The other responders have observed that Tolkien’s version requires that
“fire” be pronounced with a single syllable, but there’s nothing unusual
about that. Tennyson, for example, does it more often than not, and so
does Shakespeare.
Your version, on the other hand, is hideous, and doesn’t scan at all
unless you pronounce "ashes" as one syllable and “fire” as two. Don’t
quit your day job.
--
John W. Kennedy
"The blind rulers of Logres
Nourished the land on a fallacy of rational virtue."
-- Charles Williams. "Taliessin through Logres: Prelude"