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c : : 3 : E VOL. 39. CLEVELAND, MARCH 25, 1909. NEW YORK No. 12 Dry Dock at Pearl Harbor. The dry dock at the naval station, Pearl. harbor, Hawaii, is to be the largest ever constructed by the navy department. Its: overall... length... is 1,195 ft., whereas the longest dock pre- viously constructed is at Philadelphia, 799 ft. overall. The Puget Sound dry dock recently contracted for is 863 ft. overall. An innovation, so far as American docks are concerned, is that there will be four caisson seats, two as usual at the entrance to the dry dock and two others near the middle of the dock, dividing the main structure into an inner and outer dock. There will be two steel caisson gates and the arrangements will be such that with a ship in the inner dock the outer dock may be filled and emptied inde- pendently, thus allowing the ship upon which the most extensive re- pairs are to be made to remain in 'the inner dock while ships with minor fitted be ee oree 4116340 Overall == ===116040"lo Outer Sill (Shae | repairs are being docked in. rapid succession 'in the outer. dock... By floating the 'inner caisson from the dry dock, ships of greater. length than any now in existence or planned could be docked. A 'trapezoidal form of head has been designed for this dock different from any hitherto considered. It is so arranged that three destroyers may be docked side by side extending to the very head of the dock, leaving room for three. other. small craft in the inner dock. Bids will also be received for the usual forms of V- shaped head and arched head, _ The draught over sill at mean high water will be 35 ft., which is' more than any other dock excepting the one at Puget Sound where the great variation in tides required a draught of 38. ft: -' The: conditions of: tide | at Pearl harbor are such that the larg- est battleship may enter the dock at yee AO te ag ee = -O6F = ale 68S any stage of the tide. Concrete will be used throughout in the walls and floor Granite lining will be used only at caisson seats and the coping at entrance and mnfaterial slides. The conditions for the use of concrete are believed to be more favorable at Pearl harbor than at any point in the United . States on account of the equable climate and absence of frost. A marked improvement over all previous docks has been developed in connection with the dock for Pearl harbor, in that the working floor will be absolutely level from end to end, giving a level working sur- face, free from the usual obstructions, such as_ bilge-block slides, docking keel block bearers, bilge block chains, temporary electric wires, temporary compressed air lines, etc. The at- tempt has been made many times pre- viously to accomplish this object but never with success. It has been ac- a | eet 0, | = 2 3 NY, (eg et Pee ai ins tgp hers ete meron oar TYPE SECTION TYPE.SECTION THRO'BODY THRO MATERIAL Or DOCK LIOE i wore -- = Se eee ELEVATION OF ENTRANCE Discharge Culvert. 4 Crane Track C ee -=100----- 4 PEARL HARBOR,