Herschel, John F. W. (John Frederick William), Sir, 1792-1871 · London : Longman, Brown, Green, Longmans, and Roberts · leaf 495
give rise to inequalities of very long periods, of which more presently.* (670.) The variation of the length of the axis of the disturbed orbit is due solely to the action of the tangential disturbing force. It is otherwise with that of its excentricity and of the position of its axis, or, which is… … and, commencing, as the simplest case, with that of the tan¬ gential force ; — let P be the place of the disturbed planet in its elliptic orbit APB, whose axis at the moment is A S B and focus S. Suppose Y P Z to be a tangent to this orbit at * 41 revolutions of Neptune are nearly equal to 81 of…
Astronomy
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![An illustration from Nicolai Copernici Torinensis De reuolutionibus orbium coelestium, libri VI : Habes in hoc opere iam recens nato, & aedito, studiose lector, motus stellarum, tam fixarum, quàm erraticarum, cum ex ueteribus, tum etiam ex recentibus obseruationibus restitutos: & nouis insuper ac admirabilibus hypothesibus ornatos. Habes etiam tabulas expeditissimas, ex quibus eosdem ad quoduis tempus quàm facillime caculare poteris. Igitur eme, lege, fruere. [Line in Greek] (1543)](https://img.insideoutlibrary.com/img/200/ia-nicolaicopernici00cope-359-250.webp)
