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Cave paintings are a type of parietal art (which category also includes petroglyphs, or engravings), found on the wall or ceilings of caves. The term usually implies prehistoric origin, but cave paintings can also be of recent production: In the Gabarnmung cave of northern Australia, the oldest paintings certainly predate 28,000 years ago, while the most recent ones were made less than a century ago.
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Historically, letters have existed from the times of ancient India, ancient Egypt and Sumer, through Rome, Greece and China, up to the present day. During the 17th and 18th centuries, letters were used to self-educate. The main purposes of letters were to send information, news and greetings. For some, letters were a way to practice critical reading, self-expressive writing, polemical writing and also exchange ideas with like-minded others.
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The passenger pigeon or wild pigeon (Ectopistes migratorius) is an extinct species of pigeon that was endemic to North America. Its common name is derived from the French word passager, meaning "passing by", due to the migratory habits of the species.
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Scottish inventor Alexander Bain worked on chemical mechanical fax type devices and in 1846 was able to reproduce graphic signs in laboratory experiments. He received British patent 9745 on May 27, 1843 for his "Electric Printing Telegraph".
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Telegraphy is the long-distance transmission of textual messages where the sender uses a semaphore system, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas pigeon post is not. Ancient signalling systems, although sometimes quite extensive and sophisticated as in China, were generally not capable of transmitting arbitrary text messages. Possible messages were fixed and predetermined and such systems.
