Having taken on board all the stores that the _Valorous_ carried, as well as a full supply of coal, the _Alert_ and the _Discovery_ started in company for the North. The advantages of steam navigation were made even more apparent as they proceeded, for the ships were able to steam through ice-encumbered water which would have been quite impassable for sailing vessels. Depending so much upon the wind, a sailing vessel is only able to make headway amongst heavy drifting floes by means of long hawsers, run out and made fast to a mass of ice and then slowly hauled in at the capstan. Steamers, on the other hand, experience no difficulty in forcing their way past and between the lesser floes, and Sir George Nares, who had had a great deal of experience of sailing vessels in the ice regions, was frequently astounded at the ease with which the two steamers rammed their way, clearing from out of their course lumps of ice which would have been difficult obstacles to a sailing ship. Those on board, however, were not to escape without some experience of the peculiarities of ice movements. The vessels were going to make fast for the night, and a boat's crew was sent from the _Alert_ to carry an anchor to a large, heavy mass not far distant. On near approach it was seen that the lump was very rotten, and, as no hold for the anchor could be found near the water-line, one of the men volunteered to clamber up to the top and, with an ice chisel, make a hold for it. He clambered on to the slippery, treacherous mass, and, after a great deal of very careful exertion, succeeded in reaching a point high enough for his purpose. He began lustily to drive in the chisel, but so rotten was the ice, that instead of merely chipping out a crevice, he cracked the top of the lump. Another blow, and, to his intense amazement, a huge mass in front of him slid away. Gliding down the side, fortunately away from the boat, it splashed into the sea. But the removal of so much from the top of the berg upset its balance, with the result that it swayed from one side to the other as it recovered its equilibrium. The unfortunate sailor, with nothing to cling to, had to scramble up and over the summit as the berg dipped down; but no sooner was he over the top than the berg swung the other way, and he had to scramble back again. There was no means of escape until the berg settled down once more, and in the meantime his companions in the boat and on the steamer were shouting with laughter at the antics of what they called their squirrel on the iceberg.