Byzantium

Hi, I would be very grateful if you could help me identify
the poem "Byzantium."
I am reading a small book and it says:

Here now are the closing lines of Yeats's poem "Byzantium":
----poem----
Marbles of the dancing floor
Break bitter furies of complexity,
Those images that yet
Fresh images beget,
That dolphin-torn, that gong-tormented sea.
-------------

As I know, Yeats has the poem named "Sailing to Byzantium."
I read it, but its closing lines are totally different from the one above.

(1) Did Yeats write the poem "Byzantium"?
(2) If not, whose poem is the one above?

I would appreciate it if any of you could help me.
Thank you.

There are two Yeats poems on the subject of Byzantium: Sailing to Byzantium" and "Byzantium." Check out the Google search: http://www.google.com/search?hl=en&q...=Google+Search

Virgil, thank you very much for your help.
I should have checked the Google search.
Thank you again.