The next to do good work within this area was William Scoresby the elder, whose only equal as a whale-fisher was his son. To him we owe the invention of the crow's nest, that cylindrical frame covered with canvas, entrance to which is given by a trap-hatch in the base, reached by a Jacob's ladder from the topmast crosstrees, the conning-tower, so to speak, carried since by every ship on Arctic service. He was also the inventor of the ice-drill and many another implement and device used in Polar navigation; and he it was who sloped off his fore and main courses to come inboard to a boom fitted to the foot, used by every whaler, by which, in fact, you may know them. He also, long before the _America_, discovered the advantage of flat sails, and, in order to get his weights well down, he filled his casks with water as ballast and packed them with shingle, so that, instead of going out light, he was in the best of trim, with a power of beating to windward that took him to the fishing ground in double quick time and further into the ice, when he chose, than any of his competitors. [Illustration: WHALERS AMONG ICEBERGS] Out in the _Resolution_ in 1806 he saw from his crow's nest, in which he often spent a dozen hours at a stretch, that below the ice-blink—the white line in the sky which betokens the presence of ice—there was a blue-grey streak denoting open water, and that the motion of the sea around the ship must be due to a swell, which could only come from open water to the northward. On the 13th of May he started for this. By sawing the ice, hammering at it, dropping his boats on to it from the bow, sallying the ship—that is, rolling her by running the crew backwards and forwards across her deck—and, in fact, using every means he could think of, he passed the barrier in the eightieth parallel, and, on the 24th of June, attained 81° 30´, the farthest north ever reached by a sailing vessel in these seas. On that day there was not a ship within three hundred and fifty miles of the _Resolution_. The bold venture proved a thorough success; in thirty-two days he filled up with twenty-four whales, two seals, two walruses, and a narwhal—one of the most profitable of his thirty voyages.