THE EARTH AS IT IS. 89 



cles and masses, runs down all declivities in streams 

 small and large toward the ocean, and is agitated by the 

 winds and the tides. Xot only is its motion kept up in 

 these ways, but there are great systematic currents in the 

 ocean, which maintain a free circulation between differ- 

 ent quarters of the globe, and exert a marked influence 

 upon the climates of many countries. The great Gulf 

 Stream is one of these currents. By all of these means 

 of motion there is secured a circulation of water in the 

 earth which in its system and thoroughness bears an 

 analogy to the circulation of the blood in the body. 

 What extensive and varied effects it produces in this 

 circulation upon the solid materials of the earth's surface 

 you will learn in succeeding chapters. 



169. How the Earth's Surface is Diversified. I have 

 already spoken of some of the grand features of the 

 earth's surface. But there are subordinate features 

 which diversify it greatly bluffs, hills of various con- 

 tours, valleys with and without streams, collections of 

 rock differing in arrangement, shape, and color, some be- 

 ing stratified and others not ; rocks jutting out from the 

 ground, boulders of various sizes, etc. A material addi- 

 tion is made to this diversity by water every where en- 

 livening the scene by its motion in obedience to every 

 impulse. And then we have life, with its endless varie- 

 ty of shape, and color, and motion. 



170. Treasures in the Crust of the Earth. As you have 

 already seen, there are precious treasures of every varie- 

 ty scattered among the rocks, and earth, and sand of the 

 globe for the use of man. There are immense stores of 

 coal ; metals of every kind, and in quantities suited to the 

 amount of uses to which they can be appropriated j pre- 

 cious gems of every quality and hue ; granite, sandstone, 

 marble, etc., for building ; clay for pottery and bricks, 

 etc. 



