14, save modern reproductions from Legat’s drawing, has been found. The instrument held by Reis in his hand in the photograph (Fig. 12) is so strikingly like the form described by Legat, that it furnishes an additional reason for accepting Legat’s statement that this transmitter really is Reis’s invention. [Illustration: Fig. 15.] [Illustration: Fig. 16.] _Ninth Form._--TRANSITIONAL FORM. Our knowledge of this form is derived solely from information and sketches supplied by Mr. E. Horkheimer, who assisted Reis in its construction. Figs. 15 and 16 are engraved after Mr. Horkheimer’s sketches. The conical mouthpiece was of wood: the contact pieces of platinum. The point _c_ was attached to a springy slip of brass, _g_, fixed across the wooden box; and the adjusting-screw, _h_, served to regulate the degree of initial pressure at the point of contact which controlled the current. _Tenth Form._--THE SQUARE BOX. [Illustration: Fig. 17.] [Illustration: Fig. 18.] The last form of Reis’s Transmitter is that which has become best known, being the only one (except Fig. 9) which found its way into the market. It is here named, for the sake of distinction, as the “Square Box” pattern. It consisted of a square wooden box, having a hinged lid. Fig. 17 is reproduced from Reis’s “Prospectus” (see page 85), whilst Fig. 18 is taken from Prof. Schenk’s biographical pamphlet. In this instrument the idea of the human ear is still carried out. The tin funnel, with its flaring embouchure, still represents the auditory tube and pinna. The tympanum, no longer at the very end of the tube, is strained across a circular aperture in the lid. Upon it rests the strip of platinum foil which serves as an electrode, and resting in loose contact with this lies the little angular piece of metal which Reis called the “Hämmerchen.” Above all lay a circular glass disk (a cover to keep out the dust), which was removed when the instrument was used. So sensitive did this form prove itself that it was found unnecessary to speak right into the mouthpiece, and the speaker in practice talked or sang with his mouth at some little distance vertically above the instrument; a method which had the advantage of not so soon relaxing the membrane by the moisture of the breath. The figures show also the auxiliary apparatus attached at the side, consisting of a key for interrupting the circuit (added at first to enable the experimenters to single out the “galvanic tones” from the reproduced tones, and later applied, as Reis explains in his “Prospectus,” on page 87), and an electro-magnet to serve as a “call,” by which the listener at the other end could signal back to the transmitter.