Now, I think by altering the punctuation, the sense of the passage is at once made apparent, as thus,—
"If it were done when 'tis done then 'twere well.
It were done quickly, if the assassination
Could trammel up the consequence, and catch,
With his surcease, success, that but this blow
Might be the be-all and the end all here," &c.
but to make use of a paradox, it is not done when it is done; for this reason, there is the conscience to torment the evil-doer while living, and the dread of punishment in another world after death: the "bank and shoal of time" refers to the interval between life and death, and to "jump" the life to come is to hazard it. The same thought occurs in Hamlet, when he alludes to—
"That undiscovered country, from whose bourne
No traveller returns."
But that is clear enough, as in all probability the annotators left the passage as they found it. I have not the opportunity of consulting Mr. Collier's edition of Shakespeare, so that I am unaware of the manner in which he renders it; perhaps I ought to have done so before I troubled you. Possibly some of your readers may be disposed to coincide with me in the "new reading;" and if not, so to explain it that it may be shown it is my own obscurity, and not Shakespeare's, with which I ought to cavil.