About an hour before noon
The sky was cloudy , threatening rain . The walls , now smooth , now broken by pinnacles and shoulders , were sad and gray in color . Milton sometimes slept uneasily , but for the most part he lay with lips compressed , eyes on the gliding cliffs . About an hour before noon , the familiar warning roar of rapids reached their ears . Rounding a curve , carefully , they snubbed the Ida to a rock while Agnew clambered ashore for an observation . Just below them a black wall appeared to cut at right angles across the river bed . The river sweeping round the curve which the Ida had just compassed , rushed like the waters of a mill race against the unexpected obstacle and waves ten to twenty feet high told of the force of the meeting .