INTRODUCTION n 



moreover, did not deny having borrowed from the 

 Chaldeans the idea of the zodiac and the animal con- 

 figurations which divide it into 12 regions. " They, 

 themselves, acknowledged the fishes of the Euphrates 

 in their sign of the Fishes. But, afterwards, they con- 

 nected all these constellations with their national 

 mythology, and thus made unrecognizable the original 

 exotic characters which would have indicated their 

 origin." x However this may be, it was by the use of 

 the zodiacal circle that the Chaldean astronomers 

 were able to predict with more or less exactitude 

 the eclipses of the moon and of the sun. They 

 noticed that the orbit described by the moon is 

 slightly inclined to this circle, and cuts it at two 

 points called nodes, or the head and tail of the 

 dragon, because it is always at these two points that 

 the eclipses of the sun or moon occur. By noting 

 the position of these nodes with regard to the fixed 

 stars, they were able to ascertain that these gradually 

 moved along the zodiacal circle, and returned to their 

 original position at the end of a certain cycle of 

 lunations. 



Having noted the succession of eclipses which were 

 produced during the cycle, it was possible for them to 

 predict their return. It is probable, however, that a 

 calculation of this kind does not belong to a period 

 earlier than the second or third century B.C., and that, 

 before that epoch, the Babylonians were ignorant of 

 the so-called cycle of Saros. 



At first the prediction of the eclipses of the moon 

 could be made by very simple methods, thanks to 

 especially favourable circumstances, which return 



of the Ram at the spring equinox. Now, owing to the pre- 

 cession of the equinoxes, it only arrives there in April. C. 

 Flammarion, Initiation astronomique, Hachette, Paris, 1908, 

 p. 147. 



1 2 Bigourdan, Astronomic, p. 21. 



