Please explain this quote from Macbeth:
Now o'er the one half-world Nature seems dead, and wicked dreams abuse The curtain'd sleep; witchcraft celebrates Pale Hecate's offerings; and wither'd Murder,(60) Alarum'd by his sentinel, the wolf, Whose howl's his watch, thus with his stealthy pace, With Tarquin's ravishing strides, towards his design Moves like a ghost. Thou sure and firm-set earth, Hear not my steps, which way they walk, for fear(65) Thy very stones prate of my whereabout, And take the present horror from the time, Which now
This soliloquy of Macbeth's continues the motif of phantasmagoria along with the theme of "fair is foul/foul is fair" as Macbeth senses the influence of the preternatural world. He remarks in the first two lines cited that at this time of day, dreams deceive and the witches celebrate offerings to the goddess of magic, Hecate. The use of the trochaic in the middle of the line where eyes and now meet--"...eyes. Now o'er the one half-world..."--creates an emphasis upon the idea as dark imagery pervades the next several lines.
Macbeth ironically alludes to a Roman tyrant, Tarquin, who slay Lucrece, in anticipation of his dastardly deed, perhaps subconsciously comparing himself. The line about Murder's sentinel, the wolf, denotes the passing of time for murder. This line continues the phantasmagoria motif as Murder stalks like a ghost. Then, the line "Thou sure and firm-set earth" sets up a contrast between the preternatural world and the earthly one. Macbeth gains in resolve and determines to go through with the act of murdering Duncan. He hopes that the stones will not "tattle" (prate) on him as he steals forth. In the first foot of verse, the line scans as a spondee, giving equal emphasis to the first two syllables and the word Hear. In the last line cited, the verb take means remove; present denotes immediate; and, time connotes night and opportunity. (Remove the horrible silence which suits this opportunity.) Clearly, Macbeth's misgivings at the beginning of his soliloquy have been quelled by his ambitions.