
1) Animation technique 2) Optical illusion
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https://www.crosswordclues.com/clue/thaumatrope

A thaumatrope is a toy that was popular in the 19th century. A disk with a picture on each side is attached to two pieces of string. When the strings are twirled quickly between the fingers the two pictures appear to blend into one due to the persistence of vision. Examples of common thaumatrope pictures include a bare tree on one side of the disk...
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http://en.wikipedia.org/wiki/Thaumatrope

gadged showing persistence of visual impressions using spinning disk
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http://phrontistery.info/t.html

• (n.) An optical instrument or toy for showing the presistence of an impression upon the eyes after the luminous object is withdrawn.
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http://thinkexist.com/dictionary/meaning/thaumatrope/

<optics> An optical instrument or toy for showing the presistence of an impression upon the eyes after the luminous object is withdrawn. ... It consists of a card having on its opposite faces figures of two different objects, or halves of the same object, as a bird and a cage, which, when the card is whirled rapidlz round a diameter by the st...
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http://www.encyclo.co.uk/local/20973

1 Optical toy, developed in the late 1820s, consisting of a card or disc with two different figures drawn on each side. When it is rotated the two figures appear to combine into one. 2 Cylinder bearing a series of figures on the inside and a series of slits on the outside. The figures are viewed through the slits and when the cylinder is rotated ap …...
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http://www.encyclo.co.uk/visitor-contributions.php
Thau'ma·trope noun [ Greek ... a wonder + ... to turn.]
(Opt.) An optical instrument or toy for showing the presistence of an impression upon the eyes after the luminous object is withdrawn. » It consists of a card having on its opposite faces figures of two different objects, or halves of t...
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http://www.encyclo.co.uk/webster/T/38

A thaumatrope is a card or disc with two different figures drawn one each side. These images apparently merge when the card or disk is rotated rapidly. Thaumatropes are used to demonstrate the persistence of visual impressions.
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http://www.probertencyclopaedia.com/browse/AT.HTM

thaumatrope 1. A 'magic card' with different pictures on either side so that when the card is rapidly twirled, the images appear to combine as one. 2. Applied to a disk or cylinder bearing a series of figures which, on being rapidly rotated and viewed through a slit, produce the impression of a moving object. An example is a horse on one side and a...
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http://www.wordinfo.info/words/index/info/view_unit/2131/
No exact match found.