Prince Henry the Navigator: Tools That Transformed Sailing

Introduction: Portugal's Drive for Exploration

Spain and Portugal were two nations that led the way in exploration and discovery, especially during the fourteenth and fifteenth centuries. Each country had its successes and its failures, and each country had its famous explorers. The focus of this paper is one particular Portuguese explorer, Prince Henry the Navigator, and the tools and techniques he introduced to his sailors, which revolutionized sailing and furthered exploration more than anyone else had done up to that point. Although Henry himself never actually set sail on these adventures, "under his direction many important expeditions were undertaken along the west coast of Africa."

Henry was the son of Joao I, the king of Portugal at the time, and was driven to help his father find a faster route to the spice trade in the Far East. The Italians and the Arabs already had strong footholds there, and Henry wanted to ensure that Portugal gained one as well, so that they might partake of the riches in slaves, spices, and gold to be had there.

Henry's School for Navigators at Sagres

The Portuguese are an adventurous people, and Henry knew that if he could capitalize on this, he could drive his sailors to go farther and accomplish more than anyone else had done up to that point. From the Muslims, the Portuguese "had learned better ship design, cartography, sailing, and navigation and math skills." To that end, Henry established an observatory and the first school for navigators in Sagres, Portugal, where he lived.

Before the sailors could be taught anything new, however, Henry had to work to convince them that their fears would not come to pass. "Expeditions moved slowly due to the sailors' belief that waters at the equator were at the boiling point, that human skin turned black, and that sea monsters would engulf ships." Henry could have reasoned that by knowing the seas better, his men would not be so afraid of the unseen dangers that lurked there. After all, it is human nature to fear what we do not know. Often, once the mystery surrounding something is revealed, the fear dissipates as well.

Dead Reckoning and the Magnetic Compass

One new navigation tool Henry introduced was dead reckoning, in which a sailor essentially deduces his way across the ocean. As Pickering explains:

In dead reckoning, the navigator finds his position by measuring the course and distance he has sailed from some known point. Starting from a known point, such as a port, the navigator measures out his course and distance from that point on a chart, pricking the chart with a pin to mark the new position. Each day's ending position would be the starting point for the next day's course-and-distance measurement.

This method does not always work, however, especially when there is no known point from which to begin the calculation — for example, when visibility is poor to nonexistent due to clouds, rain, or fog. To overcome this problem, Henry introduced the magnetic compass to his sailors. The magnetic compass was actually invented by the Chinese long before, but Henry made it widely used among Portuguese navigators. A magnetic compass works as follows: a piece of naturally occurring magnetite (usually in the form of a lodestone) is attached to one end of a wooden stick and floated in a pool of water. The magnetized stick orients itself to Earth's magnetic field, rotating until the lodestone end points north. "The magnetic compass, therefore, provided navigators with a fixed reference point regardless of their location, the boat's heading, the wind direction, or the state of visibility."