cellar under President Low’s office at Columbia College, and that too in spite of the heavenly beauty of the views which on my walks met me on every turn of the winding roads which lead up to the wonderful passes of Switzerland. I was most anxious to submit my theory to an experimental test. When our tour in Switzerland was finished I had every detail of the proposed experimental tests worked out in my head, and yet my good wife never accused me of being absent-minded. In less than a year from that time I had finished my first rough test, and was preparing for a more elaborate investigation when the discovery of the X-ray was announced, at the very end of 1895, and I, like everybody else, dropped everything and eagerly sought information about this wonderful discovery. It was the work I dropped then which I took up again after my recovery from the breakdown of 1896. Now what is the invention which occurred to me first on my walk to the Furka pass in Switzerland in the summer of 1894? A bit of scientific history is connected with it, which I shall tell here briefly: A vibrating motion of electricity at one end of a long wire is propagated along the wire in much the same way as the vibratory motion of a rope or string is propagated from one of its terminals to the other. This propagation of electrical motion from one end of a long conducting wire to the other was first investigated by Professor William Thomson, the late Lord Kelvin, of the University of Glasgow, in 1855, when the first Atlantic cable was projected. He worked out the problem for electrical signalling over a submarine cable, and three years later Kirchhoff, who was one of my teachers in Berlin, worked it out for telegraphic signalling over land-lines stretched over poles. When telephony was invented in 1876, there was, of course, a demand for a mathematical theory of telephonic transmission over long conducting wires. He who understood Thomson’s and Kirchhoff’s work could experience no serious difficulty in working it out. Vaschy, a Frenchman, and Heaviside, an Englishman, were the first to work it out; they did it in the chronological order just indicated, Vaschy leading Heaviside by about two years. They both observed that just as in cable and land-line telegraphy so also in telephony the reduction of the transmitted electrical force was the smaller the larger the so-called inductance of the transmitting wire. Many people believe that this observation was an important discovery; I never thought so, because I believed that Thomson’s and Kirchhoff’s work made that observation obvious. But, however that may be, the observation was made by Vaschy two years before it was made by Heaviside, and neither one nor the other saw in it a special case of a general physical principle, which the Allies appreciated much during the World War in their struggles against the submarines. I shall describe it briefly: