INTRODUCTION. 



THE world is a great book, and he who walks or 

 rides may read. We cannot get inside the earth ; and 

 so it happens we do not know positively how it looks 

 within the thin crust on which we live, nor can we, 

 except in a very uncertain way, know of what the in- 

 terior is made or in what condition it may be. This 

 is not of much consequence ; because the outside of 

 the world, the part we call the ground, and the things 

 upon it, are quite enough to take all our attention. 

 Upon the surface of the world are the great seas, the 

 mountains, the plains and rivers ; and among these 

 things we spend our lives. It is not very convenient 

 to get off the ground, except for a few hours in a 

 balloon : so it happens we must at all times remain on 

 the surface of this great and wonderful book called the 

 Earth or the World. We might board a steamer, and 

 sail upon the sea, and soon lose sight of the land, 

 and yet all the time we would be comparatively near 

 the ground. Beneath the deepest seas is still the solid 

 ground ; and the ship merely floats above the crust of 

 the earth, upon the water. In a few places, men in 



