List, C, Hall, T. G. (Thomas Grainger), 1803-1881 · Philadelphia : Thomas Cowperthwait & Co. and Carey & Hart · leaf 52
rationalhorizon coincides with the equator. For the purpose of illustration, circles, insteadof spheres, have been used in the figure explana-tory of the four positions of the earth; for, by thecircles, the angle made by a line drawn from thesun to the centre of the earths axis, on which… … easily presented to the eye, by means of fourcircular pieces of pasteboard, about an inch indiameter, and attached to a string arranged in acircular form, taking care that the line ns isalways parallel to itself. The above figure will exhibit the four positionsof the earth considered as a sphere.…
Astronomy
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