London Bridge is falling down falling down falling down
Poi s’ascose nel foco che gli affina
Quando fiam ceu chelidon—O swallow swallow
Le Prince d’Aquitaine à la tour abolie
These fragments I have shored against my ruins
Why then Ile fit you. Hieronymo’s mad againe.
Datta. Dayadhvam. Damyata.
Shantih shantih shantih
While the civilization is crumbling, the poet has "saved" some fragments from his "ruins" from which he seeks light for a lasting peace.
Yes, this is only 'one' interpretation of the closing lines but, to me, the most valid so far.
I hold fast to Cleanth Brooks' interpretation of the closing llines (quoted above) and oppose it to yours which chooses to look only at the negative aspect of things -- "violence, chaos and murder" -- closing eyes to what positive might emerge out of them, so as to make what Yeats aptly called "a vineyard of the curse". 
Here's the relevant excerpt from Brooks: 
The bundle of quotations with which the poem ends has a very definite relation to the general theme of the poem and to several of the major symbols used in the poem. Before Arnaut leaps back into the refining fire of Purgatory with joy he says: "I am Arnaut who weep and go singing; contrite I see my past folly, and joyful I see before me the day I hope for. Now I pray you by that virtue which guides you to the summit of the stair, at times be mindful of my pain." This theme is carried forward by the quotation from Pervigilium Veneris: "When shall I be like the swallow." The allusion is also connected with the Philomela symbol. (Eliot's note on the passage indicates this clearly.) The sister of Philomela was changed into a swallow as Philomela was changed into a nightingale. The protagonist is asking therefore when shall the spring, the time of love, return, but also when will he be reborn out of his sufferings, and--with the special meaning which the symbol takes on from the preceding Dante quotation and from the earlier contexts already discussed--he is asking what is asked at the end of one of the minor poems: "When will Time flow away."
The quotation from "El Desdichado," as Edmund Wilson has pointed out, indicates that the protagonist of the poem has been disinherited, robbed of his tradition. The ruined tower is perhaps also the Perilous Chapel, "only the wind's home," and it is also the whole tradition in decay. The protagonist resolves to claim his tradition and rehabilitate it.
The quotation from The Spanish Tragedy--"Why then Ile fit you. Hieronymo's mad againe"--is perhaps the most puzzling of all these quotations. It means, I believe, this: The protagonist's acceptance of what is in reality the deepest truth will seem to the present world mere madness. ("And still she cried . . . 'Jug jug' to dirty ears.") Hieronymo in the play, like Hamlet, was "mad" for a purpose. The protagonist is conscious of the interpretation which will be placed on the words which follow--words which will seem to many apparently meaningless babble, but which contain the oldest and most permanent truth of the race:
Datta. Dayadhvam. Damyata.
Quotation of the whole context from which the line is taken confirms this interpretation. Hieronymo, asked to write a play for the court's entertainment, replies:
Why then, I'll fit you; say no more.
When I was young, I gave my mind
And plied myself to fruitless poetry;
Which though it profit the professor naught
Yet it is passing pleasing to the world.
He sees that the play will give him the opportunity he has been seeking to avenge his son's murder. Like Hieronymo, the protagonist in the poem has found his theme; what he is about to perform is not "fruitless."
After this repetition of what the thunder said comes the benediction:
Shantih Shantih Shantih
From: Nancy Gish <[log in to unmask]>
To: [log in to unmask]
Sent: Friday, September 9, 2011 7:41 PM
Subject: Re: 'The Waste Land' - a recitation (was Re: vis-a-vis 'Four Quartets')

That is an (not "the") interpretation of "Shantih."  But the lines above that are about violence, chaos, and murder. Moreover, Cleo Kearnes has pointed out that the full ending of the Upanishad starts with "Om," and Eliot omits it (though we know he studied them). 
So you are free to interpret one line as shaping all the rest, but that interpretation is not "what the lines say": it is one reading of very mixed lines.

>>> Chokh Raj 09/09/11 7:20 PM >>>
apropos TWL's ending
Peter Montgomery wrote: "They end it with a very positive tone, but then that's what the lines say."
A valuable observation, Peter. Thanks.

From: Peter Montgommery <[log in to unmask]>
To: [log in to unmask]
Sent: Friday, September 9, 2011 2:07 AM
Subject: Re: vis-a-vis 'Four Quartets'

Interesting to see that presentation again.
They end it with a very positive tone, but then that's what the lines say.
I suppose one could render them in an ironic way, but that would seem rather forced.


Quoting Chokh Raj <[log in to unmask]>:
> THE WASTE LAND - read by Edward Fox, Eileen Atkins, and Michael Gough