Poems backwards reading

This shouldn't work, and I keep expecting to hear ghostly phrases about Paul McCartney being dead, but I've discovered that some poems can be read backwards.

This happened one night when I was reading before bed, barely able to keep my eyes open, and sleepily started at the bottom of a page and worked my way up to the top of the poem. Maybe because I knew the poem well, its intrinsic sense remained. How could that be? Isn't language dependent on order? Not perhaps. Latin roots our language of dependent on order not (Yoda notwithstanding).

The above may be one of the oddest sentences I have ever written.

Nevertheless! With some poems, such as Tennyson's The Eagle, which seem to rely on an accumulation and sequence of events, it doesn't quite work:

Like a thunderbolt he falls.
He watches from his mountain walls
The wrinkled sea beneath him crawls

Ringed with the azure world, he stands.
Close to the sun in lonely lands.
He clasps the crag with crooked hands.

But with Yeats's shivery The Second Coming, something strange and awful remains:

And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?
now I know
That twenty centuries of stony sleep
Were vexed to nightmare by a rocking cradle,
The darkness drops again;
all about it
Reel shadows of the indignant desert birds.
somewhere in sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while
but
a vast image out of Spiritus Mundi
Troubles my sight

Surely the Second Coming is at hand.
Surely some revelation is at hand;
the worst
Are full of passionate intensity.
The best lack all conviction,
everywhere The ceremony of innocence is drowned;
The blood-dimmed tide is loosed
Mere anarchy is loosed upon the world,
Things fall apart; the centre cannot hold;
The falcon cannot hear the falconer;
Turning and turning in the widening gyre

It's a rough copy-and-paste job, but how is it that any sense of the emotive strength and imagery remain? Because I think they do. I'd be outraged if someone suggested reading in reverse something I've written, and this is utter bowdlerization of these fine pieces of art, but I offer them up, vivisection-like, from which to learn.

To learn what, I do not know. But I can't explain why this works so well.