the current to flow less freely. The sound waves which entered the ear would in this fashion throw the electric current, which flowed through the point of variable contact, into undulations in strength. It will be seen that this principle of causing the voice to control the strength of the electric current by causing it to operate upon a loose or imperfect contact, runs throughout the whole of Reis’s telephonic transmitters. In later times such pieces of mechanism for varying the strength of an electric current have been termed current-regulators.[4] It would not be inappropriate to describe the mechanism which Reis thus invented as a combination of a tympanum with an electric current-regulator, the essential principle of the electric current-regulator being the employment of a loose or imperfect contact between two parts of the conducting system, so arranged that the vibrations of the tympanum would alter the degree of contact and thereby interrupt in a corresponding degree the passage of the current.
Fig. 6.
Mr. Horkheimer, a former pupil of Reis, informs me that a much larger model of the ear was also constructed by Reis. No trace of this is, however, known.
Second Form.—Tin Tube.
The second form, a tube constructed by Reis himself, of tin, is still to be seen in the Physical cabinet of Garnier’s Institute, at Friedrichsdorf, and is shown in Fig. 7. It consists of an auditory tube a, with an embouchure representing the pinna or flap of the ear. This second apparatus shows also a great similarity with the arrangement of the ear, having the pinna or ear-flap, the auditory passage, and the drum-skin (a, b, c). Upon the bladder c there still remains some sealing-wax, by means of which a little strip of platinum, for the all-essential loose-contact that controlled the current, had formerly been cemented to the apparatus.
Fig. 7.
Third Form.—The Collar-box.
Fig. 8.
The third form, also preserved in the collection in Garnier’s Institute, is given in Fig. 8, which, with the preceding, is taken by permission from the pamphlet of the late Professor Schenk, consists of a round tin box, the upper part of which fits upon the lower precisely like the lid of a collar-box. Over this lid b, which is 15 centimetres in diameter, was formerly stretched the vibrating membrane, there being also an inner flange of metal. Into a circular aperture below opened an auditory tube a, with an embouchure representing the pinna. The precise arrangements of the contact-parts of this apparatus are not known. Mr. Horkheimer, who aided Reis in his earlier experiments, has no knowledge of this form, which he thinks was made later than June 1862. This is not improbable, as the design with horizontal membrane more nearly approaches that of the tenth form, the “Square-box” pattern.
Fourth Form.—The Bored-Block.
The instrument described by Reis in his paper “On Telephony,” in the Annual Report of the Physical Society of Frankfort-on-the-Main, for 1860–61 (see p. 50), comes next in order. The inventor’s own description of this telephone (Fig. 9) is as follows:—
Fig. 9.
“In a cube of wood, r s t u v w x, there is a conical hole a, closed at one side by the membrane b (made of the lesser intestine of the pig), upon the middle of which a little strip of platinum is cemented as a conductor [or electrode]. This is united with the binding screw p. From the binding screw n there passes likewise a thin strip of metal over the middle of the membrane, and terminates here in a little platinum wire, which stands at right-angles to the length and breadth of the strip. From the binding-screw p a conducting wire leads through the battery to a distant station.” The identical apparatus used by Reis was afterwards given by him to Professor Böttger, who later gave it to Hofrath Dr. Th. Stein, of Frankfort, from whose hands it has recently passed into the possession of the author of this work. It possesses one feature not shown in the original cut, viz. an adjusting screw, h, which, so far as the writer can learn, was put there by Reis himself. There appears no reason to doubt this, since there was an adjusting screw in Reis’s very earliest form of transmitter, the wooden ear. A section of the actual instrument is given in Fig. 10.
Fig. 10.
Fifth Form.—The Hollow Cube.
Another form, a mere variety of the preceding, is described as follows by Professor Böttger in his “Polytechnisches Notizblatt” (see p. 61):—
“A little light box, a sort of hollow cube of wood, has a large opening at its front side and a small one at the back of the opposite side. The latter is closed with a very fine membrane (of pig’s smaller intestine) which is strained stiff. A narrow springy strip of platinum foil, fixed at its outer part to the wood, touches the membrane at its middle; a second platinum strip is fastened by one of its ends to the wood at another spot, and bears at its other end a fine horizontal spike, which touches the other little platinum strip where it lies upon the membrane.”
Sixth Form.—The Wooden Cone.
Fig. 11.
Another transmitter, also a mere variety of the Fourth Form, has been described to me by Herr Peter, of Friedrichsdorf, who assisted Reis in his earlier experiments. Fig. 11 is prepared from a rough sketch furnished me by the kindness of Karl Reis. Herr Peter describes the apparatus as having been turned out of a block of wood by Reis upon his own lathe. The conical hole was identical with that of Fig. 9, but the surrounding portions of the wood were cut away, leaving a conical mouth-piece.
Seventh Form.—“Hochstift” Form.
The engraving presented below (Fig. 12) has been engraved with the utmost fidelity by Mr. J. D. Cooper, from a photograph lent to the author by Ernest Horkheimer, Esq., of Manchester, a former pupil of Reis. The original photograph was taken in 1862, having been sent by Reis in June of that year to Mr. Horkheimer, who had left for England. The photograph was taken by Reis himself with his own camera, the exposure being managed by a slight movement of the foot, actuating a pneumatic contrivance of Reis’s own invention, which was originally designed to turn over the pages of a music book at the piano. Reis is here represented as holding in his hand the telephone with which he had a few days preceding (May 11, 1862) achieved such success at his lecture before the Freies Deutsches Hochstift (Free German Institute) in Frankfort (see p. 66). This instrument was constructed by Reis, young Horkheimer assisting him in the construction. Mr. Horkheimer has very obligingly indicated from memory the form of the instrument—but dimly seen