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An Encyclopedia of the History of Technology part 71

An Encyclopedia of the History of Technology part 71. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART FOUR COMMUNICATION AND CALCULATION the three-colour theory to photography and with that and the invention of the half-tone screen the way was clear to convince the eye that it sees the range of colours in the original when what it really sees is a collection of dots of yellow magenta red and cyan blue ink known as process colours of varying intensities. A fourth colour was added later black to give greater depth of tone. The first example of three-colour printing was exhibited by F.E.Ives at Philadelphia in 1885 and it became a practical proposition from 1892. It could be applied to any of the three printing processes. Four plates are made by photographing the coloured original four times through a halftone screen using a different coloured filter each time blue green red and yellow for printing successively in yellow magenta cyan and black ink. More recently the orthodox process camera began to be replaced by more sophisticated equipment that is by the photoscanner. It was in 1937 that Alexander Murray working for Eastman Kodak built the first scanner in which a scanning head picked up light from a coloured transparency and a photomultiplier converted this into electronic signals. From these various kinds of output can be derived according to the printing process. Laser light is now used to expose the output film. OFFICE PRINTING A kind of typesetting has been carried out for over a century by nonprinting operatives on the typewriter. Ideas for writing machines go back to the eighteenth century and many designs were conceived including some that resulted in embossed marks on paper to enable the blind to read by touch. The first commercially successful typewriter was evolved by the American inventors Christopher Latham Sholes and Carlos Glidden to type letters on to paper. They persuaded the firm of gunmakers Remington to manufacture it and the job was given to their sewing machine division. Hence the first practical typewriter when it appeared in 1873 bore a