“During the long-continued experiments on this subject, between 1879 and 1886, many curious phenomena came out which would be too long to describe. I found that the effect of the extra current in a coil was not increased by having an iron core as an electromagnet--the extra current was less rapid and, therefore, less effective. A similar effect of a delay was produced by Leyden jar discharges. The material of the contact-breaker of the primary current had also a great effect. Thus, if the current was broken between two, or one, piece of carbon, no effect could be perceived of aërial waves, even at short distances of a few feet. The extra current from a small coil, without iron, was as powerful as an intense spark from a secondary coil, and at that time my experiments seemed to be confined to the use of a single coil of my induction balance, charged by six Daniell cells. With higher battery power, the extra current invariably destroyed the insulation of the coils. “In December, 1879, I invited several persons to see the results then obtained. Amongst others who called on me and saw my results were:-- “December, 1879.--Mr. W. H. Preece, F.R.S.; Sir William Crookes, F.R.S.; Sir W. Robert Austen, F.R.S.; Prof. W. Gryll Adams, F.R.S.; Mr. W. Groves. “February 20, 1880.--Mr. Spottiswoode, Pres.R.S.; Prof. Huxley, F.R.S.; Sir George Gabriel Stokes, F.R.S. “November 7, 1888.--Prof. Dewar, F.R.S.; Mr. Lennox, Royal Institution. “They all saw experiments upon aërial transmission, as already described, by means of the extra current produced from a small coil and received upon a semi-metallic microphone, the results being heard upon a telephone in connection with the receiving microphone. The transmitter and receiver were in different rooms, about 60 ft. apart. After trying successfully all distances allowed in my residence in Portland-street, my usual method was to put the transmitter in operation and walk up and down Great Portland-street with the receiver in my hand, with the telephone to the ear. “The sounds seemed to slightly increase for a distance of 60 yards, then gradually diminish, until at 500 yards I could no longer with certainty hear the transmitted signals. What struck me as remarkable was that, opposite certain houses, I could hear better, whilst at others the signals could hardly be perceived. Hertz’s discovery of nodal points in reflected waves (in 1887-9) has explained to me what was then considered a mystery.