Cliap. 10.] ACCOtJlfT OF THE -WOELD. 39 wMe an eclipse of the moon takes place only when she is at the full, and is always a little farther advanced than the preceding eclipsed Now there are eclipses of both these stars in every year, which take place below the^ earth, at stated days and hours ; and when they are above it^ they are not always ^dsible, sometimes on account of the clouds, but more frequently, from the globe of the earth being opposed to the vault of the heavens^ It was discovered two hundred years ago, by the sagacity of Hipparchus, that the moon is sometimes eclipsed after an interval of five months, and the sun after an interval of seven^ ; also, that he becomes invi- sible, wliile above the horizon, t^dce in every thirty days, but that this is seen in different places at different times. But the most wonderful circumstance is, that while it is ad- mitted that the moon is darkened by the shadow of the earth, this occurs at one time on its western, and at another time on its eastern side. And farther, that although, after the rising of the sun, that darkening shadow ought to be below the earth, yet it has once happened, that the moon has been eclipsed in the west, while both the luminaries have been above the horizon^ And as to their both being invisible in the space of fifteen days, this very thing happened while the Vespasians were emperors, the father being consul for the third time, and the son for the second^ 1 " Hoc enim periodo (223 mensium) plerumque redeunt eclipses, non multiun differentes, denis tamen gradibus zodiaci antecedentes ;" Kepler, as quoted by Alexandi-e, in Lemaire, ii. 238. 2 The terms " sub terra" and " supeme" are interpreted, by most ot the commentators, below and above the horizon respectively ; see Marcus m Aiasson, ii. 307. „ _ 3 " globo ten-ffi obstante convexitatibus mundi." The term convexus, as apphed to the heavens, or visible firmament, simply signifies arched j not opposed to cotwave, hke the Enghsh word convex. 4 This pomt is discussed by Ptolemy, Magn. Const, vi. 6 ; " De distantia eehpticorum mensium." See also the remarks of Hardoum m Lemau-e, ii. 260, 261 ; and of Poinsmet, i. 67. i a *• 6 These arc styled horizontal eclipses ; they depend on the rch-active power of the atmosphere, causing the sun to be visible above the horizon, althouf^h it is actuaUy below it. Protier states, that echpses of tlus de- scription occurred on the 17th July, 1590, on the 30tb November, 16-18, and on the 16th January, 1660 ; Lemaire, ii. 260. ^ , 6 This is supposed to have been in the year 72 of oiu- rora, when it is said that the sun was echpsed, in Italy, on the 8th, and the moon on the 22nd of February j see Hardouin and Alexandre, in Lemaire, ii. 261,
