ned by apprenticeship or by being
the son of a member.

Foreign trade was revived because it was a period of comparative
peace. The nation sought to sell as much as possible to foreign
nations and to buy at little as possible and thereby increase its
wealth in gold and silver, which could be used for currency.

Ships weighed 200 tons and had twice the cargo space they had
previously. Their bows were more pointed and their high prows made
them better able to withstand gales. The mariners' compass with a
pivoting needle and circular dial with a scale was introduced. The
scale gave precision to directions. Ships had three masts. On the
first was a square sail. On the second was a square sail with a
small rectangular sail above it. On the third was a three cornered
lateen sail. These sails make it possible to sail in almost any
direction. This opened the seas of the world to navigation. At
this time navigators kept their knowledge and expertise secret
from others. Adventurous seamen went on voyages of discovery, such
as John Cabot to North America in 1497, following Italian
Christopher Columbus' discovery of the new world in 1492.
Ferdinand Magellan of Portugal circumnavigated the world in 1519,
proving uncontrovertedly that the earth was spherical rather than
flat. Sailors overcame their fear of tumbling into one of the
openings into hell that they believed were far out into the
Atlantic Ocean and ceased to believe that a red sunset in the
morning was due to a reflection from hell. Seamen could venture
forth into the darkness of the broad Atlantic Ocean with a fair
expectation of finding their way home again. They gradually
learned that there were no sea serpents or monsters that would
devour foolhardy mariners. They learned to endure months at sea on
a diet of salt beef, beans, biscuits, and stale water and the bare
deck for a bed. But there were still mutinies and disobedient
pilots. Mortality rates among seamen were high. Theologians had to
admit that Jerusalem was not the center of the world. There are
more navy ships, and they have some cannon.

The blast furnace was introduced in the iron industry. A blast of
hot air was constantly forced from a stove into the lower part of
the furnace which was heating at high temperature a mixture of the
iron ore and a reducing agent that combined with the oxygen
released. After the iron was extracted, it was allowed to harden
and then reheated and hammered on an anvil to shap