It was in response to the demand for easy
transportation that the system for India-rubber pontoons was elaborated.
Single supporting cylinders of rubber-coated canvas were first
experimentally used in 1836 by Captain John F. Lane, United States army,
on the Tallapoosa and Chattahoochee Rivers in Alabama. The
service-pontoon, as arranged by General Cullum, is composed of three
connected cylinders of rubber-coated canvas, each having three
compartments. On these pontoons, when inflated, the bridge-table is
built, lashed, and anchored. This bridge has remarkable portability, but
it has also serious defects. The oxidation of the sulphur in vulcanized
rubber produces sulphuric acid in sufficient amount to impair the
strength of the canvas-fibres, thus causing eventual decay, rendering it
prudent to renew the pontoons after a year's campaigning. The pontoons
are required to be air-tight, and are temporarily made partially useless
by punctures, bullet-holes, rents and chafings, although they are easily
repaired. Hence this bridge, despite its portability, is hardly equal to
all the requirements of service, though it was the main dependence in
Banks's operations in Louisiana, and was successfully used in Grant's
Mississippi campaign.
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