78 PLINY' S NATCTBAL HISTOET. [Book XVIII. 



appearance is rather an " occultation " than a " setting." — 

 Considered, again, in another point of view, when upon cer- 

 tain da)^8 they begin to appear or disappear, at the setting: 

 or the rising of the sun, as the case may be, these are called 

 their morning or their evening settings or risings, according 

 as each of these phsenomena takes place at day-break or twilight. 

 It requires an interval of three quarters of an hour at least be- 

 fore the rising of the sun or after his setting, for the stars to 

 be visible to us. In addition to this, there are certain stars 

 which rise and set twice.^ All that we here state bears refer- 

 ence, it must be remembered, to the fixed stars only. 



CHAP. 59. THE EPOCHS OF THE SEASONS. 



The year is divided into four periods or seasons, the recurrence 

 of which is indicated by the increase or diminution of the 

 daylight. Immediately after the winter solstice the days begin 

 to increase, and by the time of the vernal equinox, or in other 

 words, in ninety days and three hours, the day is equal in 

 length to the night. After this, for ninety-four days and 

 twelve hours, the days continue to increase, and the nights to 

 diminish in proportion, up to the summer solstice ; and from 

 that point the days, though gradually decreasing, are still in 

 excess of the nights for ninety-two days, twelve hours, until the 

 autumnal equinox. At this period the days are of equal 

 length with the nights, and after it they continue to decrease 

 inversely to the nights until the winter solstice, a period 

 of eighty-eight days and three hours. In all these calcu- 

 lations, it must be remembered, equinoctial-^ hours are spoken 

 of, and not those measured arbitrarily in reference to the 

 length of any one day in particular. All these seasons, too, 

 commence at the eighth degree of the signs of the Zodiac. 

 The winter solstice begins at the eighth degree of Capricorn, 

 the eighth-^ day before tlie calends of January, in general f'^ the 

 vernal equinox at the eighth degree of Aries; the summer 

 solstice, at the eighth degree of Cancer ; and the autumnal 

 equinox at the eighth degree of Libra : and it is rarely that 



*'' See c. 69, as to Arctiirus and Aquila. 



2^ He speaks of Equinoctial hours, these being in all cases of the same 

 length, in contradistinction to the Temporal, oV Unequal hours, which 

 with the Romans were a twelfth part of the Natural day, from sunrise to 

 sunset, and of course were continually varying. 



-'•' Twenty-fifth of December. so pgrc. 



