HISTORY OF 



lower neap-tides have their production. In a 

 word, the tides are greatest in the syzigies, and 

 least in the quadratures. 



This theory well understood, and the astrono- 

 mical terms previously known, it may readily be 

 brought to explain the various appearances of the 

 tides, if the earth were covered with a deep sea, 

 and the waters uninfluenced by shoals, currents, 

 straits, or tempests. But in every part of the sea 

 near the shores, the geographer must come in to 

 correct the calculations of the astronomer. For, 

 by reason of the shallowness of some places, and 

 the narrowness of the straits in others, there 

 arises a great diversity in the effect, not to be ac- 

 counted for without an exact knowledge of all 

 the circumstances of the place. In the great 

 depths of the ocean, for instance, a very slow and 

 imperceptible motion of the whole body of water 

 will suffice to raise its surface several feet high ; 

 but if the same increase of water is to be con- 

 veyed through a narrow channel, it must rush 

 through it with the most impetuous rapidity. 

 Thus, in the. English Channel, and the German 

 Ocean, the tide is found to flow strongest in those 

 places that are narrowest ; the same quantity of 

 water being, in this case, driven through a 

 smaller passage. It is often seen, therefore, 

 pouring through a strait with great force ; and, 

 by its rapidity, considerably raised above the sur- 

 face of that part of the ocean into which it runs. 



This shallowness and narrowness in many parts 

 of the sea, give also rise to a peculiarity in the 

 tides of some parts of the world. For in many 



