Science in the industrial world Author:Henry Smith Williams Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: larly useful where the same messages are to be sent to a number of different places, as the perforated strip of paper can be made in multiples at a single punchi... more »ng. Many different types of telegraph recorders have been invented since the time of Morse's first instrument, several of these being the experimental inventions of Morse himself. The principles involved in these recorders have been both chemical and mechanical, the mechanical ones, as a rule, predominating. Practical chemical recorders are used, however, utilizing the well-known fact of chemical decomposition by the electric current. For example, if a strip of paper is saturated with some chemical which is easily decomposed by electricity, and in this decomposition changes color, the pressure of an electrical needle upon this strip of paper will produce a mark. If the strip is arranged on rolls which pass it beneath the position of the needle at a uniform rate of speed, dashes and dots may be made by the needle's contact with the paper for a longer or shorter time. This method is found to be entirely practical, and the principle is utilized in many recording devices. It is quite beyond the scope of this work to go into details of the hundreds of telegraphic devices, for signaling, etc., the numbers of which are being multiplied almost daily, and which have become practical necessities in civilized communities. But it is interesting to remember that such widely divergent mechanisms as the dial-signaling apparatus with which the captain of the ocean liner communicates his commands to the engineer far below in the engine-room, the Atlanticcable with which Europe communicates instantly with America, the button that explodes a submarine mine, and the familiar electric door-bell and call-button, are all developments of Mo...« less