4 THE HISTORY OF SCIENCE 



guidance, especially to the pole star and the imperish- 

 able star-group of the northern heavens. The Egyp- 

 tians even developed an apparatus for telling the 

 time by reference to the stars a star-clock similar 

 in its purpose to the sundial. By the Egyptians, 

 also, was carefully observed the season of the year 

 at which certain stars and constellations were visible 

 at dawn. This was of special importance in the case 

 of Sirius, for its heliacal rising, that is, the period 

 when it rose in conjunction with the sun, marked 

 the coming of the Nile flood (so important in the 

 lives of the inhabitants) and the beginning of a 

 new year. Not unnaturally Sirius was an object of 

 worship. One temple is said to have been so con- 

 structed as to face that part of the eastern horizon 

 at which this star arose at the critical season of in- 

 undation. Of another temple we are told that only 

 at sunset at the time of the summer solstice did the 

 sun throw its rays throughout the edifice. The fact 

 that astronomy in Egypt as in Babylonia, where 

 the temples were observatories, was closely associated 

 with religion confirms the view that this science was 

 first cultivated because of its bearing on the practical 

 needs of the people. The priests were the preservers 

 of such. wisdom as had been accumulated in the 

 course of man's immemorial struggle with the forces 

 of nature. 



It is well known that geometry had its origin in 

 the valley of the Nile, that it arose to meet a practi- 

 cal need, and that it was in the first place, as its name 

 implies, a measurement of the earth a crude sur- 

 veying, employed in the restoration of boundaries 

 obliterated by the annual inundations of the river. 



