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Age of Discovery

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Age of Discovery

Sailing & exploration technologies

magnetic compass

  • a magnetized needle or, originally, "spoon," that can freely rotate on a hard surface, pin, or in water
    • its magnetic tip will rotate to point north or south
  • a compass is used for navigation
    • as it can indicate a boat's direction without knowing the time of day or in poor weather or the dark
  • invented in China, the compass spread to the middle east and Europe by the 13th century
    • the first Chinese compasses were made with "lodestone"
      • = naturally magnetized iron stone
  • iron needles were later used by magnetizing their point with a lodestone
    • the needle could be suspended in water, and it would turn to point to one of the earths' magnetic poles (north or south)
  • it is possible that the Europeans had a distinct invention of the compass
    • either way, they adapted the "dry compass"
    • = suspending the magnetized needle on a pin so that it could rotate freely
  • click EXPAND for a late 12th century description of an early compass by Alexander Neckam, an Englishman who worked with magnetics:

The sailors, moreover, as they sail over the sea, when in cloudy whether they can no longer profit by the light of the sun, or when the world is wrapped up in the darkness of the shades of night, and they are ignorant to what point of the compass their ship's course is directed, they touch the magnet with a needle, which (the needle) is whirled round in a circle until, when its motion ceases, its point looks direct to the north.

from History of the compass (wikipedia)

  • use of the compass greatly facilitated long-distance ocean travel
    • and allowed for creation of accurate maps

Scurvy

  • a deadly condition resulting from a lack of Vitamin C
  • on long voyages, European ships generally carried for food:
    • salted pork or other meats, called "jerky"
    • salted hard bread, called "hardtack"
    • these foods are "cured" by salt or cooking/ drying / smoking in order to remain edible over long voyages
      • salt "cures" food by removing water and destroying bacteria
      • cooking preserves bread by removing bacteria and water
  • scurvy was accepted as an unavoidable condition sailors would face on long distance voyages
  • however, tropical fruits and their juices, especially lemon and lime, have a long "shelf life" and have high concentrations of Vitamin C
  • by the time of Vasco de Gama's expedition around Africa, Portuguese explorers were aware of the ability of citrus to prevent scurvy
    • nevertheless, de Gama and other explorers lost over half and sometimes almost all of their crew (sailors) to scurvy
    • Europeans continued to think that scurvy was a "digestive" disease and ignored the curative effects of citrus
      • and not until the late 1750s did the British Royal Navy adopt the practice of giving sailor Vitamin C-rich lemon juice
  • in 1535, French explorer Jacques Cartier's crew was afflicted by scurvy during the first European winter stay in Canada
    • local Indians saved them by introducing them to brewed pine needles / pine buds
      • that Native Americans had traditionally used as a source of Vitamin C
    • Cartier brought this technology back to France, and it was adopted by other explorers
    • see Spruce beer

Portugal

Technologies & cultural experience in sailing

People & explorers

Henry the Navigator

Bartolomeu Dias

King Manuel I

Bartalemu

Vasco de Gama

  • Portugal sources:

https://pt.wikipedia.org/wiki/Livro_das_Armadas https://pt.wikipedia.org/wiki/Descobrimentos_portugueses

Sources

Mitchell]

    • this "web-book" has succinct, well-organized chapters in chronological order
    • can be an excellent and appropriate source for students
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