Harry S. Truman: Thirty-Third President of the United States Book

For many years sailors knew how to measure latitude for their location of north or south of the equator. But they could not measure longitude of their location east or west of their home. This caused many people to die because getting to a certain location was hard. To solve this problem a certain clock was made so that this wouldn't happen anymore. John Harrison worked for more than forty years to create the perfect clock.

This picture book is great for introducing longitude and latitude to an elementary class. Something that I would read before learning that lesson. The pictures are also fun to look at.