THE CONQUEST OF TIME AND SPACE 



degree of accuracy without the use of the sextant or of 

 any astronomical equivalent more elaborate than, let 

 us say, an ordinary lead pencil. It is only necessary to 

 push the point of the pencil into a level surface of ice 

 or snow and leave it standing there in a vertical posi- 

 tion. If, then, the shadow cast by the pencil is noted 

 from time to time, it will be observed that its length is 

 always the same; that, in other words, the end of the 

 shadow as it moves slowly about with the sun describes 

 a circle in the course of twenty-four hours. If the at- 

 mospheric conditions had remained uniform, so that 

 there was no variation in the amount of refraction to 

 which the sun's rays were subjected, the circle thus 

 described would be almost perfect, and would in itself 

 afiFord a demonstration that would appeal to the least 

 scientific of observers. 



An even more simple demonstration might be made 

 by having an Eskimo stand in a particular spot and 

 marking the length of his shadow as cast on a level 

 stretch of ice or snow. Just twelve hours later let the 

 Eskimo stand at the point where a mark had been 

 made to indicate the end of the shadow, and it would 

 be found that his present shadow — cast now, of course, 

 in the opposite direction — would reach exactly to the 

 point where he had previously stood. The only diffi- 

 culty about this simple experiment would result from 

 the fact that the sun is never very high as viewed from 

 the pole and therefore the shadow would necessarily be 

 long. It might therefore be difficult to find a level area 

 of sufficient extent on the rough polar sea. In that 

 case another measurement similar in principle could be 



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