Answer: as a dungeon of flames that give off no light.
<em>Paradise Lost</em> is an epic poem by John Milton, written in the 17th century. It is considered one of Milton's best works. It describes the "Fall of Man" as told in the Bible (the story of Adam and Eve and their expulsion from The Garden of Eden).
The book begins with Satan and his demons, who are chained to a lake of fire in Hell. Hell is describes as a dungeon of flames that give off no light.
In Dulce et Decorum Est, hags is used to describe young soldiers. The simile 'coughing like hags' was used because the young soldiers went into battle strong and full of life. After battle, they returned looking aged and beat down - hence 'hags' or resembling beggars.
I believe it is the compass. It aided sailors locate the direction to which they needed to go. Even before the age of exploration, people had ships capable of long voyages. As the years pass, the designed improved to an extent that they can travel farther.
"Are you sure you don't want to wear that?"