The crow's nest is an apparatus placed on the main-top-mast, or top-gallant-mast head, as a watch tower for the officer on the lookout. It is closely defended from the wind and cold, and is furnished with a speaking trumpet, a telescope and rifle. The most favorable opportunity for prosecuting the fishery in the Greenland seas, commonly occurs with north, north-west or west winds. At such times the sea is smooth, and the atmosphere, though cloudy and dark, is generally free from fog and snow. The fishers prefer a cloudy to a clear sky; because in very bright weather, the sea becomes illuminated, and the shadows of the whale-boats are so deeply impressed in the water by the beams of the sun that the whales are apt to take the alarm. Fogs are only so far unfavorable as being liable to endanger the boats by shutting out the sight of the ship.--A well constructed whale-boat floats lightly and safely on the water,--is capable of being rowed with great speed, and readily turned round,--it is of such capacity that it carries six or seven men, seven or eight hundred weight of whale-lines, and various other materials, and yet retains the necessary properties of safety and speed. Whale-boats being very liable to receive damage, both from whales and ice, are always carver-built,--a structure which is easily repaired. The instruments of general use in the capture of the whale, are the harpoon and lance. There is, moreover, a kind of harpoon which is shot from a gun, but being difficult to adjust, it is seldom used. Each boat is likewise furnished with a "jack" or flag fastened to a pole, intended to be displayed as a signal whenever a whale is harpooned. The crew of a whale-ship are separated in divisions, equal in number to the number of the boats. Each division, consisting of a harpooner, a boat-steerer, and a line-manager, together with three or four rowers, constitutes a "boats crew."