Answer:
"their eyes purging thick amber and plum-tree gum".
Step-by-step explanation:
A metaphor is the figurative language technique of comparing things without the use of "like" or "as" in a sentence. It compares two things that may not be alike but have some sort of similarity between them.
In the given excerpt from Act 2 scene ii of William Shakespeare's "Hamlet", the protagonist Hamlet uses a metaphor while talking about the words of the writer of the book he was reading. The writer of the book says that the eyes of old men "purg[e] thick amber and plum-tree gum". This metaphorically states the eyes of old men who are filled with gunk and have wrinkled faces.
Thus, the metaphor in the given excerpt is "their eyes purging thick amber and plum-tree gum".