In 1840 Mr. Bain, in conjunction with Mr. Barwise, patented a clock which was to be set in motion by electricity ; and in the next following year ho brought forward a new electric printing telegraph. The essential principles of this telegraph are two. First, the employment of type, mounted on the periphery of a disc Or wheel, capable of ving with its edge carrying the type very near to a cylinder covered with -white paper, between which and the type-wheel a piece of trans ferring paper or riband is placed; the cylinder has a small movement in a spiral direction communicated to it, after each impression of a signal. The second principle is that of the use of two clocks at the two communicating stations, to rotate the type-wheels with a uni form motion. These clocks, having been ad justed to exactly the same rate, and being started from the same signal, would bring continually, at each station, similar type oppo site to the paper cylinders at the same mo ment. A hand or index revolving on a dial in front of the machine, at the same rate as the type-wheel, indicates to the operator the sig nals which are successively in a position ready for printing in his own instrument, and there fore, if the clocks go accurately together, in a similar position in his correspondent's instru ment.
In 1842 Mr. Bain patented his proposed plan for working an electric telegraph with a peculiar form of battery. At one end of the line he buried in moist earth a largo plate of zinc, and at the other end a plate of copper, iron, or other substance, such as coke or char coal, which might act the part of a negative plate to the zinc. Then on connecting these distant plates with a wire insulated from the earth, a current of electricity would constantly pass from the one plate to the other. This system has been found insuffitient at long distances.
In 1843 Mr. Cooke specified his patent for the Mode of insulating the wires by suspend ing them in the air upon posts or standards of Weed eriron; the wires not comihg in actual Contact with any part of the standard, but passing through rings of porcelain or earthen ware. The standards are useally fixed at from forty to sixty yards asunder, and at each quarter of a mile a stouter post is placed, to bear the winding or straining apparatus. The intermediate posts within each quarter of a mile merely supported the wire, without re ference to its tension, which depended solely on the winding posts. Instead of the copper wires hitherto employed, iron wires of a larger size were then used. Before this period the wires had been placed in iron tubes buried beneath the ground ; but this new form of arrangement MO deemed an improvement, and has since been generally acted on in this country.
Since the year last named, the progress of the electro-telegraphic system has been ex ceedingly rapid. In 1846 an Electric Tele
graph Company was formed, by whom the patent rights of Messrs. Cooke and Wheat. stone, and some of those of Mr. Baits, were purchased. It is this company which has carried out the greatest part of what has been recently effected in Great Britain. Nearly all the principal railways, except the Great Western, have: had lines of telegraphic wire laid by it. A modification of Cooke and Wheat-' stone's arrangements is generally employed ; but the company also possesses a remarkable printing or rather registering telegraph in vented by Mr. Main. A long strip of paper has small Wee stamped in it by means of a machine, each hole or group of holes repre senting a particular letter. This paper is coiled on a wooden roller, from whence it passes to a metal roller, where metallic points act upon it. The arrangement Of the me chanism is such, that when the metallic points touch the metal of the roller, through the holes in the paper, a galvanic circuit is corn; pleted ; but when the points touch the paper itself, the circuit is stopped ; and this rapid alternation is made to indicate signals. There is also a recipient apparatus, in which the strip of paper employed has been first soaked in diluted sulphuric acid, and then in a solution' of prussiate of potash., Two metallic points: press on this paper ; and when a galvanie =rent is passing through these points, discolour the chemically-prepared paper, and leave a number of dark spots. upon bite when no current is passing, no is produced. By an ingenious arratigment of mechanism, the recipient apparatus at the' end of the telegraphic wire marks with its dark spots the signals which are conveyed the transmitting apparatus at the other end.
In the form which the English teIegraphici systeM has now aseunaed, all the stetiotesare placed in connection with the central office it Lothbury. At this office are departments fo transmitting messages to and receiving mes sages from almost all parts of the kingdom There are several rooms, each of which ha its own electric clock, showing Greenwicl time, and its own electro-telegraphic machine Wires pass from the machines to the grea hall, and from the hall to the outside of thi building, whence they pass under the pave merits of the London streets to the great rail way termini at Euston Square, Shoreditch London Bridge, Waterloo Road, arc., as well a: to the Admiralty and one or two other Govern ment establishments. Along the lines of rail way the telegraphic wires and apparatus an so arranged as to be available both for the railway company's own purposes, and for commercial purposes in general ; and a sys tern has been formed whereby information of a commercial character is regularly transmit, ted to and from the great centres of industry and commerce.