In laying his plans Parker had proceeded upon the assumption that, once the cold had gripped the glaciers, they would remain motionless until spring. All available evidence went to prove the correctness of this supposition, but Alaska is a land of surprises, of contrasts, of contradictions: study of its phenomena is too recent to make practicable the laying down of hard and fast rules. In the midst of a season of cruelly low temperatures there came a thaw, unprecedented, inexplicable. A tremendous warm breath from the Pacific rolled northward, bathing the frozen plains and mountain ranges. Blizzards turned to rains and weeping fogs, the dry and shifting snow-fields melted, water ran in the courses. Winter loosed its hold; its mantle slipped. Nothing like this had ever been known or imagined. It was impossible! It was as if the unhallowed region were bent upon living up to its evil reputation. In a short time the loosened waters that trickled through the sleeping ice-fields greased the foundations upon which they lay. Jackson Glacier roused itself, then began to glide forward like a ship upon its ways. First there came the usual premonitory explosions--the sound of subterranean blasts as the ice cracked, gave way, and shifted to the weight above; echoes filled the sodden valley with memories of the summer months. It was as if the seasons had changed, as if the zodiacal procession had been thrown into confusion. The frozen surface of the Salmon was inundated; water four feet deep in some places ran over it. The general wonder at this occurrence changed to consternation when it was seen that the glacier acted like a battering-ram of stupendous size, buckling the river ice in front of it as if ice were made of paper. That seven-foot armor was crushed, broken into a thousand fragments, which threatened to choke the stream. A half-mile below the bridge site the Salmon was pinched as if between two jaws; its smooth surface was rapidly turned into an indescribable jumble of up-ended cakes. When a fortnight had passed O'Neil began to fear that this movement would go on until the channel had been closed as by a huge sliding door. In that case the rising waters would quickly wipe out all traces of his work. Such a crumpling and shifting of the ice had never occurred before--at least, not within fifty years, as the alder and cottonwood growth on the east bank showed; but nothing seemed impossible, no prank too grimly grotesque for Nature to play in this solitude. O'Neil felt that his own ingenuity was quite unequal to the task of combating this peril. Set against forces so tremendous and arbitrary human invention seemed dwarfed to a pitiable insignificance.