24 ENGINEERING ON THE FARM 



meet at the common north point (Fig. 6). An east line is 

 a line which at all points is at right angles to the meridian 

 at that point, or is a line all points of which are the same 

 distance from the north point. 



Methods of determining direction. Various methods of 

 determining direction are in use, as follows: 



Watch method. When the sun is shining, direction can 

 be determined with an ordinary watch. Hold the watch in 

 such a position that the hour hand points to the sun. A line 

 passing over the pivot of the hands halfway between the hour 

 hand and the figure 12 of the dial will point approximately 

 south. 



The North Star. On a clear night the north can be approx- 

 imately determined by the location of the North Star. 

 Everyone should be sufficiently familiar with the stars to 

 identify the North Star readily. 



Short shadows. North can be determined when the sun 

 is shining by means of a rod 20 to 30 inches long erected on a 

 smooth place on the ground or on the top of a table set level. 

 If the top of this rod is tapered to a point, a rather sharp 

 shadow will be thrown. Shortly before twelve o'clock by 

 the sun, the position of the point of the shadow should be 

 marked with a small pin or toothpick. As the shadow con- 

 tinues to shorten, the points should be marked every few 

 minutes. After a time the shadow will begin to lengthen and 

 the markers will increase in distance from the base of the 

 rod. A line from the base of the rod through the shortest 

 marker will be north, and at the time the shortest marker 

 is set it is twelve o'clock by the sun. 



Equal arc. The north point can be determined by the 

 equal-arc method by the same procedure as for short shad- 

 ows. Approximately two or three hours before noon the 

 point of the shadow should be carefully marked. With the 

 distance from the base of the rod to this marker as a radius, 

 describe a circle around the base of the rod. At about the 

 same length of time after twelve o'clock as the marker was 



