"trireme in the Mediterranean"

A trireme was a type of galley warship, named for its three banks of oars on each side. Used by the Phoenicians, ancient Greeks and Romans, it was the dominant warship in the Mediterranean from the 7th to the 4th centuries BC.  Even after larger ships were introduced, the trireme remained an important workhorse of the Roman Navy.

 

Model of a Roman trireme
Public DomainModel of a Roman trireme - Credit: Gaston Braun

A similar passage can be found in Conrad's memoir, The Mirror of the Sea (1906), describing the feelings of 'the commander of the first Roman galley' to sail up the Thames.