The final form adopted by Reis for his Reproducing-apparatus is that commonly known as the Knitting-needle Receiver. It differs only from the first form in that the needle and its surrounding spiral no longer stand upright on a violin, but lie horizontally upon a rectangular sounding-box of thin pine wood. The coil of silk-covered copper wire is wound upon a light wooden bobbin, instead of being twisted round the needle itself. Two wooden bridges stand upon the sounding-box, and through these pass the protruding ends of the needle, whilst an upper box or lid, hinged to the lower at the back, is added above. Figs. 22 and 23 show this form, the former being reproduced from Reis’s own Prospectus (see p. 85), the latter being from Müller-Pouillet’s ‘Text-book of Physics’ (see p. 95). Herr Albert, mechanician, of Frankfort, who made and sold the Reis telephones, says that the upper box was added at his suggestion. Originally it was so constructed (see Fig. 22), that when closed it pressed upon the steel needle. In the instruments of later date, the notches which fitted over the needle were cut so deeply (see Fig. 23), that the lid did not press upon the wire. Reis’s own instructions are (see p. 86) that the sound is intensified by firmly pressing the lid against the needle, as was done occasionally by the listeners who pressed their ears against the lid in order to hear more distinctly. The little key seen at the end of the sounding-box, in Fig. 22, was used for interrupting the current and so to telegraph back signals to the transmitter. FOOTNOTES: [3] Dr. Messel, F.C.S., a former pupil of Reis, and an eye-witness of his early experiments, makes, in a letter to Professor W. F. Barrett, the following very interesting statement: “The original telephone was of a most primitive nature. The transmitting instrument was a bung of a beer-barrel hollowed out, and a cone formed in this way was closed with the skin of a German sausage, which did service as a membrane. To this was fixed with a drop of sealing-wax a little strip of platinum corresponding to the hammer of the ear, and which closed or opened the electric circuit, precisely as in the instruments of a later date. The receiving instrument was a knitting needle surrounded with a coil of wire and placed on a violin to serve as a sounding board. It astonished every one quite as much as the more perfect instruments of Bell now do. The instrument I have described has now passed into the hands of the Telegraph Department of the German Government.” [The instrument now in the museum of the Reichs Post-Amt in Berlin is not this, but is the first of the “Improved” Telephones described later by Reis in his “Prospectus” (see p. 85), and is stamped “Philipp Reis,” “1863,” “No. 1.”] S.P.T. [4] Or sometimes “tension-regulators,” though the latter term is acknowledged by most competent electricians to be indescriptive and open to objection.