404 Dr. J. R. Mayer on Celestial Dynamics* 



consequence of which the flow of the tidal wave is delayed, and 

 high water occurs in the open sea on the average about 2^ 

 hours after the transit of the moon through the meridian of 

 the place. 



The waters of the ocean move from west and east towards the 

 meridian of the moon, and the more elevated wave is, for the 

 reason above stated, always to the east of the moon's meridian ; 

 hence the sea must press and flow more powerfully from east to 

 west than from west to east. The ebb and flow of the tidal 

 wave therefore consists not only in an alternate rising and falling 

 of the waters, but also in a slow progressive motion from east 

 to west. The tidal wave produces a general westerly current in 

 the ocean. 



This current is opposite in direction to the earth's rotation, 

 and therefore its friction against and collision with the bed 

 and shores of the ocean must offer everywhere resistance to the 

 axial rotation of the earth, and diminish the vis viva of its 

 motion. The earth here plays the part of a fly-wheel. The 

 moveable parts of its surface adhere, so to speak, to the rela- 

 tively fixed moon, and are dragged in a direction opposite to 

 that of the earth's rotation, in consequence of which, action 

 takes place between the solid and liquid parts of this fly-wheel, 

 resistance is overcome, and the given rotatory effect diminished. 



Water-mills have been turned by the action of the tides; the 

 effects produced by such an arrangement are distinguished in a 

 remarkable manner from those of a mill turned by a mountain- 

 stream. The one obtains the vis viva with which it works from 

 the earth's rotation, the other from the sun's radiation. 



Various causes combine to incessantly maintain, partly in an 

 undulatory, partly in a progressive motion, the waters of the 

 ocean. Besides the influence of the sun and the moon on 

 the rotating earth, mention must be made of the influence of 

 the movement of the lower strata of the atmosphere on the sur- 

 face of the ocean, and of the different temperatures of the sea 

 in various climates ; the configuration of the shores and the bed 

 of the ocean likewise exercise a manifold influence on the ve- 

 locity, direction, and extent of the oceanic currents. 



The motions in our atmosphere, as well as those of the 

 ocean, presuppose the existence and consumption of vis viva 

 to overcome the continual resistances, and to prevent a state of 

 rest or equilibrium. Generally speaking, the power necessary 

 for the production of aerial currents may be of threefold origin. 

 Either the radiation of the sun, the heat derived from a store 

 in the interior of the earth, or, lastly, the rotatory effect of the 

 earth may be the source. 



As far as quantity is concerned, the sun is by far the most im- 



