Gandalf and the Ring...

[Dúnedain]

I've always found it strange how Gandalf tells Frodo has a great suspicion about the ring and fears touching it. Then he does touch it and isn't affected by it. Then he realizes it is in fact the One Ring and yells at Frodo to not tempt him with it. I'm going to post the two passages below, let's try and make some sense out of them

The Fellowship of the Ring: The Shadow of the Past

Frodo took it from his breeches-pocket, where it was clasped to a chain that hung from his belt. He unfastened it and handed it slowly to the wizard. It felt suddenly very heavy, as if either it or Frodo himself was in some way reluctant for Gandalf to touch it.

Gandalf held it up. It looked to be made of pure and solid gold. 'Can you see any markings on it?' he asked.

'No,' said Frodo. 'There are none. It is quite plain, and it never shows a scratch or sign of wear.'

'Well then, look!' To Frodo's astonishment and distress the wizard threw it suddenly into the middle of a glowing corner of the fire. Frodo gave a cry and groped for the tongs; but Gandalf held him back.

'Wait!' he said in a commanding voice, giving Frodo a quick look from under his bristling brows.

No apparent change came over the ring. After a while Gandalf got up, close the shutters outside the window, and drew the curtains. The room became dark and silent, though the clack of Sam's shears, now nearer to the windows, could still be heard faintly from the garden. For a moment the wizard stood looking at the fire; then he stopped and removed the ring to the hearth with the tongs, and at once picked it up. Frodo gasped.

'It is quite cool,' said Gandalf. 'Take it!' Frodo received it on his shrinking palm: it seemed to have become thicker and heavier than ever.

Now with that section, Gandalf touches it at least once, attached to a chain or not, it is still touched, unless of course the chain intercedes the feeling of it's power, which wouldn't make much sense. The text is vague when he uses the tongs to take it from the fire. He may have used his hands, and that is why Frodo gasps thinking it would have burned Gandalf, though he could used the tongs and Frodo only gasps at seeing it again. Either way, he touches it at least once.

Moving on:

The Fellowship of the Ring: The Shadow of the Past

'But I have so little of any of these things! You are wise and powerful. Will you not take the Ring?'

'No!' cried Gandalf, sprining to his feet. 'With that power I should have power too great and terrible. And over me the Ring would gain a power still greater and more deadly.' His eyes flashed and his face was lit as by a fire within. 'Do not tempt me! For I do not wish to become like the Dark Lord himself. Yet the way of the Ring to my heart is by pity, pity for weakness and the desire of strength to do good. Do not tempt me! I dare not take it, not even to keep it safe, unused. The wish to wield it would be too great for my strength. I shall have such need of it. Great perils lie before me.'

It is like a complete reversal. Why was he not affected? And why was he not tempted when the Ring was given to him, whether it be on a chain or not?