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n. An apparatus that shows how the movement of the earth on its axis and around the sun causes day and night and the seasons.

n. An instrument used to show how the rotation of the Earth on its axis and its orbit around the Sun cause day and night and the seasons.

n. an apparatus for exhibiting the mathematical relations of the earth, in which the principles of orthogonal projection are applied.

n. An instrument for showing in what manner the causes operate which produce the succession of day and night and the changes of the seasons: a kind of orrery.

"A tellurion will not teach the changes of the seasons; bundles of splints, notation; nor black-board examples, the law of agreement; unless these are brought under the child's mental apprehension."

orthogonal tellurion    tellurium