Two Danish engineers, Mr. Johnsen and Mr. Rahbek, described, in
a lecture in London last week, the application of a principle In electricity which may have important consequences. A weak current applied to two solid substances, the one a good conductor and the other a bad conductor, makes them adhere closely. A metal disc placed on a lithographic stone, for example, clings tightly to the stone as soon as the current is passed through it, and releases the stone when the current ceases. The lecturers showed that the principle could be applied to produce a cheap electric bell, worked by a very small current, or an improved telegraphic receiver, era loud-speaking telephone. They exhibited a stringless violin, against which was placed an agate cylinder rotating and rubbing against a piece of metal. This violin reproduced a tune played on a distant violin.
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