Page:Popular Science Monthly Volume 15.djvu/197

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determination from the water is maintained for the upper portion of the boat by a distribution of air-cases at the sides and ends, scientifically proportioned. The self-bailing characteristic is effected by a deck adjusted with reference to the draught of the boat, so that, whatever be the load of the latter, the deck is above the load-line; and, being

PSM V15 D197 Self righting life boat on its carriage.jpg
Fig. 3.—Self-Righting Life-Boat upon its Carriage.

fitted with tubes extending vertically down through the bottom of the boat, it follows that whatever water the boat takes on board falls through the tubes, in obedience to the law which. compels fluids to seek their level, and leaves the deck free. The delivery tubes are furnished with self-acting valves, opening to the downward pressure of the water shipped by the boat, and shutting to the pressure of the jets from below. Cork ballast adds by its weight to the stability of the boat, and augments its buoyancy in case the boat be stove. Two masts, made detachable, are provided, fitted with two low lug-sails and a jib. The boat is wellnigh invulnerable, but its great weight and draught, and the resistance its high bows offer to the wind, often make its towage by steam-tug necessary to enable it to reach a wreck at a distance. Particular attention is given to the stowage of its ropes, lines, anchors, and other articles carried in life-boats, these being arranged by a strict method with reference to economy of space and facility of use, and always kept on board, ready for service, lest any of them should be forgotten in the excitement of a sudden sum-