EISE OF THE WAVE. 29 



arrangement of the land and sea. The up-drawing 

 of a perfect tide-wave requires that the moon, or the 

 moon and sun together, should stand on the zenith 

 of some point in the sea (that is to say, right over 

 the head of the observer at that point), while for 

 two other points, or at least for one, of the same 

 sea they must be just on the horizon. At such 

 latter point the tide is at the lowest, just when it 

 is at the highest at the former. From this it is 

 evident, that neither the inland seas or lakes, nor 

 small seas in general, can be subject to a tide of 

 their own. Even the Atlantic Ocean is not broad 

 enough for the formation of a powerful tide-wave. 

 The breadth of tins ocean near the equator amounts 

 to forty or fifty degrees, or about one-eighth of the 

 circumference of the earth. But the curvature of 

 the earth's surface is far from being great enough 

 to allow of any considerable difference between the 

 distances of our satellite from any different points 

 of tins sea. Only the great Pacific Ocean, whose 

 enormous mass of water embraces nearly half the 

 globe, has width enough for this. The Pacific 

 therefbie is the sea from which the tides chiefly 

 come forth. The tide-wave once formed, marches 

 on from this ocean, towards the west, according 

 to the same laws which govern the path of any 

 other wave, which may be raised on any surface of 

 water, whether by the wind, by a stone thrown in, 

 or by any other cause. It reaches the Indian 



