The earth isn't really any larger now than it was thousands of years ago. But the part that people know about has grown bigger. Now the floor of the deep sea is the only large part of the earth that no one has ever visited. Explorers have gone almost everywhere else.
   Explorers have set out on their travels for many different reasons. Some were just curious. Some hoped to discover better ways of reaching such places as the Spice Islands and India.
   Some explorers were missionaries. Some wanted to help build big empires. Some were scientists who wanted to make new discoveries. Some hoped to find great riches. Some just loved adventure.
   Exploring unknown parts of the world is never easy. Explorers suffer great hardships. Many have died before they could get back to tell what they had found.
   It is not always easy to be sure of what an explorer actually found out. Many early explorers mixed stories they made up with true stories. But some of the strangest stories the early explorers told were true.
The chart on the next page gives the names of some of the most famous explor­ers. It tells, too, a little about what they did.