It was a bitterly cold day, for the southern winter had already set in in all its severity. The sea to the north of the island was comparatively smooth, but swept every now and then with violent gusts of wind from the southward. The sky was entirely covered by thick masses of cold grey cloud, every now and then torn up into great rolling masses by the sudden blasts of icy wind from the pole, which drove fierce storms of hard frozen snow across the bare and desolate island. But the roughness of the elements was a matter of small concern to the crews of the air-ships and the submarine cruisers, for both were independent alike of sea and storm. The former could literally ride upon the wings of the fiercest gale that ever blew. Their interiors were warm and wind-proof, and their machinery was powerful enough to drive them four and five times as fast as the air-currents in which they floated, while the latter had only to sink a few feet below the level of the waves to find perfect calm. The days, in short, were past when men had been at the mercy of the elements, and so the atmospheric conditions which would have made a modern naval attack upon a rocky and exposed coast almost impossible were not even taken into account in preparing to meet the threatened assault on Kerguelen Island. No one knew when or how the first assault would be delivered. All that was known was that, unless Olga and her advisers had completely altered their plans, the attack would take place either that day or the next, and consequently ceaseless vigilance was necessary on sea and land and in the air. In accordance with the plan arranged on board the _Narwhal_, ten air-ships rose above the clouds to an altitude of five thousand feet, and from each of these an electric thread hung down to as many signal-stations on the island, all of which were connected with the headquarters at the top of Christmas Harbour. Twenty cruisers patrolled the coast at a distance of a mile from the land, and two miles outside these the _Narwhal_ ran to and fro along the northern shore. All the more important inlets which had sufficient depth of water for submarine attack were guarded with mines and chains of torpedoes, so disposed that no vessel could possibly enter without firing them, and so giving warning of the locality of the attack. The afternoon passed without any alarm, and at nightfall the clouds sent down a blinding storm of snow, which, added to the intense darkness, made vision impossible both on land and sea, although high above the clouds the ten air-ships floated in a calm, clear atmosphere, under the brilliant constellations of the southern hemisphere.