140 NOMOS. 



and counter-wave which continually follow the sun 

 and moon, how is it that these waves do not break 

 with much greater force upon the eastern 

 shores of the sea than upon the western ? 



prTse'nt'the- ^ W * S ** ^at ^ e ^6 S6tS 6( l Ua % U P n 



oryofthe the coasts, and this equally in all direc- 



tides* 



tions ? 



Nor is the difficulty diminished when we endea- 

 vour to realise the action of the sun and moon upon 

 the tides at an island in mid-ocean, where the local 

 impediments to the free flow of the tidal wave are 

 as few as possible. If we do this the result is most 



startling. In the following diagrams we 



A third great . P 



objection to have represented the position ot the sun 



and moon with respect to the tides of the 

 island of St. Helena, in the month of 

 February, 1853. In these diagrams E is the earth, 

 s the sun, and M the moon. The spot upon the sur- 

 face of E indicates the position of St. Helena ; and 

 the intersecting lines a b and a' b' } that of the two 

 daily tides. The position of St. Helena and of the 

 tides changes as the earth, E, revolves upon her 

 axis ; the position of the moon, M, also changes as 

 she moves in her orbit ; but the position of the sun, 

 S, is stationary. It is always noon at the part of the 

 earth which is immediately under the sun ; and hence 

 we may estimate the time of any particular tide by 

 the distance on either side from this point. As to 

 the rest, we must suppose that the earth, E, rotates 

 in the direction of the arrow placed upon it ; and 

 that the moon, M, revolves in the direction indicated 

 by the accompanying arrow. We give a diagram 



