Don't you think Denethor revealed the position of the Ring to Sauron? a plot
hole?
No, I don't think he did. I think he used the Stone on his own and saw
Frodo in the tower; I don't think Sauron showed Frodo to him or knew that he
had been looking at Cirith Ungol. Also, the palantír does not allow
Sauron to read minds. Unfinished Tales tells how two people using
Stones in accord with each other could converse:
"Looking one at the other, they would exchange 'thought'--not their full or
true thought, or their intentions, but 'silent speech,' the thoughts they
wished to transmit...." (p. 415)
UT also says that Sauron did not have his own palantír connection open at all
times:
"It must also be considered that the Stones were only a small item of Sauron's
vast designs and operations ... he would not (and could not) have the
Ithil-stone under perpetual observation." (p. 407)
Why didn't Gandalf try to hide the Palantir, knowing now that on the other
side there's Sauron?
Two thoughts on this question: First, UT says that Gandalf's main concern
was whether Denethor, like Saruman, had gone over to Sauron's side. When
he saw that had not happened, he may have concluded that Denethor had not been
using the palantír after all. Second, I'm not sure that Gandalf would
have been able to get at the palantír of Minas Tirith. I"m willing to bet
that it was kept in a locked room, and that Denethor had the only
key.
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LOTR fanfiction by me and a friend
"Debbie Does The Two Towers," COMPLETE! Chapter 18: Debbie the Red reaches Isengard, Aragorn has Evenstar envy, and Debbie the Black sings!