Heroes of the Telegraph

The wax is moulded into the form of a tube or hollow cylinder, usually 4 1/4 inches long by 2 inches in diameter, and 1/8 inch thick. Such a size is capable of taking a thousand words on its surface along a delicate spiral trace; and by paring off one record after another can be used fifteen times. There are a hundred or more lines of the trace in the width of an inch, and they are hardly visible to the naked eye. Only with a magnifying glass can the undulations caused by the vibrating stylus be distinguished. This tube of wax is filed upon a metal barrel like a sleeve, and the barrel, which forms part of a horizontal spindle, is rotated by means of a silent electro-motor, controlled by a very sensitive governor. A motion of translation is also given to the barrel as it revolves, so that the marking stylus held over it describes a spiral path upon its surface. In front of the wax two small metal tympanums are supported, each carrying a fine needle point or stylus on its under centre. One of these is the recording diaphragm, which prints the sounds in the first place; the other is the reproducing diaphragm, which emits the sounds recorded on the wax. They are used, one at a time, as the machine is required, to take down or to render back a phonographic message.