[1] An autograph letter of Philipp Reis to Mr. W. Ladd, the well-known instrument maker of Beak Street, London, describing his telephone, is still preserved, and is now in possession of the Society of Telegraph Engineers and Electricians of London. It is reproduced at p. 81. [2] As to the difference in quality of the instruments, see the testimony of the maker, Albert of Frankfort, on p. 44. Prof. Pisko (see p. 101) seems to have had a peculiarly imperfect instrument. CHAPTER II. THE INVENTOR’S APPARATUS. 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._ 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. [Illustration: Fig. 2.] [Illustration: Fig. 3.] [Illustration: Fig. 4.] [Illustration: Fig. 5.]