What is the significance of the following lines:
"Thou art too like the spirit of Banquo. Down!
Thy crown does sear mine eyeballs. And thy hair,
Thou other gold bound brow, is like the first.
A third is like the former.--Filthy hags,
Why do you show me this? -A fourth? Start, eyes!
Another yet? A seventh? I'll see no more.
And yet the eighth appears who bears a glass
Which shows me many more, and some I see
That twofold balls and treble scepters carry"