Chap. 10.] ACCOUNT OP THE WOELD. 80 



while an eclipse of the moon takes place only when she is 

 at the full, and is always a little farther advanced than the 

 preceding eclipse \ ]^«fow 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 ai*e 

 not always visible, 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 ai'ter an interval of five months, and the 

 sun after an interval of seven* ; also, that he becomes invi- 

 sible, wliile above the horizon, twice 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*. 



* " Hoc enim periodo (223 mensium) pleruinque redeunt eclipses, non 

 multum differentes, denis tamen gradibus zodiaci antecedentes j Kepler, 

 as quoted by Alexandre, in Lemaire, ii. 238. 



2 The terms " sub terra" and " supeme" are interpreted, by most of the 

 commentators, below and above the horizon respectively ; see Marcus in 

 Ajasson, ii. 307. 



3 •' globo terrse obstante convexitatibus mundi." The term convexus, 

 as applied to the heavens, or visible firmament, simply signifies arched j 

 not opposed to concave, like the English word convex. 



* This point is discussed by Ptolemy, Magn. C!onst. vi. 6 ; *'De distantia 

 echpticorum mensium." See also the remarks of Hardouin in Lemaire, 

 ii. 260, 261 ; and of Poinsinet, i. 67. 



* These are styled horizontal echpses ; they depend on the refractive 

 power of the atmosphere, causing tlie sun to be visible above the horizon, 

 although it is actually below it. Brotier states, that echpses of this de- 

 scription occurred on the 17th July, 1590, on the 30th November, 1648, 

 and on the 16th January, 1660 ; Lemaire, ii. 260. 



^ This is supposed to have been in the year 72 of our aera, 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« 



