<P> Aperture card mounted microfilm is roughly 3% of the size and space of conventional paper or vellum engineering drawings . Some military contracts around 1980 began to specify digital storage of engineering and maintenance data because the expenses were even lower than microfilm, but these programs are now finding it difficult to purchase new readers for the old formats . </P> <P> Microfilm first saw military use during the Franco - Prussian War of 1870--71 . During the Siege of Paris, the only way for the provincial government in Tours to communicate with Paris was by pigeon post . As the pigeons could not carry paper dispatches, the Tours government turned to microfilm . Using a microphotography unit evacuated from Paris before the siege, clerks in Tours photographed paper dispatches and compressed them to microfilm, which were carried by homing pigeons into Paris and projected by magic lantern while clerks copied the dispatches onto paper . </P> <P> Additionally, the US Victory Mail, and the British "Airgraph" system it was based on, were used for delivering mail between those at home and troops serving overseas during World War II . The systems worked by photographing large amounts of censored mail reduced to thumb - nail size onto reels of microfilm, which weighed much less than the originals would have . The film reels were shipped by priority air freight to and from the home fronts, sent to their prescribed destinations for enlarging at receiving stations near the recipients, and printed out on lightweight photo paper . These facsimiles of the letter - sheets were reproduced about one - quarter the original size and the miniature mails were then delivered to the addressee . Use of these microfilm systems saved significant volumes of cargo capacity needed for vital war supplies . An additional benefit was that the small, lightweight reels of microfilm were almost always transported by air, and as such were delivered much more quickly than any surface mail service could have managed . </P> <P> Libraries began using microfilm in the mid-20th century as a preservation strategy for deteriorating newspaper collections . Books and newspapers that were deemed in danger of decay could be preserved on film and thus access and use could be increased . Microfilming was also a space - saving measure . In his 1945 book, The Scholar and the Future of the Research Library, Fremont Rider calculated that research libraries were doubling in space every sixteen years . His suggested solution was microfilming, specifically with his invention, the microcard . Once items were put onto film, they could be removed from circulation and additional shelf space would be made available for rapidly expanding collections . The microcard was superseded by microfiche . By the 1960s, microfilming had become standard policy . </P>

Which of the following would typically not form part of definitive media library