Neither, however, became so absorbed in his studies as to become reconciled to his enforced residence above the seven spruces. Day after day they ventured out and up and down the canon, or up the side of the mountain on the side of which their shack was located, but no discoveries resulted. The absence of snow-shoes made travel impossible except on top of a strong crust, and even then a realization of a constantly increasing danger resulted in making such trips shorter and shorter. The danger was this: blizzard succeeded blizzard until the willows, ten feet tall, which grew thickly in the canon, were completely concealed, also the scrub hemlocks and quaking asp on the mountainside. The tops of the bushes, lashed by the wind until they became finally snow covered, formed each a dangerous hollow under a crust thinner and weaker than the surrounding surface. This painful discovery was made by Leslie. One bright day, leaving Ross to cut off the branches of a tree that he had felled for fire-wood, Leslie took the gun and started down the canon on a tour of exploration. "The crust is stout enough to hold up an ox, Doc," he declared, bringing the butt of the gun down on it hard, "and I'm going out to see what there is to see--and shoot." "Shoot!" echoed Ross, poising the axe in air. "I'd like to see something shootable up here beside coyotes, and we never see them--only hear 'em!" and the axe descended with a thud. Leslie laughed, shouldered the gun and tramped briskly down the canon, while Ross wielded the axe and, whistling cheerfully, thought of the progress he was making in his studies. Presently, he rested on his axe handle and chafed his cheeks and nose briskly with the shaggy mittens he had found in the box of clothing left in the shack. "I don't want any more frost bites in mine!" he muttered. He had had several experiences of the kind that winter, the altitude being so great that he did not realize the intense cold until nose or cheek or ear had become frost nipped. He was resuming his axe when a faint sound traveled up the canon on the wings of a slow south wind. Ross straightened himself and listened. Again came the wind and the sound. With the axe in his hand he slipped and slid down the mountainside until he stood in the canon below the seven spruce trees. There he paused long enough to distinguish in the sound the faint muffled cry, "Ross!" and "Help!" "Coming!" yelled Ross frantically. "Where are you?" He did not await a reply but, slipping unsteadily along the icy crust, he hurried down the canon in the general direction of Leslie's voice, yelling intermittently, "Coming--here I am! Where are you, Less?" As he came to the cliff over which he had been lowered into the canon, he heard Leslie's voice again, still curiously muffled, although evidently only a little way in advance. It seemed to rise from beneath the ground. "Hold on, Ross. Don't come fast. I've fallen through among the willows."