In all this solid wall there was but one break. Not far from where Glen swam, and just beyond the snow-field, a narrow cleft appeared; and from it came an indistinct roar of waters. Glen felt himself growing numbed and powerless. He must either give up at once, and tamely allow himself to sink where he was, or he must swim to that cleft, and take his chances of getting out through it. He fully expected to find a waterfall just beyond the gloomy portal, and he clearly realized what his fate would be if it were there. But whatever he did must be done quickly. He knew that, and began to swim towards the cleft.