The Jacquard Loom was a mechanical loom for cloth weaving, first demonstrated by Joseph Marie Jacquard in 1801. It used a chain of punched cards laced together to allow the loom to create complex patterns.
Any number of the cards could be chained together into a continuous sequence, with each card corresponding to one row of the design. Each position on the card corresponds to a ‘Bolus’ hook which can either be raised or stopped dependent on whether the hole is punched out of the position on the card or not. The hook raises or lowers the harness, which carries and guides the warp thread so that the weft will either lie above or below it.
Modern Jacquard looms are controlled by computers in place of the original punched cards, and can have thousands of hooks.
Charles Babbage was aware of Jacquard loom cards, and planned to use cards to store programs in his Analytical engine, first described in 1837. Later in the 19th Century, Herman Hollerith used the idea of storing information on cards to create the punched card tabulating machine which he used to input data for the 1890 US Census.
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The magic lantern was an early type of image projector, developed in the 17th century.
It used a concave mirror behind a light source to direct as much of the light as possible through a small rectangular sheet of glass – the magic lantern slide – on which was the painted or photographic image to be projected – and onward into a lens at the front. The lens was adjusted to focus at the distance of the projection screen or wall.
Initially, candles or oil lamps were used, producing very dim projections. Improvements in lighting took the form of the Argand lamp from the 1790s, limelight in the 1820s, electric arc light in the 1860s and finally the incandescent electric lamp.
The magic lantern could project moving images by the use of various types of mechanical slide, which could be over a foot long at times and could contain gears cranks and pulleys. Even in still slides there was little standardisation. Peck and Snyder, a company with great influence in the magic lantern industry, sold slides measuring 4.5 by 7 inches. ‘English pattern’ slides were 3.5 by 3.5 inches, ‘French pattern slides’ were 3.25 by 4 inches, and the ‘standard European size’ was 3.25 by 3.25 inches.
The art of projection reached a high-point in the 1870-1880 period, and the magic lantern played a very important part in Victorian society. Temperance and religious lectures were given but the lantern was also used in education, for the demonstration of scientific principles, to relay the latest news of world events, and to create ‘phantasmagoria’ shows. By this time, images were being transferred to slides by photographic means, and then coloured by hand. Lanterns of this time could have up to four projection tubes.
With the advent of cinema the days of the big lantern shows were numbered, but magic lanterns were still used in schools and institutes, and photographic and printed slides were still being manufactured in the 1940s.
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Punched tape or perforated tape was an early form of data storage, developed from interlinked cards such as those used on the Jacquard loom.
In 1846, punched tape was used for sending telegrams. Operators could type a message to the paper tape, and then sent the message at the maximum line speed from the tape.
Various encoding schemes were used over time, beginning with Baudot with 5 holes, and culminating in ASCII. A row of narrower holes served to feed the tape.
When the first minicomputers were being released, manufacturers turned to the existing mass-produced ASCII teleprinters and punched tape became a popular medium for low cost minicomputer data and program storage. Punched tape and punched cards became the primary means of mass storage for computers in the 1960s.
In the 1970s, computer-aided manufacturing equipment often used paper tape, as paper tape readers were smaller and much less expensive than punched card or magnetic tape readers. Premium black waxed and lubricated long-fibre papers, and Mylar film tape were invented so that production tapes for these machines would last longer.
Punched tape had a low information density and took a long time to load, and more than a few dozen kilobytes are impractical to handle in punched tape format. Unlike magnetic tape though, punched tape can be read decades later if acid-free paper or Mylar film was used, and can even be decoded visually if necessary.
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Microfilm is 16 or 35mm film, usually unperforated, containing microreproductions (normally about one twenty-fifth of the original size) of images such as documents. Images are usually provided as black and white negatives, but positive images and colour are also used.
The standard length for roll film is 30.48 m (100 ft)for 35mm rolls, and 100 ft, 130 ft and 215 feet for 16mm rolls. One roll of 35 mm film may carry 600 images of large engineering drawings or 800 images of broadsheet newspaper pages. 16 mm film may carry 2,400 images of letter sized images as a single stream of micro images along the film set so that lines of text are parallel to the sides of the film or 10,000 small documents, perhaps cheques or betting slips, with both sides of the originals set side by side on the film.
Microphotography was first used in 1839 by John Benjamin Dancer, and microfilm saw military use in the Franco-Prussian War of 1870–71 as a means of allowing pigeons to carry dispatches in compressed form.
It was first used commercially in the 1920s. New York City banker George McCarthy was issued a patent in 1925 for his Checkograph machine, designed to make micrographic copies of cancelled cheques. In 1928, the Eastman Kodak Company bought McCarthy’s invention and began marketing cheque microfilming devices under its Recordak division.
Early microfilms (to the 1930s) were printed on nitrate film, which is explosive and flammable. From the late 1930s to the 1980s, microfilms were usually printed on a cellulose acetate base, which is prone to tears, vinegar syndrome, and redox blemishes. Preservation standard microfilms use the silver halide process, creating silver images in hard gelatin emulsion on a polyester base. With appropriate storage conditions, this film has a life expectancy of 500 years.
Unlike digital media, the format requires no software to decode the data stored thereon, but the images are usually too small to read with the naked eye and requires magnification to be read.
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