SINKING BRIDGE PIERS.
Freeport, Ill.
Please explain the use of compressed air in sinking the caissons of the great Brooklyn and New York bridge.
F. R. Smith.
Answer.—The method of sinking cylinders by use of compressed air was invented by Mr. Triger, of England, in 1841, but has been carried to greater results in the United States than anywhere else. Tubular cast-iron shells are used to form a large hollow pile, which may be forced downward by its own weight and superincumbent masonry built on it as it descends. Compressed air is employed inside such shells to force the water out at the bottom, where the pile or caisson is open, while it is air-tight and water-tight at all other points. It was formerly supposed men could not work under a pressure of more than three atmospheres, which is required in most cases to keep out water at a depth of sixty-five feet, but in the case of the St. Louis bridge, caissons were sunk a depth of 110 feet below the surface. So, in the case of sinking the Brooklyn bridge piers, the men at work in the compressed air chamber, excavating the earth as the pier descended, worked in an atmosphere from three to four times as heavy as in the open air; a strain which they could endure but a short while at a time, and which proved fatal in many instances.
PROPERTY OF ALIENS.
Griswold, Iowa.
If a Welshman who has not been naturalized dies in this country, who inherits his estate? Would the making of a will make any material difference as to the control of his property?