File:The American railway; its construction, development, management, and appliances (1889) (14574401098).jpg

Identifier: americanrailwayi00cool (find matches)
Title: The American railway; its construction, development, management, and appliances
Year: 1889 (1880s)
Authors: Cooley, Thomas McIntyre, 1824-1898 Clarke, Thomas Curtis, 1827-1901
Subjects: Railroads Railroads
Publisher: New York : C. Scribner's sons
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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nd in some cases resultsin more or less complete paralysis. The careful observations ofeminent physicians who have given this disease special attentionhave resulted in the formulation of rules which have reduced thedanger to a minimum. The execution of work within a deep pneumatic caisson is wortha moments consideration. Just above the surface of the wateris a busy force engaged in laying the solid blocks of masonrywhich are to support the structure. Great derricks lift the stonesand lay them in their proper position. Powerful pumps are forcingair, regularly and at uniform pressure, through tubes to the cham-ber below. Occasionally a stream of sand and water issues withsuch velocity from the discharge pipe that, in the night, the frictionof the particles causes it to look like a stream of living fire. Farbelow is another busy force. Under the great pressure and ab-normal supply of oxygen they work with an energy which makesit impossible to remain there more than a few hours. The water
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CRIBS FOR BRIDGE FOUNDATIONS. 75 from without is only kept from entering by the steady action of thepumps far above and beyond their control. An irregular settle-ment might overturn the structure. Should the descent of thecaisson be arrested by any solid underits edge, immediate and judicious actionmust be taken. If the obstruction be alog, it must be cut off outside the edgeand pulled into the chamber. Bouldersmust be undermined and often must bebroken up by blasting. The excavationmust be systematic and regular. A con-stant danorer menaces the lives of theseworkers, and the wonderful success withwhich they have accomplished what theyhave undertaken is entitled to notice andadmiration. Another process, which has succeeded =^=z:in carrying a foundation to greater depths Jthan is possible with compressed air, is —by building a crib or caisson, with cham-bers entirely open at the top, but havingthe alternate ones closed at the bottomand furnished with cutting edges. Theseclosed chambe

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