Answer:
Their eyes purging thick amber and plum-tree gum.
Explanation:
William Shakespeare's "Hamlet" is the story of revenge taken by the young Hamlet on his father's killer, his uncle Claudius. Claudius had not only taken the kingship but also married the wife of his own brother King Hamlet, Gertrude.
The provided excerpt from Act II is from the scene where Polonius had tried to show or proof the insanity of Hamlet to King Claudius and Gertrude. The metaphor in this excerpt is "Their eyes purging thick amber and plum-tree gum". This is a description of the book's contents that he was reading, to Polonius. Metaphors are words used to compare one thing with another, but which is not literally applicable. So, the metaphor uses words like "purging thick amber and plum tree-gum" which is impossible to happen in the real world. It is just a metaphorical comparison of old people.
