BOTTOM OF THE SEA. 31 



though an enclosed sea, receives so few great rivers in 

 proportion to its surface, and is exposed to such im- 

 mense waste by evaporation in a southern climate, 

 that it is lower than the Atlantic, from which a strong 

 current sets constantly through the Straits of Gibraltar. 

 One of the most remarkable instances known of the 

 inequality of level between neighbouring seas is that 

 stated to exist between the Red Sea at Suez, and the 

 nearest point of the Mediterranean, the former being 

 thirty-two feet higher than the latter. The difference 

 of level between the waters at opposite sides of the 

 Isthmus of Panama has been said to be of equal or 

 greater amount, but recent measurements throw doubt 

 on the statement ; and possibly the level of the Red 

 Sea may also have been incorrectly computed. It is, 

 however, reasonable to attribute to the form and posi- 

 tion of masses of land, to the presence or absence of 

 great inflowing rivers, to the climatic relations of in- 

 closed seas of moderate extent, and to the nature of 

 the sea-bottom, small inequalities of level producing 

 superficial currents. 



The bottom of the sea appears to be as greatly di- 

 versified as the surface of the land. Were the bed of 

 the ocean laid bare, we should find mountains of vast 

 height, whose points now are alone known to us, in 

 the islands which stud the face of the great Pacific 

 Ocean. Round many volcanic islands the circling 

 cliffs go sheer down, into an unfathomable abyss; such 

 would therefore rise like columns, possibly twenty or 

 thirty thousand feet in height. Shoals, deprived of 

 water, would become table-lands, with deep valleys or 



