170 Baron N. Schilling on the Constant Currents 



Before we compare, however, with one another the quantities 

 of these two forces, it will be necessary to illustrate further what 

 has been said, representing the earth in the plane of the meridian. 



Let the circle P A SE (fig. 5) be a terrestrial meridian, and 



Fig. 5. 



L the centre of the moon (or of the sun), which, as before, is on 

 the equator. The dotted line p as e marks the form of the tidal 

 ellipsoid. Through the rotation of the earth the moon appa- 

 rently moves from east to west ; with it the ellipsoid p a s e turns 

 about the axis P S, and develops, as we have seen, at the equator 

 two forces opposed one to the other. The one, the force effect- 

 ing the flood-current, directs its course from east to west, and 

 in the case here given is strongest at the equator, on which the 

 cusps of the ellipsoid move forward as long as the moon is on 

 the equator. This force will act in nearly the same direction on 

 both sides of the equator ; only it must rapidly diminish as the 

 latitude increases ; and in the latitude of the points m, where 

 there is no rise of the water, the force acting from east to west 

 must be =0. Further polewards the tendency to form the 

 tidal ellipsoid may probably develop an inconsiderable current 

 from the pole towards the equator, as shown by the lines p L 

 and s L. 



The ebb-current force acts from west to east, as if the circle 

 pCsD revolved in this direction on the axis P S. As already 

 said, it arises from the circumstance that all points in one half 

 of the earth are brought nearer to the moon by the rotation, 

 while all those in the other half are carried further from it. The 

 ebb-current force has its greatest intensity at the equator, and 

 diminishes very gradually on both sides of it, since the parallel 

 circles in low latitudes become only gradually smaller. Only in 

 high latitudes, where the circles diminish rapidly, does the force 

 of the ebb-current quickly diminish ; and only at the poles does 

 it entirely cease. 



Since, as we have shown, the flood rises more above the nor- 



! 



