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lapped timber construction, as shown in the section in Fig. 3, and are to be made extra strong for load transmission, as the thorough cross-bracing will indicate. They are to be made watertight so that they can be pumped dry, to the chamber Ratchet Nut 4 -- : if S&S : -- Mh, = ----- Big 4 DrrAiw- or CAP at Tor or A- FRAME SHOWING Screw DEVICE. ceiling, but they are to be filled with ~ water at the beginning of the operation, for reasons explained below. The cais- sons are built with the outer cutting edge higher than the inside to keep the escaping compressed air away from the vessel, which would otherwise be dis- turbed and further sunk in the mud. As the bottom of the wreck is about 10 ft. below the present harbor bottom, the caissons will be sunk some 10 ft. farther so as to make certain that their bottoms are well below the lowest part of the sunken frame work. When the cais- sons are driven to their required depth, the dock is to be continued straight across their tops up to the side of the wreck and is to be used as the working platform, from which to conduct all op- erations. On the outside face of the caissons toward the wreck there will be hung in vertical lines and spaced about every 4 ft. longitudinally, a number of wire cables stapled lightly to the wooden framing of the caisson and coiled at the upper end on the caisson top, with the lower end passing, under the driving edge of the caisson and: coiled in the working chamber. On one side, there are to be 34-in. steel cables, such as are erdinarily used in construction work, and N\ TAE MARINE REVIEW on the other they are to be at least of 2-in. plough steel with an ultimate Ioading capacity of 400,000 Ibs. We can now imagine the caissons sunk to their proper elevation. At every 4 ft. along the inner face of the left hand set (Fig. 2) is a 3%4-in. cable coiled on top of the dock, passing down the side of the caisson, under its cutting edge into the working chamber, where it hangs coiled. On the right-hand set of caissons hang 2-in. cables arranged in the same manner. Now in the opening below the working chamber below the left-hand caisson,- a 3-in. wrought iron, inside-coupled pipe is driven out into the mud, which will stand against the air pressure from the chamber, toward the opposite or right-hand caisson. Grad- ually, section by section this pipe is driven over until it penetrates the work- ing chamber of the opposite caisson. Into this pipe is then led the end of the 34-in. cable coiled in the left-hand working chamber, as a pilot cable which is to connect the two working chambers. Now, from the right-hand caisson the 3-in. pipe is drawn in, section after sec- tion removed and slipped over the con- necting cable, until finally the whole pipe is taken in and the two chambers are connected only by cable through the intervening mud. Now, the end of the 34-in. cable in the right-hand chamber is spliced to the 2-in. cable hanging there and, by ten- sion applied at the upper end of the 34-in. cable at the top of the left-hand Fig. 3 and in detail in Fig. 4. Section A-B. September, 1910 through the soft mud up tight against the bottom of the wreck. Pulling is continued until the 2-in. cable appears cn the left-hand dock and _ has thus passed completely under the ship. This process is repeated for each of the cables, spaced every 4 ft., until finally there would be about 60 of these cables passing under the ship, snug up against its bottom and held securely on the solid dock on either side. There now remains to design some method of tackle whereby these cables may be simultaneously tightened and raised, bringing, as they must if they are raised, the hulk up from the muddy bottom with them. The tackle, as now designed, is shown on the section in It con- sists primarily of an A-frame above each of the cables, with the main mast footing on the inside wall of the cais- son and with the bracing leg and the guy ropes carrying back to the dock proper. At the top of each frame is a cast iron cap, such as is shown in the detail design in Fig. 4, carrying a pack- screw system, by means of which the lifting is to be done. The jack-screws are designed to lift more than 100 tons and the bottom end is formed of an eye-bar like that 'cf a bridge truss, while the clamp which erips the cable ends in two similar eye- bars into which the screw is fastened with @ 334-in. steel pin (Fig. 6). . This screw passes up through the cast iron cap and is provided with a ratchet-head- ed nut, by means of which the screw is operated. In order to provide uni- versal motion to care for the necessary movement in the cable and also to pre- vent the cable from twisting during its raising, a special saddle or head has been designed for the cap. Primarily this consists of an oval cup-shaped in- dentation in the upper face of the cap into which fits a similarly shaped saddle, provided with a 3-9/16-in. opening, A SS SS © \ O © ENG.NEWS. Eo ee ye B Section C-D.--- Fic, §--Detratts oF UNIversAL Jotnt Cap. caisson, the: two cables are gradually pulled up toward the bottom of the ship. First the bights around the driving edges are pulled out, then the light staples holding the cables to the caisson faces, and then the cable is pulled through which the 314-in. screw passes and provided further with a flat side against which the flattened side of the lifting screw sets. The oval-shaped opening allows universal motion without twisting in a horizontal plane and the pra e Rt? Te