Well, simply put, the first sentence concerns itself with the shadow about it (it being the
Balrog). Now this shadow, reaching out 'like two vast wings' is taken by some to be a simile. I'm fine with that, whilst still suggesting that the perfect thing to cast a wing-like shadow would be wings, but let's not quibble (though I'm not at all averse to a good old quibble).
For clarity: what's your idea of the shadow before the spread "like wings" statement? Especially considering your
"cast" a wing-like shadow here
For example, when the Balrog came to the edge of the fire the
"light faded as if a cloud had bent over it." Then we have a dark figure steaming with fire racing toward the company, but when
Boromir sounded his horn, for a moment
"the fiery shadow halted"
There's no spreading yet. Okay, then the shadow about it reaches out like two
vast wings. It had vast wings, or "potentially" vast wing, the whole time? And still again, the fire in it seemed to die, but the
"darkness" grew, and then it reaches up to a great height and its "wings" (as easily understood as its shadow as are the wings understood as "sails" in Tal-Emar", see below for a fuller version) spread from wall to wall.
And when it falls, the Balrog fell forward and
"its shadow plunged down and vanished."
Again, I'm just wondering about you interpretation considering other statements in the passage.
And indeed, as noted, when the "new"
Balrogs emerge in the later Silmarillion, we have:
" . . . their hearts were of fire, but they were cloaked in darkness, and terror went before them; they had whips of flame. Balrogs they were named." JRRT, The Later
Quenta Silmarillion
I know this wasn't published in
The Hobbit, The Lord of The Rings, The Adventures of Tom Bombadil and The Road Goes Ever On, but it still hooks in perfectly with the simile reading.
Now I'm not saying that there can't be a connection between two such disparate sentences, I'm saying there doesn't have to be, and I just think the simplest explanation fits best - real wings.
You've granted that we
can have a simile here, and the general meaning of simile is:
a figure of speech that compares two unlike things with "like" or "as."
Writers use 'em all the time. Readers recognize 'em all the time. Similes are
like acorns on oaks!
Or something else
Again, the flight from
Thangorodrim using real wings is the simplest explanation - you don't need simile to actual words,
back to simile etc - we can just take
Tolkien as writing exactly what he meant.
Both passages are simple enough to my mind.
Moria passage: simile to "word understood in light of simile" --
Durin's Folk passage: flying for fleeing.
And both passages are exampled not only in "writing in general" but in Tolkien's writing.
Inescapable logic really.
Well, as the Balrog escaped Thangorodrim. . .
"Greater than great houses are the ships of the Go-hilleg, and they bear store of men and goods, and yet are wafted by the winds; for the Sea-men spread great cloths like wings to catch the airs, and bind them to tall poles like trees of the forest. Thus they will come to the shore, where there is shelter, or as nigh as they may; and then they will send forth smaller boats laden with goods, and strange things both beautiful and useful such as our folk covet. These they will sell to us for small price, or give as gifts, feigning friendship, and pity for our need; and they will dwell a while, and spy out the land and the numbers of the folk, and then go. And if they do not return, men should be thankful. For if they come again it is in another guise. In greater numbers they come then: two ships or more together, stuffed with Men and not goods, and ever one of the accursed ships hath black wings. For that is the Ship of the Dark, and in it they bear away evil booty, captives packed like beasts, the fairest women and children, or young men unblemished, and that is their end. Some say they are eaten for meat; and others that they are slain with torment on the black stones in the worship of the Dark. Both maybe are true. The foul wings of the Sea-men have not been seen in these waters for many a year. . ." A Certain Author
To me there's nothing complicated here.
And reading the Moria encounter in the same (
un)light. . .