24 THE OCEAN. 



him from the overwhelming wave. Through the 

 Pentland Frith, between Scotland and the Orkney 

 Islands, the spring- tide rushes at the rate of nine 

 miles an hour. The tide in inland seas is so slight 

 as to be scarcely observable, probably owing to the 

 smallness of the volume of water which they con- 

 tain ; and hence the astonishment which the soldiers 

 of Alexander, accustomed to the equable condition 

 of the Mediterranean, felt, when at the mouth of 

 the Indus, they beheld the sea swell to the height 

 of thirty feet. 



That some purpose, important in the constitution 

 of our world, is effected by these periodical ebbings 

 and flowing, of the mighty sea, is highly probable; 

 but our acquaintance with the arcana of nature is 

 too slight to point it out. In navigation they are 

 useful; the flood-tide permitting ships to sail up 

 rivers, even when the wind is adverse, and often 

 admitting deep vessels to pass into harbors, over 

 banks or bars, impassable at the ordinary depth of 

 the water. 



Besides the tides, the sea has other motions of 

 great regularity, called currents. The principal of 

 these is the notable Gulf-stream, a strong and rapid 

 river, as I may say, in the sea, wlx>se banks are 

 almost as well defined as if they were formed of 

 solid earth, instead of the same fickle fluid as the 

 torrent itself. It first becomes appreciable on the 

 western coast of Florida, gently flowing southward 

 until it reaches the Tortugas, when it bends its 

 course easterly, and runs along the Florida Reef, 

 increasing in force, till it rushes with amazing 



