Abstract
A SERIES of experiments was made last week at Sheerness, with a view of ascertaining the applicability of Siemens' dynamo-electric light to torpedo services in time of war. This scientific combination is produced, as its name signifies, by the application of excessively rapid motion generated from the flywheel of a steam-engine to a very powerful set of ordinary galvanic “coils” in connection with soft-iron magnets. The leather strap from a four-horse power engine, encircling a small gunmetal pinion, causes it to revolve with the extreme velocity of 1,600 revolutions per minute, inducing motion in an electric “bobbin” at the side of an apparatus consisting of several sets of strong insulated coils. A stream of electricity consequently passes through them. This stream is conducted to a second series of coils, larger and more powerful than the first, which are also in combination with a pinion revolving 800 times per minute, thus intensifying the stream as it passes through them to a very considerable degree. Both negative and positive currents are now alternately given off from another “bobbin” at the side of the second series of magnetic coils, to the train of insulated wires, which conveys them to the position from which the dynamoelectric light is to be exhibited. Here there is a delicately contrived apparatus for containing the carbon points, between which the light is to be generated, adjusted at the top of a tripod somewhat similar in construction to that of a surveying instrument. At the back of the two carbon points, and “slotted” vertically to admit of their holders passing through it, is a concave reflector of white polished metal, which collects the rays of light into a focus, and transmits them in any required direction by means of an adjusting hand wheel below. A minute aperture in the centre of the reflector, precisely behind the junction of the two carbon points, throws a representation of the flame upon a piece of opal glass in a frame fixed at the back of the reflector; and through the agency of another small hand wheel which causes the carbon points to approach or recede from each other, the flame can be reduced or intensified at pleasure, by simply turning the wheel, care being taken at the same time to keep a watchful eye upon the picture produced, as the withdrawing of the points to too great a distance from each other will extinguish the light. It should have been remarked before that ample means are taken by lubricating the electrical apparatus to counteract the evil effects which might otherwise arise from the excessive friction consequent on the rapidity of motion in the several parts.
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Siemens' Dynamo-Electric Light * . Nature 5, 172 (1871). https://doi.org/10.1038/005172a0
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DOI: https://doi.org/10.1038/005172a0