CLAUDIUS PTOLEMY:

TETRABIBLOS

OR THE QUADRIPARTITE MATHEMATICAL TREATISE

6. Of the Time of the Predicted Events.

The second and chronological heading, whereby we should learn the times of the events signified and the length of their duration, we shall consider as follows. inasmuch as the eclipses which take place at the same time are not completed in the same number of ordinary hours in every locality, and since the same solar eclipses do not everywhere have the same degree of obscuration or the same time of duration, we shall first set down for the hour of the eclipse, in each of the related localities, and for the altitude of the pole, centres, as in a nativity; secondly, how many equinoctial hours the obscuration of the eclipse lasts in each. For when these data are examined, if it is a solar eclipse, we shall understand that the predicted event lasts as many years as the equinoctial hours which we discover, and if a lunar eclipse, as many months. The nature of the beginnings and of the more important intensifications of the events, however, are deduced from the position of the place of the eclipse relative to the centres. For if the place of the eclipse falls on the eastern horizon, this signifies that the beginning of the predicted event is in the first period of four months from the time of the eclipse and that its important intensifications lie in the first third of the entire period of its duration; if on the mid-heaven, in the second four months and the middle third; if upon the western horizon, in the third four months and the final third. The beginnings of the particular abatements and intensifications of the event we deduce from the conjunctions which take place in the meantime, if they occur in the significant regions or the regions in same aspect to them, and also from the other movements of the planets, if those that effect the predicted event era either rising or setting or stationary or at evening rising, and are at the same time in same aspect to the zodiacal signs that hold the cause; for planets when they are rising or stationary produce intensifications in the events, but when setting, and under the rays of the sun, or advancing at evening, they bring about an abatement.




Ptolemy's Tetrabiblos

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