A ship is exposed to considerable danger when she finds herself among icebergs in a calm; but since these are over-spread by a dazzling sheen, even in the thickest mist, the peril of the position is to be avoided at the last moment by warping. 15. As the happy choice of a sea-way is one of the essential conditions of success in ice-navigation, the ability to determine the ship’s position and to ascertain whether a surface covered with ice to the horizon, admits of being penetrated, is most desirable. Hence the employment of a balloon would be of the last importance in Arctic navigation. The advantage of being able to ascend from the ship in a balloon secured by a rope, to the height of a few hundred feet, is self-evident; and, undoubtedly, the first vessel which avails herself of this great resource will derive extraordinary benefit from it. 16. From the deck of a ship even drift-ice appears to be of such solidity at a little distance as to defy navigation, while from the mast-head more water than ice may be descried. In order then to extend the horizon, a look-out, called “the crow’s nest,” is fixed on the mast-head, in which an officer is always on the watch, and from which all the operations of the vessel are directed. In a ship of the size and height of the _Tegetthoff_ the horizon visible from “the crow’s nest” extends to about eleven miles,[8] but at the distance of even five miles the possibility of penetrating cannot be determined with sufficient exactness. It is the business of the officer in “the crow’s nest” to observe the passages through the ice and distant objects generally, as he is in the best position to fulfil this most important duty. It is the special business of the watch on the forecastle to mark what lies in the immediate neighbourhood of the vessel, and his constant care is demanded to avoid isolated ice-floes and prevent collision with them. The seaman at the helm steers the ship by the signs and calls which come to him from “the crow’s nest,” and modifies them according to those of the watch on the forecastle. The rest of the crew remove the smaller fragments of ice from the vessel’s course, special care being taken to prevent their damaging the screw.