104 PHYSICAL GEOGRAPHY. 



site currents ; sometimes their cause is inexplicable. The 

 Maelstroom of Norway is a very celebrated whirlpool.* 



OF THE CHANGES ON THE EARTH'S SURFACE. 



That a change has taken place on the earth, and is 

 continuing to do so, is most strikingly evident. The in- 

 road made by the sea on the land cannot but be noticed 

 even by a casual walker on the sea side. But a more 

 powerful agent has been engaged in this work than the 

 mere action of the waves, and this may probably to 

 a certain extent be fire. By the industry of geologists 

 it has been ascertained that the greater part of Europe 

 was at one time underneath the surface of the water. 

 Indeed the whole of the Northern hemisphere is said to 

 have resembled a great ocean interspersed with islands. 

 The whole of Italy and Sicily was at one time under- 

 neath the water, as also a large portion of Spain, France, 

 Germany, Russia, England, and other countries. The 

 Apennines have been raised from 1 ,000 to "2,000 feet ; 

 the Alps from 2,000 to 4,000 ; and the Pyrenees have 

 acquired the whole of their altitudes since the origin of 

 some of the secondary strata.f Some geologists ima- 

 gine that this rising of the land is still progressing in 

 certain places. The depth of the Baltic J and Black Sea 

 has been found to decrease gradually, as also that of the 

 North Sea or German Ocean, which is supposed by some 

 to be produced by the upheaving of the bottom. 



Volcanic action has been very effective in altering the 

 face of the Earth. It has been already observed, that 

 nearly half of the islands are of volcanic origin ; and 

 since the middle of the last century, six mountains, of 



* At certain times, particularly in stormy weather, it is dangerous to 

 venture within five or six miles of the Maelstroom, as vessels have often 

 been absorbed by it. Whales have frequently come within the range 

 of its vortex, and have been carried down into it. Trees have been 

 purposely sent down the vortex, and after a considerable time they 

 have risen again, shattered and crushed as if they had been dashed 

 against the rocks. 



f See Lyell's Geology. 



j The Baltic sea is said to decrease in depth at the rate of one foot 

 in 25 years. 



