Analog Computers, Automatons
A short list of other precursors to the mechanical calculator must include the Greek Antikythera mechanism from around 100 BC, an out of place, unique, geared mechanism followed more than a millennium later by early mechanical clocks and geared astrolabes ; These machines were all made of toothed gears linked by some sort of carry mechanisms. They belong to a group of mechanical analog computers which, once set, are only modified by the continuous and repeated action of their actuators (crank handle, weight, wheel...)
Some measuring instruments and automatons were also precursors to the calculating machine.
An odometer, instrument for measuring distances, was first described around 25 BC by the roman engineer Vitruvius in the tenth volume of his De architectura. It was made of a set of toothed gears linked by a carry mechanism ; the first one was driven by one of the chariot wheels and the last one dropped a small pebble in a bag for each Roman mile traveled.
A Chinese text of the third century AD described a chariot equipped with a geared mechanism that operated two wooden figures. One would strike a drum for every Chinese Li traveled, the other one would strike a gong for every ten Li traveled.
Around the end of the tenth century, the French monk Gerbert d'Aurillac, whose abacus taught the Hindu-Arabic numeral system to the Europeans, brought back from Spain the drawings of a brazen head, invented by the Moors, which answered Yes or No to the questions it was asked (binary arithmetic).
Again in the thirteenth century, the monks Albertus Magnus and Roger Bacon built mechanical speaking heads made of earthware without any further development (Albertus Magnus complained that he had wasted forty years of his life when Thomas Aquinas, terrified by this speaking machine, destroyed it).
The Italian polymath Leonardo da Vinci drew an odometer before 1519.
In 1525, the French craftsman Jean Fernel built the first pedometer. It was made in the shape of a watch and had 4 dials (units, tens, hundreds, thousands) linked by a single tooth carry mechanism.
In 1623 and 1624, Wilhelm Schickard drew a calculating clock on two letters that he sent to Kepler. Schickard's machine was the first of five unsuccessful attempts of designing a direct entry calculating clock in the 17th century (including the designs of Tito Burattini, Samuel Morland and René Grillet). The first calculating clock worthy of its name was built by the Italian Giovanni Poleni in the 18th century (1709) and it was a two-motion calculating clock were the numbers are inscribed first and then are processed (see Pascal versus Schickard).
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