Jack and Mark, however, found time to help the whalemen secure the oil from the carcasses of the stranded leviathans which surrounded the _Orion_. They, with old Andy and Phineas Roebach, began to go out with the parties of blubber-hunters to guard them at their work. For now great troops of polar bears appeared from the north, evidently making their way from the fields of ice that likewise had become stranded on the old sea bed; and these white bears were as savage and as hungry as were the Kodiak bears that infested the river. The two chums, thus engaged, had an adventure one day that they were never likely to forget. Seeing that there were several of the huge walruses imprisoned in the lakes of salt water remaining in the ocean bed, Jack and Mark desired to kill one for its great tusks. They knew where there was one of the beasts--half as heavy as an elephant--and not far from one of the last whales the crew of the _Orion_ were cutting up. The boys were guarding this special party of seamen at their work, but had seen no bears since sunset. There was plenty of light, for both the earth-planet was shining on them and her moon likewise, although the latter was now in her last quarter. Quite sure that the sailors would not be molested, Jack and Mark crept away toward the pool where they had seen the walrus. They soon found, however, that they were not alone. Washington White had come over from the bark, and seeing what the boys were about he followed them. "Is you suah 'nuff gwine ter try an' shoot dat hugeous wallingrust, an' pull his teef?" he whispered. "Yo' boys will git killed, some day, foolin' wid sech critters." "You'd better go back, then," said Mark, "if you are afraid." But the darkey wanted to see how the boys proposed to go about the work of capturing the walrus. Jack had prepared a long and stout line with a whale lance at one end and a sharp spike at the other. The boys very well knew that the bullets from their rifles would make little impression on the walrus. They had to go about his, capture in a different way from shooting bears. The salt water lake in which the walrus was trapped was perhaps a mile across, and there were several blow-holes in it. The party had to lie down behind a barrier of seaweed that the wind had tossed up in a great windrow, and wait for the walrus to appear at one hole or another. When his fierce head came into view Jack and Mark, with their satellite, Washington, crept around to the rear of the creature, and then made a swift but careful advance upon his position. They reached a spot upon the ice not more than ten yards from the blow-hole without attracting the attention of the walrus. Instantly Jack motioned his chum to stand ready to drive the steel spur at the end of the line into the ice to hold the beast, while he went forward with the harpoon. Right at the edge of the broken ice, within ten feet of the monster, Jack Darrow stood a moment with the weapon poised.