An English electrical engineer, Mr. Ernest Oldenburg, has recently invented a new telegraphic receiver which, it is claimed, is sensitive enough to detect the most delicate impulses which a pocket battery, such as might be concealed about the person, could send out. This instrument, which is at present known as the "capilliform" receiver, is "more sensitive that the brain"; it is said to transcend previous inventions as far as Lord Kelvin's siphon recorder, which alone made submarine telegraphy practicable, surpassed its predecessors in delicacy. It depends on the fact that mercury in a vertical capillary tube-like that of a thermometer-rises and falls when an electric current is passed through it. This fact-which would be more accurately expressed by saying that the surface tension of the mercury, and therefore the shape of its meniscus, changes under the influence of an electric current-has long been known. Mr. Oldenbourg's invention consists in magnifying it and in utilizing it in a shape which enables it to be used practically as the receiving instrument of a telegraphic installation. Its peculiar value is, it is claimed, that it will respond to far smaller currents than those at present used; a mere fraction of a volt is sufficient to work it. Mr. Oldenbourg holds that it will be quite possible, with the aid of his new instrument, to make a telegraphic apparatus by which any one walking about the floor could send intelligible messages for instance to a confederate on the platform, where a "mind-reading" act is being performed, without any one else knowing about them.