On the 15th they reached Nulato, six hundred miles from the mouth, where they spent the winter. Here they found a curious method of fishing practised all through the season. Early in the winter large piles or stakes had been driven down into the bed of the river, and to these were affixed wickerwork traps like eel-pots on a large scale, oblong holes being kept open over them by frequently breaking the ice. This was cold work, for the temperature ran low. "In November and December," says Whymper, "I succeeded in making sketches of the fort and neighbourhood when the temperature was as low as thirty degrees below zero. It was done, it need not be said, with difficulty, and often by instalments. Between every five strokes of the pencil, I ran about to exercise myself or went into our quarters for warmth. The use of water-colours was of course impracticable—except when I could keep a pot of warm water on a small fire by my side—a thing done by me on two or three occasions, when engaged at a distance from the post. Even inside the house the spaces near the windows, as well as the floor, were often below freezing point. Once, forgetful of the fact, I mixed some colours up with water that had just stood near the oven, and wetting a small brush commenced to apply it to my drawing block. Before it reached the paper it was covered with a skin of ice, and simply scratched the surface, and I had to give up for the time being." On the 12th of May the Nulato River broke up and ran out on the top of the Yukon ice for more than a mile upstream; and in a few days the ice of the main river was coming down in a steady flow at a rate of five or six knots, surging into mountains as it met with obstacles, and grinding and crashing and carrying all before it, whole trees and banks being swept away on its victorious march, the water rising fourteen feet above the winter level. On the 26th Whymper and Dall started with two Indians and a steersman in a skin canoe, the river still full of ice, and navigation difficult. They had proceeded but a short distance when they came to bends, round which logs and ice were sweeping at a great rate, so that it was necessary for a man to stand in the bows of the canoe, with a pole shod at one end with iron, to push away the masses of ice and tangle of driftwood. They could often feel the ice and logs rolling and scraping under the canoe; and it was not the thickness of a plank between them and destruction, but that of a piece of sealskin a tenth of an inch thick.