Fig. 1.

       Monument to Philipp Reis in the Cemetery at Friedrichsdorf.

CHAPTER II.

       THE INVENTOR’S APPARATUS.

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      In describing the various forms successively given by the inventor to his apparatus, as he progressed, from the earliest to the latest, it will be convenient to divide them into two groups, viz. the Transmitters and the Receivers.

A.—Reis’s Transmitters.

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      So far as can be learned, Reis constructed transmitters in some ten or twelve different forms. The complete series in this course of evolution does not now exist, but the principal forms still remain and will be described in their historical order. Theoretically, the last was no more perfect than the first, and they all embody the same fundamental idea: they only differ in the mechanical means of carrying out to a greater or less degree of perfection the one common principle of imitating the mechanism of the human ear, and applying that mechanism to affect or control a current of electricity by varying the degree of contact at a loose joint in the circuit.

      First Form.—The Model Ear.

      Naturally enough the inventor of the Telephone began with crude and primitive[3] apparatus. The earliest form of telephone-transmitter now extant, was a rough model of the human ear carved in oak wood, and of the natural size, as shown in Figs. 2, 3, 4, & 5.

      Fig. 2.

      Fig. 3.

      Fig. 4.

      Fig. 5.

      The end of the aperture a was closed by a thin membrane b, in imitation of the human tympanum. Against the centre of the tympanum rested the lower end of a little curved lever c d, of platinum wire, which represented the “hammer” bone of the human ear. This curved lever was attached to the membrane by a minute drop of sealing-wax, so that it followed every motion of the same. It was pivoted near its centre by being soldered to a short cross-wire which served as an axis; this axis passing on either side through a hole in a bent strip of tin-plate screwed to the back of the wooden ear. The upper end of the curved lever rested in loose contact against the upper end g of a vertical spring, about one inch long, also of tin-plate, bearing at its summit a slender and resilient strip of platinum foil. An adjusting-screw, h, served to regulate the degree of contact between the vertical spring and the curved lever. The conducting-wires by which the current of electricity entered and left the apparatus were connected to the screws by which the two strips of tin-plate were fixed to the ear. In order to make sure that the current from the upper support of tin should reach the curved lever, another strip of platinum foil was soldered on the side of the former, and rested lightly against the end of the wire-axis, as shown in magnified detail in Fig. 6. If now any words or sounds of any kind were uttered in front of the ear the membrane was thereby set into vibrations, as in the human ear. The little curved lever took up these motions precisely as the “hammer”-bone of the human ear does; and, like the “hammer”-bone, transferred them to that with which it was in contact. The result was that the contact of the upper end of the lever was caused to vary. With every rarefaction of the air the membrane moved forward and the upper end of the little lever moved backward and pressed more firmly than before against the spring, making better contact and allowing a stronger current to flow. At every condensation of the air the membrane moved backwards and the upper end of the lever moved forward so as to press less strongly than before against the spring, thereby making a less complete contact than before, and by thus