The whole poem is in Murray's English edition, Vol.IV.p.207.

Of it we quote the following.

The reader will bear in mind that it is addressed to Lady Byron on a sick-bed:-- 'I am too well avenged, but 't was my right; Whate'er my sins might be, _thou_ wert not sent To be the Nemesis that should requite, Nor did Heaven choose so near an instrument.
Mercy is for the merciful! If thou Hast been of such, 't will be accorded now.
Thy nights are banished from the realms of sleep, For thou art pillowed on a curse too deep; Yes! they may flatter thee, but thou shalt feel A hollow agony that will not heal.
Thou hast sown in my sorrow, and must reap The bitter harvest in a woe as real.
_I have had many foes, but none like thee_; For 'gainst the rest myself I could defend, And be avenged, or turn them into friend; But thou, in safe implacability, Hast naught to dread,--in thy own weakness shielded, And in my love, which hath but too much yielded, And spared, for thy sake, some I should not spare.
And thus upon the world, trust in thy truth, And the wild fame of my ungoverned youth,-- On things that were not and on things that are,-- Even upon such a basis thou halt built A monument whose cement hath been guilt! The moral Clytemnestra of thy lord, And hewed down with an unsuspected sword Fame, peace, and hope, and all that better life Which, but for this cold treason of thy heart, Might yet have risen from the grave of strife And found a nobler duty than to part.
But of thy virtues thou didst make a vice, Trafficking in them with a purpose cold, And buying others' woes at any price, For present anger and for future gold; And thus, once entered into crooked ways, The early truth, that was thy proper praise, Did not still walk beside thee, but at times, And with a breast unknowing its own crimes, Deceits, averments incompatible, Equivocations, and the thoughts that dwell _In Janus spirits, the significant eye That learns to lie with silence_, {14} the pretext Of prudence with advantages annexed, The acquiescence in all things that tend, No matter how, to the desired end,-- All found a place in thy philosophy.
The means were worthy and the end is won.
I would not do to thee as thou hast done.' Now, if this language means anything, it means, in plain terms, that, whereas, in her early days, Lady Byron was peculiarly characterised by truthfulness, she has in her recent dealings with him acted the part of a liar,--that she is not only a liar, but that she lies for cruel means and malignant purposes,--that she is a moral assassin, and her treatment of her husband has been like that of the most detestable murderess and adulteress of ancient history, that she has learned to lie skilfully and artfully, that she equivocates, says incompatible things, and crosses her own tracks,--that she is double-faced, and has the art to lie even by silence, and that she has become wholly unscrupulous, and acquiesces in _any_thing, no matter what, that tends to the desired end, and that end the destruction of her husband.

This is a brief summary of the story that Byron made it his life's business to spread through society, to propagate and make converts to during his life, and which has been in substance reasserted by 'Blackwood' in a recent article this year.
Now, the reader will please to notice that this poem is dated in September 1816, and that on the 29th of March of that same year, he had thought proper to tell quite another story.

At that time the deed of separation was not signed, and negotiations between Lady Byron, acting by legal counsel, and himself were still pending.