On Monday, while the Mechanical Section of the British Association
were discussing the means of using the electric light in coal mines, Mr. Swan, inventor of the " Swan lamp," made a remarkable statement. He produced an electric lamp of two-candle power, quite detached from any wire, and port- able, which could be kept lighted for six hours by a 2-cell Faure secondary battery. The weight of the battery would not exceed 10 lb., and to charge it afresh, it would only be necessary " to place it for a time in connection with the wires of a dynamo near the pit's mouth." The battery and lamp need never leave the pit. Sir J. Hawkshaw greatly approved this lamp, and well lie might. 'The germ of a portable and handy electric lamp, unconnected with any wire, and fed at intervals only as an oil lamp is, must lie in that rude specimen shown. A portable electric lamp with a strong light would be one of the greatest inventions of our day, and make a hundred enterprises possible which are now avoided. It would materially alter, to begin with, all the conditions of mining, tunnel-making, and work in sewers or -under water; while it would, if reasonably cheap, be the greatest of modern contributions to domestic comfort. What is wanted is a portable light which will burn a week and can then be recharged at a distance, so that a private house need not be .connected with any system, and fitters need not be summoned.
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