it was found that owing to the unequal consumption of the carbons some were burning well, some poorly, and some going out. It was essential, therefore, to make each lamp independent of the resistance of the main circuit and of the action of the other lamps, and to have its regulating mechanism governed entirely by the resistance of its own arc. The solution of this difficult problem was the invention by Heffner von Alteneck of Germany, and his device came into use wherever throughout the world are lamps were operated. Westinghouse also improved the direct alternating system of lighting by one wire by the introduction of two conducting wires parallel to each other, and passing an interrupted or alternating current through one, thereby inducing a similar and always an alternating current through the other. Brush adopted a three-wire system; and both obtained a uniform consumption of the carbons.

In a volume like this, room exists for mention only of those inventions which burn as beacon lights on the tallest hills-and so we must now pass on to others.

66

Just as Faraday was bringing his long series of experimental researches to a close in 1856-59, and introducing the fruits of his labours into the lighthouses of England, Cyrus W. Field of New York had commenced his trials in the great scheme of an ocean cable to moor the new world alongside the old," as John Bright expressed it. After crossing the ocean from New York to England fifty times, and baffled often by the ocean, which broke his cables, and by the incredulous public of both hemispheres, who laughed at him, and by electricity, which refused to do his bidding, he at last overcame all obstacles, and in 1866 the cable two thousand miles

in length had been successfully stretched and communication perfected. To employ currents of great power, the cable insulation would have been disintegrated and finally destroyed by heat. Therefore only feeble currents could be used. But across that long distance these currents for many reasons grew still weaker. The inventor, Sir William Thomson, was at hand to provide the remedy. First, by his mirror galvanometer. A needle in the shape of a small magnet and connected to the current wires, is attached to the back of a small concave mirror having a hole in its centre; opposite the mirror is placed a graduated scale board, having slits through it, and a lighted lamp behind it. The light is thrown through the slits across to the hole at the center of the mirror and upon the needle. The feeblest imaginable current suffices to deflect the needle in one direction, which throws back the little beam of light upon it to the graduated front of the scale. When the current is reversed the needle and its shadow are deflected in the other direction, and so by a combination of right and left motions, and pauses, of the spots of light to represent letters, the message is spelled out. Second, a more expeditious instrument called the syphon recorder. In this the galvanometer needle is connected to a fine glass syphon tube conducting ink from a reservoir on to a strip of paper which is drawn under the point of the tube with a uniform motion. The irregular movements given the galvanometer needle by the varying current are clearly delineated on the paper. Or in writing very long cables the point of the syphon may not touch the paper, but the ink by electrical attraction from the paper is ejected from the syphon upon the paper in a succession of fine dots. The irregular lines of dots and

dashes were translated into words in accordance with the principles of the Morse telegraph.

An instrument was exhibited at the Centennial International Exhibition at Philadelphia in 1876, which was considered by the judges "the greatest marvel hitherto achieved by the electric telegraph." Such was the language used both by Prof. Joseph Henry and Sir Wm. Thomson, and concurred in by the other eminent judges from America, Germany, France, Austria and Switzerland. This instrument was the Telephone. It embodied, for the practical purpose of transmitting articulate speech to distances, the union of the two great forces,-sound and electricity. It consisted of a method and an apparatus. The apparatus or means consisted of an electric battery circuit, a transmitting cone placed at one end of the line into which speech and other vocal sounds were uttered, a diaphragm against which the sounds. were projected, an armature secured to or forming a part of the diaphragm, an electro-magnet loosely connected to the armature, a wire connecting this magnet with another precisely similar arrangement of magnet, armature, diaphragm, and cone, at the receiving end. When speech was uttered in the transmitter the sound vibrations were received on the diaphragm, communicated to the electricised armature, from thence by induction to the magnet and the connecting wire current, which, undulating with precisely the same form of sound vibrations, carried them in exactly the same form to the receiving magnet. They were then carried through the receiving armature and reproduced on the receiving diaphragm, with all the same characteristics of pitch, loudness and quality.

The inventor was Alexander Graham Bell, by