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Page:Popular Science Monthly Volume 89.djvu/552

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Popular Science Monthly

���Holding the Hudson back while the lounda- tion for the new piers was being prepared. Hundreds of tons of steel and thousands of tons of rock supported the sheet-piling cylinders

SO that the (Irilhng and blasting coukl be carried out close to the steel-sheet piling. To obtain the necessary rigidity, the smaller pockets were replaced by two great circular units fifty-fi\x' feet in iliamcter. These were filled with broken rock, which made them stable. The pressure developed in the cylinders made them watertight.

Along the stretch of cribbing a single line of interlocking steel-sheet jiilings had been <lri\en. When leakage oc- curred at that i)oint it was suggesti'd that the crevices be plugged by means of fluid cement or "grouting." The hea\'\' exj'iense of this remedy caused hesitation, and resort was made to another exjiedi- ent, this latter proving an effectise and

��cheap way of hailing the water. To begin with, a timber i)ile twelve inches in diameter was drivi-n down into the space back of the old cribbing, and then withdrawn, leaving a hole. This ca\ity was filled with a wadding composed of successive layers of earth, sawdust and manure, driven down hard by the pile which served the double purpose of ramrod and plug. In this fashion, a row of wooden pilings anil an eiiual number of water-tight wads were dri\en deep into liie underK ing earth, proving .inipK' sutlicient to stop all leaks. A little seepage, howe\er, came up from tile bare ri\er bed, but a small pumj) was sufficient to handle it. At Havana, pumps had to work constantly, and at

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