—Come what come may,
Time! on!—the hour runs thro' the roughest day.
Macbeth is deliberating upon the events which are to befall him; but finding no satisfaction from his own thoughts, he grows impatient of reflection, and resolves to wait the close without harassing himself with conjectures:
—Come what come may.
But, to shorten the pain of suspense, he calls upon time, in the usual style of ardent desire, to quicken his motion,
Time! on!—
He then comforts himself with the reflection that all his perplexity must have an end,
—The hour runs thro' the roughest day.
This conjecture is supported by the passage in the letter to his lady, in which he says, They referr'd me to the coming on of time with, Hail, King that shall be.