I.] THE THAMES. 7 



appears to rise slowly in the sky, and mounts to its greatest 

 height at noon. At the instant of reaching its greatest 

 height, or in other words at exact noon, the sun is pre- 

 cisely in the south. If, then, you place yourself in such 

 a position as to have the sun shining full in your face 

 at that particular time, you must be facing south ; and 

 you will consequently have your back to the north, your 

 right hand towards the west, and your left towards the 

 east. 



As true noon does not always coincide with 12 o'clock, 

 as indicated by an ordinary timekeeper, it is necessary to 

 explain how it may be determined. Thrust a stick verti- 

 cally into the ground, and observe, at different hours of the 

 day, the length and direction of its shadow cast by the sun. 

 When the sun is rising in the sky, the shadow is thrown 

 towards the west ; and when the sun is going down, it is 

 thrown towards the east; at noon, however, it inclines 

 neither to the east nor to the west, but falls exactly in a 

 north-and-south line ; and, moreover, the shadow is then 

 shorter than at any other time. If, therefore, you observe 

 when the shadow is shortest, that time will be exact noon. 

 The line indicated by the shadow at noon is known as the 

 meridian line or mid-day line. That end of the shadow-line 

 which is towards the sun points to the south, and the oppo- 

 site end to the north. If then a line be drawn anywhere 

 at right angles across the shadov/, the right-hand end of the 

 cross-line, as you look to the south, points towards the 

 west, and the left hand towards the east. 



It is not easy, however, by merely looking at the shadow, 

 to say when it is exactly reduced to its shortest length. It 

 is well, therefore, to observe the shadow at some time in 

 the forenoon and mark its length — say by sticking a peg in 

 the ground, and then, in the afternoon, to observe the 



