Radio Broadcast (May-Oct 1922)

An Evening with Dr. Alexander Graham Bell 207 But Doctor Bell was not interested in business. " It has always been that way," he told me. "After I have made a discovery and got it under way my interest in it lessens." Hardly, in fact, had Theodore N. Vail and his associates set about to make the telephone a universal servant when the inventor himself struck off into new fields. It was, as accurately as the date can at present be fixed, toward the end of the year, 1876, in which he invented the telephone, that Mr. Bell, for the first time, used the phone, instead of a galvanometer, to experiment with and to trace out the lines of the earth's potential. In these experiments, incidentally, he used a steel-band telephone, as it was then called, toclasp thephone to his ears, leaving his hands free — the first time the helmet telephone receiver was ever used. " Using two metal exploring rods — they were really stove pokers," he explained, " I set to work on Mr. Hubbard's place on the outskirts of Cambridge. 1 drove the rods into the ground. At the receiving rod 1 found that upon listening with the telephone 1 could hear a clock ticking. 1 then noted that at periodic intervals the clock would miss a tick. By means of that irregularity 1 was able to identify the clock as the time clock of the Cambridge Observatory, a half mile away. There was, I knew, a telegraph line from the Observatory to Boston, to pass the time. Using ground that was charged, with the Observatory as the centre of an imaginary circle, I was able to define concentric circles that indicated much more accurately than had been possible with a galvanometer, the lines of potential. In other words, if both of the rods were in a part of the charged ground that was to be designated as concentric circle 9, closest to the Observatory, both ends of my earth telephone circuit had the same potential, but if one were in 9 and another in 8, there would be a residual effect and I would get a sound." Later he carried these experiments on in a different direction. " First, in a vessel of water," he said, " I placed a sheet of paper. At two points of that paper were fastened two ordinary sewing needles, which were also connected with an interrupter that interrupted the circuit about 100 times a second. Then I had two needles connected with a telephone: one needle 1 fastened on the paper in the water, and the moment 1 placed the other needle in the water 1 heard a musical sound from the telephone. By moving the needle around in the water, I would strike a place where there would be no sound heard. This would be where the electric tension wi.s the same as in the needle; and by experimenting in the water you could trace out with perfect ease an equipotential line around one of the poles in the water." In July, 1877, Mr. Bell married Miss Hubbard. They went to London on their honeymoon. In London he made the classic speech on the telephone and explained and demonstrated the experiments described above to William Preece, the head of the British Post Office system, who was vastly helpful to Marconi, and others. He also experimented across the Thames. "On one side," he said, " I placed two metal plates at a distance from each other, and on the other two terminals connected with the telephone. A current was established in the telephone each time a current was established through the galvanic circuit on the opposite side, and if that current was rapidly interrupted, you would get a musical tone." On his return to America he discussed these experiments before the American Academy of Arts and Sciences in Boston, on December ii, 1878. He described his experiments, which he proceeded to develop on the Potomac. " In the experiments on the Potomac," he said, "I had two boats. In one boat we had a Leclanche battery of six elements and an interrupter for interrupting the current very ©Underwood &; Underwood Alexander Graham Bell, finding his own invention a source of annoyance, had it removed from his room in favor of a radio receiver. Mr. Bell is now 75 years old and an ardent radio enthusiast