From very thin ferrotype plate cut a piece two inches square, and at the middle of it attach the other carbon button by means of a small rivet which you can make from a piece of copper wire. Or a very small brass machine screw may be passed through the button and plate; then gently tapped at the face of the plate to rivet it fast, as shown at E. Lay the block down flat and partly fill the cavity with carbon granules until the button is covered. Do not fill up to the top of the hole. Over this lay the disk (D), so that the carbon button at the under side of it will fit in the top part of the hole between the sides of felt or flannel. Make the disk fast to the block (A) with small pins made by clipping ordinary pins in half and filing the ends. A slim bolt (G) is passed through the block (A), and a wire terminal is caught under a nut and between a washer at the back of the block, as described for F. The japan or lacquer must be scraped away from the disk (D) where the bolt-head touches it, so that perfect electrical contact will be the result. A small tin funnel is cut and made fast to the face-plate (B), or if an electrical supply-house is at hand a mouth-piece of hard rubber or composition may be had for a few cents. The block (B) is then screwed fast to A, forming the transmitter shown at Fig. 9. When this transmitter stands in a vertical position the granules, or small particles of carbon, drop down between the buttons of carbon, packing closely at the bottom of the cavity. At the middle they are loosely placed, and at the top there are none. As the high or low vibrations of the voice fall on the disk (D) they act accordingly on the carbon granules, which in turn conduct the vibrations to the rear carbon button, and, by the aid of electricity reproduce the same sound, in high or low tone, through the receiver at the other end of a line. This improved transmitter makes it possible to talk in a moderate tone of voice over distances up to one thousand miles, while with the old form of the instrument it was necessary to talk very loud in order to be heard only a few miles away. Where a portable apparatus is desired, this block may be attached to a box or an upright staff. This transmitter will not work when on its back or so that the funnel is on top, because the particles of carbon would settle on the rear button and not touch the front one. It is essential that the carbon grains should touch both buttons at the same time, and at the lower part of the cavity they should lie quite solid. It is not necessary, however, to pack it in, for the vibratory action of the voice, or other sounds, will cause the particles to adjust themselves and settle in a compact mass. Another Form of Transmitter In Fig. 11 another style of transmitter is shown. It is assembled on the front of a box. This front or cover swings on hinges, and can be opened so that the mechanism in the interior of the box may be gotten at easily.