82 



THE BOOK OF NATURE STUDY 



if a small, difference in the time of noon. But round London, 

 for instance, people sometimes travel twenty miles every morning 

 into business, and it would be obviously impossible for them 

 to catch their trains and carry on their business if there was 

 a different time every few miles. Therefore they agreed that 

 the time of one particular place should be taken over a wide area, 

 generally over one country. Thus many countries, unless they 

 are very large, take their time from their capital, Great Britain 

 from London, Ireland from Dublin, France from Paris, and so on, 

 this being done simply as a matter of convenience. One should 

 go on to point out that the change of time at the frontier of a 

 country often makes great inconvenience, as when a traveller 

 goes to Chamonix from Paris through Geneva. Here he finds 

 that when he gets to Geneva he loses an hour, but as he travels 

 on towards Chamonix, which is in French territory, he regains 

 that hour. As he is journeying eastward all the time, this 

 example is well adapted to show the artificiality of standards 

 of time. 



Shadow experiments may also be used to give some idea of 

 the meaning of the earth's revolution, though the term itself 



should not be mentioned. If 

 in the previously described 

 shadow experiments a stick 

 has been used, a slender lath 

 should now be taken, and so 

 placed that one extremity 

 rests on the top of the stick 

 and the other end on the 

 ground (see Fig. 5). In an 

 indoor experiment with a 

 stout pin, a piece of card- 



FlG. 5 .-The altitude of the sun at London at the board be used j n 



equinoxes, experimentally shown. J 



same way. In either case the 



lath or card should be adjusted so that the end touching the ground 

 reaches to the extremity of the noon-tide shadow in one of the 

 observations already made. If the present observation be made at 

 noon, make the class notice that when the lath is arranged in this 

 way it points in the direction of the sun, and in consequence the 



