74 INTRODUCTION TO GENERAL SCIENCE 



c. Turn the globe so that the north end of the axis points 

 away from the source of light and answer the same questions 

 as in (6). 



d. What season is represented by (a), (6), and (c), respec- 

 tively? Does the length of day vary at the equator? 



53. THE CALENDAR 



Upon the rotation and revolution of the earth is based our 

 calendar, or record of time. There have been a great many 

 changes in the calendar since man first tried to reckon time. 

 Much has been discovered concerning the exact time of the 

 rotation of the earth, and its revolution around the sun, and 

 the calendar has been altered to meet known conditions. 

 Time has been reckoned by the moon, but more generally by 

 the seasons, and by day and night. The Julian Calendar, 

 prepared by learned men at the direction of Julius Caesar, 

 was in force until 1582, when it was found to be ten days be- 

 hind time. Pope Gregory caused this time to be dropped 

 and the calendar brought up to date, and ordered that every 

 fourth year should have an extra day. This was called the 

 Gregorian Calendar. This calendar is not exactly correct, 

 but by the method of omitting the leap year at the end of each 

 century, except those centuries that are divisible by four hun- 

 dred, the calendar will be nearly correct. 



References : 



1. 1002 : 240-241. The Calendar. 



2. 1304 : 7-8. Effects of Revolution and Rotation, 

 a. 1001 : 85-87. The Calendar. 



6. 1003 : 133-136. The Calendar. 



c. 1004 : 101-104. The Year and the Calendar 



d. 1303 : 7-8. Day and Night : a Natural Unit of Time. 



e. 1309 : 28-29. The Calendar and Time. 

 /. 1312 : 29-32. The Calendar and Time. 



