"Frodo seemed to be weary, weary to the point of exhaustion. He said nothing, indeed he hardly spoke at all; and he did not complain, but he walked like one who carries a load, the weight of which is ever increasing; and he dragged along, slower and slower, so that Sam had often to beg Gollum to wait and not to leave their master behind.
In fact with every step towards the gates of Mordor Frodo felt the Ring on its chain about his neck grow more burdensome. He was now beginning to feel it as an actual weight dragging him earthwards. But far more he was troubled by the Eye; so he called it to himself. It was that more than the drag of the Ring that made him cower and stoop as he walked. The Eye; that horrible growing sense of a hostile will that strove with great power to pierce all shadows of cloud, and gaze naked, immovable. So thin, so frail and thin, the veils were become that still warded it off. Frodo knew just where the present habitation and heart of that will now was; as certainly as a man can tell the direction of the sun with his eyes shut. He was facing it, and its potency beat upon his brow."