A compendium of astronomy; containing the elements of the science, familiarly explained and illustrated, with the latest discoveries. Adapted to the use of schools and academies, and of the general reader (1850)
Olmsted, Denison, 1791-1859 · New York, R. B. Collins · leaf 112
8. First law. The orbits of the earth and all theplanets are ellipses, having the sun in the commonfocus. In a circle all the diameters are equal to each other;but if we take a metallic wire or hoop and draw it out onopposite sides, we elongate it into an ellipse, of which thedifferent diameters… … transverse axis and CD the conjugate of the ellipse AB.By such a process of elongating the circle into an el-lipse, the center of the circle may be conceived of asdrawn opposite ways to E and F, each of which be-comes a focus, and both together are called the foci of theellipse. The distance G£ or…
Astronomy
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