12 THE OCEAlf. 



liim from the overwhelming wave. Through the 

 Pentland Firth, 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 

 srnallness 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 ebbmgs 

 and flowings cf 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 tiooi-tide permitting ships to sail up 

 rivers, even wdien the wind is adverse, and often 

 admitting deep vessels to j)ass into harbours, over 

 banks or bars, impassable at the ordinary depth of tha 

 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 we may say, in the sea, whose 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 Picef, 

 increasing in force, till it rushes witli amazing 



