Mary McGrath, age 13, of Peoria, Illinois, for her question:

What is meant by the horse latitudes?

In olden times, sailing ships used the power of the wind to blow them along. But winds are fickle and sailing long voyages was risky. Mariners learned about the steady prevailing winds that circle in wide belts around the globe. But even the planetary winds were not dependable. In some regions, they blew hardly at all.

Atlantic sailors ran into one of these regions of calm along Latitude 30 degrees north of the equator. Their sails sagged and their ships stayed motionless for days and sometimes weeks, while stores of food and fresh water were consumed. The trading vessels often shipped horses and when food and fresh water ran low, they were thrown overboard. This region became known as the horse latitudes because the bloated bodies of these animals floated in the calm sea. The horse latitudes lie between the prevailing westerlies and the trade winds. A similar belt of calm lies along Latitude 30 degrees south of the equator.