$$ -tO The Beginnings of Astronomy 3 



approaches the time of sunrise, until the moon becomes 

 altogether invisible. After two or three nights the new 

 moon reappears, and the whole series of changes is repeated. 

 The different forms thus assumed by the moon are now 

 known as her phases ; the time occupied by this series of 

 changes, the month, would naturally suggest itself as a con- 

 venient measure of time ; and the day, month, and year 

 would thus form the basis of a rough system of time- 

 measurement. 



5. From a few observations of the stars it could also 

 clearly be seen that they too, like the sun and moon, 

 changed their positions in the sky, those towards the east 

 being seen to rise, and those towards the west to sink and 

 finally set, while others moved across the sky from east to 

 west, and those in a certain northern part of the sky, though 

 also in motion, were never seen either to rise or set. Although 

 anything like a complete classification of the stars belongs 

 to a more advanced stage of the subject, a few star groups 

 could easily be recognised, and their position in the sky 

 could be used as a rough means of measuring time at night, 

 just as the position of the sun to indicate the time of day. 



6. To these rudimentary notions important additions 

 were made when rather more careful and prolonged obser- 

 vations became possible, and some little thought was 

 devoted to their interpretation. 



Several peoples who reached a high stage of civilisation 

 at an early period claim to have made important progress 

 in astronomy. Greek traditions assign considerable astro- 

 nomical knowledge to Egyptian priests who lived some 

 thousands of years B.C., and some of the peculiarities of 

 the pyramids which were built at some such period are at 

 any rate plausibly interpreted as evidence of pretty accurate 

 astronomical observations ; Chinese records describe observa- 

 tions supposed to have been made in the 25th century B.C.; 

 some of the Indian sacred books refer to astronomical 

 knowledge acquired several centuries before this time ; and 

 the first observations of the Chaldaean priests 'of Babylon 

 have been attributed to times not much later. 



On the other hand, the earliest recorded astronomical 

 observation the authenticity of which may be accepted 

 without scruple belongs only to the 8th century B.C. 



