THE WORLD'S WONDERS. 37 



the rapid rotary motion of descending currents, and in the equa- 

 torial regions they often deluge and desolate vast tracts of land, 

 destroying buildings and stock, and sometimes washing up large 

 trees. 



FORMATION OF ISLANDS. 



NINE-TENTHS of the islands which dot the ocean lie within the 

 tropics. These islands are divided into two great classes. The 

 one class is of volcanic origin, upheaved from the depth of the 

 ocean ; or, rather, they are lofty peaks of mountains, whose 

 sides and bases lie deep in the water. There are two opposite 

 theories to account for the existence and present appearance of 

 these islands. According to one theory, a continent once occu- 

 pied a large portion of the Pacific Ocean within the tropics, a 

 large portion of which has sunk beneath the water, and these 

 islands are but the peaks and table lands of that lost continent. 

 The other theory is that these islands have been for unknown 

 ages, and now are, slowly being lifted up from the depth below. 

 Both theories rest upon so wide an induction of facts that both 

 may be accepted as true ; or rather as parts of the one great 

 truth, that the crust of the earth, which we are wont to consider 

 so firm and stable, is now, as it always has been, rising and 

 falling, as truly as the surface of the water rises and falls by 

 the attraction of the sun and moon ; only that these periodic 

 changes are measured by ages instead of by hours. "NY ho shall 

 say that in the higher knowledge which we shall gain during the 

 ages of the future we may not attain to the understanding that 

 the rise and sinking of continents is like that of the tides, gov- 

 erned by law, and that we may not be able to express in figures, 

 which will then be quite finite to us. though now seeming infinite, 

 the years that have elapsed since " heaven and earth rose out of 

 chaos !" 



Volcanic islands are found in all oceans. Iceland nas its 

 Heckla, Sicily its JEtna, Hawaii its Mauna Kea and Mauna Loa> 

 Niphon its Fusiyama. From Sumatra, Java and Sumbawa, 

 Ternate and Tidore, Borneo, Celebes and Gilolo, close by the 

 equator, thence northward and north-westward to the Kurile 



