PRECESSION OF THE EQUINOXES. 93 



The difference, 40 days, converted into degrees, allowing 59' for 

 a day, is 39, very nearly ; dividing this by the annual precession 

 50.2", gives 2796 years since he, flourished, or about 950 years 

 before the Christian era. Meton, the famous astronomer of Athens, 

 says that the star Beta Arietis, was in the vernal equinox in his 

 time, but at the commencement of the present century its longitude 

 was 31, 10', 44", this divided by the annual precession, gives 

 2236 years from the time of Meton's observations to the commence- 

 ment of the 19th century, or 436 years before Christ. If we know 

 the year in which any event occurred, we are frequently enabled 

 to tell nearly the day on which that event transpired. Thus, 

 Thucydides tells us that the investment of Platea, during the fifth 

 year of the Peloponnesian war, which was 426 years before the 

 Christian era, occurred about the time of the heliacal rising of 

 Arcturus. But the heliacal rising of Arcturus then occurred in 

 the month of August, and hence we are enabled to not only give 

 the year, but nearly the month when this event occurred. And 

 we may here remark, that the beginning of the Peloponnesian 

 war, is itself, determined to be 431 years before Christ, by means 

 of an eclipse of the moon which occurred, as can be most accu- 

 rately calculated, April 25th. In the same year, on the 3d of 

 August, an eclipse of the sun was visible at Athens, concerning 

 which, Thucydides, the celebrated Greek historian, remarks : 

 that a solar eclipse happened on a summer's day, on the after- 

 noon, in the first year of the Peloponnesian war, so great that the 

 stars appeared. 



" We are apt to- undervalue the science of the ancients; we 

 ought rather to look upon it with respect and admiration. It is truly 

 astonishing that with their imperfect instruments, they arrived at 

 so much accuracy in their astronomical calculations. The very 

 want of instruments led to an intensity of observation much 

 greater than ours. As the savage inhabitant of the forest with- 

 out a compass, marks his course through the pathless wilds with 

 an accuracy far beyond that of the civilized man, so at a very 

 early period of the world's history, did even barbarous nations 

 learn by the rising and setting of the constellations to regulate the 

 course of the year. However rude therefore, the Romans under 



