947 



did or did not come true. In one of the reports it says: "The 

 eclipse passes by, it does not take place. If the king asks, what 

 omens have yon seen : the gods (that is the snn and moon) have 

 not been seen with one another; ... at the beginning of the night 

 [the moon rose, . . . therefore] the eclipse passes by, [by day the 

 moon] with the sun will be seen".^) Here, therefore, is given as a 

 reason why an apparently predicted eclipse did not take place, that 

 in the evening the moon rose after sunset, the opposition was 

 therefore passed and had occurred in the day-time. 



The above rule, however, was not always valid. After 6 lunar 

 months (177.18 days) the longitude of the sun, and of the full 

 moon also, has increased in the mean by 174°, 645; during the 

 same time the line of nodes has receded 9°, 383. If the distance, 

 therefore, between the full moon and the nearest node is L — S2=P, 

 the distance of the full moon that follows six months later to the 

 other node is P— 5°,355 + 9°,383 = P + 4°,028. The position of 

 the full moon with regard to the node shifts 4° per six months. 

 F'rom this it follows that for a number of times the lunar eclipse 

 will return regularly after six months; but this series will finally 

 stop, when the distance between full moon and the node has become 

 too great. A partial eclipse is still possible if the distance L — Si is 

 not greater than 10° — 12^°. If at a certain full moon the value of 

 P := L — i2 = — 15°, this quantity for the full moons which come 

 each six months later is: 



—15° — 10°,97 — 6°,94 — 2°,92 +1°,11 +5°,14 +9°,17 4-13°20 

 no eclipse. ? partial, total. total, total ? partial, none. 



Thus 5 or 6 eclipses follow each other regularly ; the series begins 

 with 1 or 2 partial eclipses, then folloio a few total eclipses; these 

 again are folloioed by 1 or 2 partial eclipses, and then the series 

 is finished. 



In such a favourable climate as that of Babylon, where, with the 

 exception of a few winter months, every phenomenon in the heavens 

 could be regularl}' observed every night, the priest-astrologers must 

 have gradually noticed this regularity. If they observed a partial 

 eclipse which had had no i)redecessor 6 or 12 months before, they 

 knew that a fresh series had begun, and they could predict a number 

 of coming eclipses with certainty. 



ScHiAPARELLi has pointed out this simple method of prediction by 



1) Thompson, The reports of the magicians and astrologers, N". 275A ; Kugler, 

 Sternkunde etc. II, p. 64. 



