12 HISTORY OF SCIENCE. 



science by the several individuals of the Ionian school, or how much 

 of their science was derived from foreign sources. The adjustment 

 of the calendar was a subject which received much attention from the 

 Greek astronomers. The necessity of some 'arrangement by which 

 the divisions of the year used in the civil reckoning of time should 

 always correspond with the same seasons, will be obvious to every 

 reader. The difficulty of making this adjustment is occasioned by 

 the fact that the real year corresponds with no exact number of days, 

 nor does the month, i.e., the time required for the moon's revolution, 

 form any aliquot part of the year. Suppose, then, that the year and 

 the first month commence together at a given instant, the beginning 

 of the next year cannot possibly coincide with the beginning of a lunar 

 period. The Greek astronomers at length succeeded in finding a 

 practically useful solution of the problem of arranging the calendar. 

 It was discovered that two hundred and thirty-five lunar revolutions 

 occupied almost exactly the time of nineteen solar years. Conse- 

 quently every nineteen years the beginning of the year would coincide 

 with the beginning of a month, and therefore the calendar could be 

 arranged simply and conveniently for a cycle of nineteen years. This 

 was known as the Cycle of Meton, and its first epoch, when it was 

 definitely adopted by all the Grecian States, corresponds with the 

 year B.C. 432. On this cycle our ordinary calendar is still based, as 

 may easily be seen by any one who will refer to the tables usually 

 prefixed to the Book of Common Prayer of the Church of England. 

 He will there observe that in order to determine the dates of certain 

 festivals which depend upon the lunar periods, it is necessary to as- 

 certain the Golden Number for the year in question, the golden number 

 being simply the ordinal position of the year in the Metonic cycle of 

 nineteen years. 



We pass on now to a philosopher of another school. His was a 

 name greatly renowned in the ancient world, for he was the founder 

 of the famous sect of the Pythagoreans. 



PYTHAGORAS (B.C. 570 500) was born in Samos, an island belonging 

 to the lonians, and he appears to have visited every land where any 

 information on things human or divine was to be obtained. In Egypt, 

 where he lived for many years, he gained the confidence of the priests 

 and acquired a knowledge of their geometry. The Chaldeans made 

 him acquainted with their astronomy, the Phoenicians taught him 

 arithmetic, and to the Indians he was perhaps indebted for his the- 

 ology. After many years of absence he returned to Samos, only again 

 to quit it for political reasons and settle at Cretona, a city founded by 

 the Greeks in the most southern part of Italy. It was here that 

 Pythagoras established the school of philosophy which was afterwards 

 called the Pythagorean or Italian. 



The scientific contemplation 'of nature appears to have interested 

 Pythagoras chiefly as a basis for his moral and religious views. He 



