched out in holes and slitsof different lengths, which allow of more or less pro-longed contacts, in conformity with a conventionalalphabet. At the station of reception, a large circulardisc of the prepared paper is made to revolve uniformly,by simultaneous clock-work, while the iron point, whichon every renewal is pressed into contact with the paper, iscarried to or from the centre current uniformly by a

scr£w motion, along a line to the centre of the disc, andleaves traces on the paper as it passes beneath it, inPrussian blue corresponding to the stamped line in theoriginal paper baud, and which may therefore be read offat leisure ; other preparations, such as that of starch withiodine, potash, See., may be used for preparing the paper.There is much mechanical ingenuity and skill displayedin every part of this apparatus.

A Council Medal was awarded to Mr. Bain.

Bakewell (No. 433, pp. 459-60) exhibits a copyingelectric telegraph, which is fully described in the Illus-trated Catalogue, with the method of use, excepting themethod of transmitting invisible messages, which iseffected by using paper moistened with diluted acidalone, when a deposition of iron from the steel point ismade on the paper without any mark, the writing beingsubsequently made visible by a solution of the prussiateof potass.

A Council Medal was awarded to Mr. Bakewell.

Walker (No. 430, pp. 458, 459) has exhibited a mode