Eclipses 



cision was still less; the case of the eclipse of 

 1684 may be cited, because although it had 

 been announced to be total at Rome only three- 

 quarters of the sun were actually hidden. 



But ages before Kepler and Newton ex- 

 perience had enabled approximate rules to be 

 framed. Thus it is related that Sulpicius Gallas, 

 a lieutenant of .ZEmilius Paulus, succeeded in 

 preventing a mutiny of his army by predicting 

 an eclipse of the moon. These astronomical 

 notions seem to owe their origin to the Eastern 

 races; the Chaldeans had noticed that eclipses 

 recur at regular intervals. This Chaldean period, 

 called also Saros, of eighteen years eleven days' 

 duration, does, as a fact, restore the sun, the 

 earth and the moon to the same relative positions. 

 It contains seventy-five eclipses forty-six of 

 the sun z and twenty-nine of the moon. 



1 Not forty-one, as the most recent writers state owing to 

 a mistake, whose cause is sufficiently original to be men- 

 tioned. Halley, having made a table of the eclipses belonging 

 to a Chaldean period, printed them on two consecutive pages 

 of his Treatise of Astronomy ; but as he could only find room 

 on the first page for forty-one solar eclipses, and on the second 

 page for the twenty-nine lunar eclipses, he relegated the five 

 remaining solar eclipses to a note, which must have escaped the 

 attention of the first author who borrowed these figures, and 

 all subsequent books have reproduced this singular error. 



195 



