They walked a distance back, and set the sledge in motion. Then out on the ice they spun, Chet cracking his long whip in true Esquimau fashion. The new ice cracked and groaned under their weight, and when they were in the middle of the lead it began to buckle. "Spread out--don't keep together!" yelled Barwell Dawson. "Chet, whip up the dogs and let 'em go it alone!" The boy understood, and gave the canines the lash. Away they sped at breakneck speed. Then Chet leaped to one side, and he and the others continued on their way a distance of fifty or more feet from each other. It was a great risk they had assumed, and each instant they thought the ice would break and let them down in the water. A rescue under such conditions,--with the thermometer standing at fifty-three degrees below zero,--would have been out of the question. "The ice is going down!" screamed Andy, just as he was within a rod of the north shore. "Hurry up!" There was no need to sound the warning, for all understood the peril only too well. They increased their speed, and slid the remaining few feet. Then, just behind them, they saw the ice buckle and break, allowing a stream of icy water to run over it. "Safe, and thank Heaven for it!" murmured Barwell Dawson, when he could catch his breath. "Don't ask me to take another such run," panted Professor Jeffer. "I thought we'd surely be drowned!" As soon as they had recovered somewhat from the dash, they walked on to where the dogs had stopped. In letting them go, Mr. Dawson had known that they were in no physical condition to run out of sight. When the travelers came up, they found the canines stretched out resting. The harness was in a snarl, and it took them the best part of a quarter of an hour to get the team straightened out again. "Did you notice that the ice looks purple?" remarked Andy, as they went on once again. "I did," answered Barwell Dawson. "It is as peculiar as it is beautiful." He had noticed the purple ice several days before, and also several mirages in the sky,--mirages that looked like hills and mountains, but which he knew were only optical delusions. Coming northward, the party had also had a splendid view of the _aurora borealis_, or Northern Lights, that mysterious glow thought to be electrical or magnetic. Once Andy had said that he could hear the lights, and that they sounded like the low hissing of steam. It grew colder that night, and it was all the explorers could do to keep from freezing. They had a small quantity of tea left--a quarter of a pound--and after melting some snow over their alcohol stove, drank the beverage boiling hot. Then they made themselves a hot stew of pemmican and ground-up peas. Each of the dogs received a chunk of frozen walrus meat, something they gnawed on savagely, so great was their hunger.