in a ship, are made of the common sail-cloth, and are usually between twenty-five and thirty feet long, according to the size of the ship, and are of the form of a cone ending obliquely: when they are made use of, they are hoisted by ropes to about two thirds or more of their height, with their basis defended circularly by hoops, and their apex hanging downwards in the hatchways of the ship; above each of these, one of the common sails is so disposed, that the greatest part of the air rushing against it, is directed into the wind-fall, and conveyed, as through a funnel, into the upper parts of the body of the ship.