72 WOODWARD 



and Orion and the Pleiades," as Carlyle has remarked, ''still 

 shining young and clear in their courses as when the shepherds 

 first noted them on the plains of Shinar"? 



But before astronomy there were mythology and astrology, 

 and we may well marvel how it has been possible, even after 

 the lapse of twenty odd centuries, to educe the orderly precision 

 of science out of the complicated miscellany of fiction, fact, re- 

 Hgion, and poHtics bequeathed to our era by the fertile imagina- 

 tions of our distinguished ancestors. What, for example, could 

 be more confusing than the paleontological jungle called the 

 stellar constellations, with its gods and goddesses ; with its 

 dogs, lions, bears and fish, great and small, northern and 

 southern ; with its horse, whale, and goat ; and with the slimy 

 forms of serpents intertwining them all ? 



Although it is impossible to set any date for the emergence 

 of astronomy out of mythology and astrology, the epoch of 

 Hipparchus undoubtedly is the earliest one of conspicuous ad- 

 vances known to us. This epoch, which may be called also the 

 epoch of the Alexandrian school of science, extends from about 

 300 B.C. to about 150 A.D. It is distinguished by the remark- 

 ably perfect work in pure geometry of Euclid and ApoUonius, 

 and by the still more noteworthy work of Archimedes in laying 

 the foundations of statics and hydrostatics ; it comprises the 

 measurements according to correct principles of the obliquity of 

 the ecliptic and the dimensions of the earth by Eratosthenes ; 

 it includes the observations of the sun, moon, stars and planets 

 collected by Aristyllus and Timocharis and later turned to so 

 good account by Hipparchus ; it embraces the work of Aris- 

 tarchus, who maintained the heliocentric theory of the solar 

 system and who was the first to attempt a measure of the di- 

 mensions of that system by means of the fine fact of observa- 

 tion that the earth, sun and moon form a right triangle with 

 the right angle at the moon when the latter is in dichotomy — 

 or when its face is just half illuminated ; and finally it includes 

 the work of Ptolemy, a worthy disciple of Hipparchus, whose 

 Almagest has come down to our own time. 



From the observational point of view we must rank the prin- 



