The Practical mechanic's journal . ave, within the last few days, completed the foundations of a pierfor the Springfield Bridge over the river lrwell, by means of a contriv-ance of a similar nature. The arrangement to which I refer is a portable coffer-dam, formed bytwo cylinders composed of g inch wrought-iron plates riveted together,the outer one being 9 feet, and the inner one 6 feet 6 inches diameter,and both 8 feet high. The depth of the river varies from 4 to 7 feet, sothat the iron cylinders, when placed in the deepest part of the river, wereabout a foot above the water level. The curre
The Practical mechanic's journal . ave, within the last few days, completed the foundations of a pierfor the Springfield Bridge over the river lrwell, by means of a contriv-ance of a similar nature. The arrangement to which I refer is a portable coffer-dam, formed bytwo cylinders composed of g inch wrought-iron plates riveted together,the outer one being 9 feet, and the inner one 6 feet 6 inches diameter,and both 8 feet high. The depth of the river varies from 4 to 7 feet, sothat the iron cylinders, when placed in the deepest part of the river, wereabout a foot above the water level. The current in the lrwell being rather strong at the point where theSpringfield Bridge is now erecting, it was found necessary to lay down acut-water at each end of the pier, which is composed of five stone annexed sketch is a plan of the whole pier, showmg the two cylin-ders serving as a coffer-dam. The whole of the pillars are united bystrong wrought-iron cramps above the water line, and carry a stone en-tablature at the The cylinders having been placed in the middle of the stream, andsunk as low as possible through the loose gravel at the bottom, 1 had allthe loose stones removed from the annular space between the two, andfilled it with strong puddle, made of clay and straw well worked toge-ther. The water was then pumped out of the inner cylinder, until thebed of the river was in sight. In those parts where the cylinders touchedthe rock, the joint was perfect; but in one place a little water found itsway in, owing to the bed of the river being partly composed of leakage was, however, easily stopped by driving in a few 3-inchsheet piles. After clearing away about two feet of the rock and stonesfrom the bed of the river, an excellent foundation was obtained, and thefirst stone was laid, as seen in the sectional view of the dam—a hand-pump of 4 inches bore being sufficient to keep the interior free from dripwater. The whole apparatus answered so well, tha
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Keywords: ., bookcentury1800, bookdecade1840, bookidpra, booksubjecttechnology
