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34 THE MarINE. REVIEW THE NEW MITSU BISHI DRY DOCK AT NAGASAKI. The recent completion of the new dry dock of the Mitsu Bishi Co., at Nagasaki, gives to that port what will doubtless be the largest dry dock in the east for some time to come. {t has a total length on the coping, from the outer abutment to the head, of 722 ft. and a width across the body of 121% ft. The depth of the floor below the coping is 39 ft. at the center and 36 ft. at the sides, and there is 34 ft. of water on the sill at extreme high water. Ordinary merchant vessels can be docked at any stage of the tide while the largest ships, such as the 22,coo-ton Minnesota, can be docked at high tide without difficulty. The company was probably influenced somewhat in its decision to construct such a large dock by the fact that the previous absence of the facilities it affords has doubtless tended to limit the size of vessels in the Japanese trade and thereby had a restricting effect on its ship building industry. The new dock is, therefore, commercially as well -as technically of much importance. The entrance was built in deep water, but the head was cut in a rocky bluff. The foundation is of andesite rock, and the concrete sub-founda- tion'and cut-stone paving were laid directly on this firm base. Pile foundation was resorted to only for the right-hand wing wall, where the rock stratum slopes down deep into the water. The temporary dam for excluding sea water from the dock site had a top width of 12 ft. and slopes of 1:1% with a puddle core. The clay puddle enclosed between two rows of sheet-piles was 20 ft. in thickness for the lower part, but was reduced to 12 ft. near the top. The ground for the dam was prepared first by dredging the silt with a Priestman's dredger; a narrow trench was cut in the rock under water to receive the main piles for fixing the sheet-piles. When the main piles were set in position, they were fixed in the ground by filling the trench with con- crete. To prevent the percolation of water at the junction between the base of the dam and the -natural ground, as well as to take precaution against the sliding of the dam, a concrete mound about 5 ft. high was built under water, along the inside row of the main piles. After removing the silt layer, the depth of water near the middle of the dam was found to be more than 50 ft. at high tide, so that great care was taken in building this dam under water to make the puddle clay impervious at this great depth and correspond- ingly great water pressure. Fortunately, the execution of the work proved satisfactory, after pumping out the water. The side cut and excavated materials was 256,000 cu. yd. The first 3 or 4 ft. from the surface was earth, but the re- mainder was of seamy andesite rock. It was first proposed to use rock drilling machines, but the cheapness of manual labor, and the conditions being so as to permit of employing a great number of hands, induced the contractor to resort to the old method of drilling by hand. The average cost per cubic yard was I yen (about 50 cents), including drilling, blasting and the subsequent removal of the debris. For about one-third of the total length of the dock, near the entrance, the side walls were quite massive, the width of the bottom being 50 per cent of the height, but for the re- maining two-thirds of the length a thickness of only 4 ft. of concrete, with 2 ft. of cut-stone masonry, was considered sufficient to line the rock cutting. In the vicinity of the sill site, any deteriorated rock surface left after excavation was carefully removed, and trenches were cut to receive the con- crete sub-foundation, so that in some portions, just under the sill, for instance, the concreting is 14 ft. thick. For the main floor, however, the concrete layer upon the cleaned rock sur- face is only 2 ft. thick, upon which andesite cut-stone, 1 ft. thick, is laid. Cut stones are used only for the facing, coping and stepping, their backing being of concrete, so that, although the dock i is, to all appearance, of cut-stone masonry, the main portion of the material is concrete, The facing near the entrance and the coping and stepping are of granite, but the other parts of the masonry lining are of a cheaper material, andesite, and, to a careless observer, the dock seems to be granite throughout. ' The concrete used for important parts was of the follow- ing proportions: Portland cement I, sand 2, gravel 4; for the most part the concrete consisted of: Portland cement 1, puzzolana 1, sand 4, gravel 8. Puzzolana, which was con- veniently obtained from Goto Islands (off the coast of Naga- saki), was found to be of considerable advantage, both in reducing the cost of construction, and in improving the im- perviousness of the concrete. The wing walls are of concrete blocks made dry, and sunk in position. The proportions. of the ingredients for the concrete blocks were: Lime 0.25, puzzolana 1, Portland cement I, sand 4, gravel 8. -The pump-house is 24 x 76 ft., with its floor 11 ft. 7% in. above the main floor of the dock. The pump is 9 by 52 ft. arched with bricks, and with its bottom 22 ft. 11% in. below the pump-house floor. The space between the arch and the floor is one solid mass of concrete which resists the upward pressure of water by its dead weight. Four cast-iron suction pipes, each 33 in. in diameter pass through this thick concrete. Four sets of 33-in. centrifugal pumps, suitable for direct coupling to electric motors, were supplied by Messrs. Gwinnes, Ltd., England. The four pumps, together, are capable of discharging 16,000,000 gal. from the dock in 3 hours, when driven by the motors, each giving out 180 B. H. P., at a speed of 230 revolutions per minute. Under ordinary conditions, three of these pumps are used, the fourth being kept in reserve. One 9-in. pump for. drainage purposes, and one 6-in, charging pump, both mounted on the same bed-plate, are ar- ranged to be driven by a belt from one motor. Motors for the pumping plant, from Messrs. Siemens Brothers, are at work on a 220-volt continuous current. The current is taken through wires in ducts from the power plant common to all the workshops. In forming the steps to receive the side wall lining, blasting was forbidden, in order to avoid loosening the re- maining rock surface. The debris was removed by baskets on shoulders, and by hand-cars on light rails. When the excava- tion had been made to a considerable depth, a portion of rock was left at the middle of the dock to serve as an incline, and a winding engine pulled the hand-cars up to the surface of the ground. A number of women were employed on this work. The innovation of using modern excavators, locomotives, : _ machine drills, etc. may be suggested. No doubt the use of machines becomes economical when the amount of work 'is large enough to make the unit cost (including the machine's first cost) less than cheap manual labor, but when one consid- ers the local circumstances of the delay, the increased cost of importing the machines, the time required to train men in their proper use, and, further, the exceedingly cheap labor, say 20 to 25 cents per day, and the small amount of work to be done, there is not always an advantage in the use of machines. This was the case in the excavation of this dock. The estimated cost of construction for the dock proper at the beginning of the work was as follows: Temporary dam, together with its removal, 135,000 yen; side cutting, 90,000 yen; dock excavation, 120,000 yen; cut-stone masonry, 335,000 yen; concreting, 263,000. yen; building sheds, 21,000 yen; pumping during construction, 11,000 yen; timber works, 22,- 000 yen; puddling side of back walls, 6,000 yen; tools, 25,000 yen; sundries, 72,000 yen. Total 1,100,000 yen. Engine Wanted. Steeple compound engine; cylinders 9 and 18 by 14 in, stroke. Engine must be as good as new. In reply state price. Address Lock box 22, Cheboygan, Mich.