Read the excerpt from Act II of Hamlet. I have of late,—but wherefore I know not,—lost all my mirth, forgone all custom of exercises; and indeed it goes so heavily with my disposition that this goodly frame, the earth, seems to me a sterile promontory; this most excellent canopy, the air, look you, this brave o’erhanging firmament, this majestical roof fretted with golden fire, why, it appears no other thing to me but a foul and pestilent congregation of vapours.

What is the effect of Hamlet’s use of metaphors in this excerpt?