Mare Clausum

• Mare Clausum (closed sea) in Ancient Rome and Greece, meant that the seas were closed to shipping.
• Mare liberum meant that the seas were open to shipping. However, it appears that some merchant vessels sailed all year round.

Hesiod (8th century BCE)

• Hesiod in ‘Works and Days’, written in the eighth century BCE, divided sailing into four seasons:
  1. The seas opened in the Spring when the top leaves of the Fig tree had sprouted.
  2. An unsafe period for sailing between Spring and Autumn.
  3. A safe period for sailing of 50 days after the summer solstice (22 June).
  4. The seas were closed at the setting of the constellation Hydra, and all vessels pulled out of the water.

Vegetius (5th century CE)

• Writing in the 5th century CE, Vegetius also divided sailing into four seasons, like Hesiod before him.
  • The seas were closed 3 days before the 13th November the Ides of November.
  • The seas were reopened 6 days before 15th March the Ides of March.