OF THE MOTIONS OF THE PLANETS AND THE GENERAL LAWS OF THEIR ASPECTS

Latine · Mayhoff 1906

Errantium autem tres, quas supra solem diximus sitas, occultantur meantes cum eo, exoriuntur vero matutino discedentes partibus numquam amplius undenis. postea radiorum eius contact reguntur et in triquetro a partibus CXX stationes matutinas faciunt, quae et primae vocantur, mox in adverso a partibus CLXXX exortus vespertinos, iterumque in CXX ab alio latere appropin- quantes stationes vespertinas, quas et secundas vocant, donec assecutus in partibus duodenis occultet illas, qui vespertini occasus appellantur. Martis stella, ut propior, etiam ex quadrato sentit radios, a XC partibus, unde et nomen accepit motus primus et secundus nonagenarius dictus ab utroque exortu. eadem stationalis senis mensibus commoratur in signis, alioqui bimenstris, cum ceterae utraque statione quaternos menses non inpleant. inferiores autem duae occultantur in coitu vespertino simili modo, relictaeque a sole totidem in partibus faciunt exortus matutinos, ad quos longissimis distantiae suae metis solem insequuntur adeptaeque occasu matutino conduntur ac praetereunt. mox eodem intervallo vespere exoriuntur usque ad quos diximus terminos. ab his retrogradiuntur ad solem et occasu vespertino delitescunt. Veneris stella et stationes duas, matutinam vespertinamque, ab utroque exortu facit a longissimis distantiae suae finibus, Mercurii stationum breviore momento quam ut deprehendi possint.

Haec est luminum occultationumque ratio,per- plexior motu multisque involuta miraculis, siquidem magnitudines suas et colores mutant, et eaedem ad septentrionem accedunt abeuntque ad austrum terrisque propiores aut caelo repente cernuntur. in quibus aliter multa quam priores tradituri fatemur ea quoque illorum esse muneris qui primi vias quaerendi demonstraverint, modo ne quis desperet saecula proficere semper. pluribus de causis haec omnia accidunt: prima circulorum, quos Graeci ἀψῖδας in stellis vocant; etenim Graecis utendum erit vocabulis. sunt autem hi sui cuique earum aliique quam mundo, quoniam terra a verticibus duobus, quos appellaverunt polos, centrum caeli nec non et signiferi est oblique inter eos siti. omnia autem haec constant ratione circini semper indubitata. ergo ab alio cuique centro apsides suae exsurgunt ideoque diversos habent orbes motusque dissimiles, quoniam interiores apsidas necesse est breviores esse.

English · Bostock & Riley 1855–57

The three planets, which, as we have said, are situated above the sun, are visible when they come into conjunction with him. They rise visibly in the morning, when they are not more than 11 degrees from the sun; they are afterwards directed by the contact of his rays, and when they attain the trine aspect, at the distance of 120 degrees, they take their morning stationary positions, which are termed primary; afterwards, when they are in opposition to the sun, they rise at the distance of 180 degrees from him. And again advancing on the other side to the 120th degree, they attain their evening stations, which are termed secondary, until the sun having arrived within 12 degrees of them, what is called their evening setting becomes no longer visible. Mars, as being nearer to the sun, feels the influence of his rays in the quadrature, at the distance of 90 degrees, whence that motion receives its name, being termed, from the two risings, respectively the first and the second nonagenarian. This planet passes from one station to another in six months, or is two months in each sign; the two other planets do not spend more than four months in passing from station to station.

The two inferior planets are, in like manner, concealed in their evening conjunction, and, when they have left the sun, they rise in the morning the same number of degrees distant from him. After having arrived at their point of greatest elongation, they then follow the sun, and having overtaken him at their morning setting, they become invisible and pass beyond him. They then rise in the evening, at the distances which were mentioned above. After this they return back to the sun and are concealed in their evening setting. The star Venus becomes stationary when at its two points of greatest elongation, that of the morning and of the evening, according to their respective risings. The stationary points of Mercury are so very brief, that they cannot be correctly observed.

The above is an account of the aspects and the occultations of the planets, a subject which is rendered very complicated by their motions, and is involved in much that is wonderful; especially, when we observe that they change their size and colour, and that the same stars at one time approach the north, and then go to the south, and are now seen near the earth, and then suddenly approach the heavens. If on this subject I deliver opinions different from my predecessors, I acknowledge that I am indebted for them to those individuals who first pointed out to us the proper mode of inquiry; let no one then ever despair of benefiting future ages.

But these things depend upon many different causes. The first cause is the nature of the circles described by the stars, which the Greeks term apsides, for we are obliged to use Greek terms. Now each of the planets has its own circle, and this a different one from that of the world; because the earth is placed in the centre of the heavens, with respect to the two extremities, which are called the poles, and also in that of the zodiac, which is situated obliquely between them. And all these things are made evident by the infallible results which we obtain by the use of the compasses. Hence the apsides of the planets have each of them different centres, and consequently they have different orbits and motions, since it necessarily follows, that the interior apsides are the shortest.