HOW A WATCH MAY BE USED AS A COMPASS 



EVERAL years ago a correspondent of " Truth " 

 (London) gave the following simple directions for 

 finding the points of the compass by means of 

 the ordinary pocket watch : " Point the hour hand 

 to the sun, and south is exactly half way between the hour 

 hand and twelve on the watch, counting forward up to 

 noon, but backward after the sun has passed the meridian." 

 Professor Ball, in his "Mathematical Recreations and 

 Problems," gives more complete directions and explanations. 

 He says : 



" The position of the sun relative to the points of the 

 compass determines the solar time. Conversely, if we 

 take the time given by a watch as being the solar time 

 (and it will differ from it only by a few minutes at the 

 most), and we observe the position of the sun, we can find 

 the points of the compass. To do this it is sufficient to 

 point the hour-hand to the sun and then the direction which 

 bisects the angle between the hour and the figure XII will 

 point due south. For instance, if it is four o'clock in the 

 afternoon, it is sufficient to point the hour-hand (which 

 is then at the figure IIII) to the sun, and the figure II on 

 the watch will indicate the direction of south. Again, if 

 it is eight o'clock in the morning, we must point the hour- 

 hand (which is then at the figure VIII) to the sun, and the 

 figure X on the watch gives the south point of the compass. 



" Between the hours of six in the morning and six in 

 the evening the angle between the hour and XII, which 

 must be bisected is less than 180 degrees, but at other times 

 the angle to be bisected is greater than 180 degrees ; or per- 

 haps it is simpler to say that at other times the rule gives 

 the north point and not the south point. 



"The reason is as follows: At noon the sun is due 



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