Beschreibung

Kameraposition	38° 16′ 20,88″ N, 85° 45′ 47,35″ W	Dieses und weitere Bilder auf OpenStreetMap	38.272467; -85.763153

The original Fourteenth Street Bridge was completed in 1870. The deck spans of that bridge were built using the "Fink truss", designed by the Chief Engineer of the Louisville and Nashville Railroad, Albert Fink. In the mid-1870s, the bridge was acquired by the Pennsylvania Railroad. From 1916 to 1918, the bridge was rebuilt with a heavier superstructure atop the existing piers, which had to be reduced in height to accomodate the new spans. The Penn Central (formed by the 1968 merger of the Pennsylvania and New York Central Railroads) went bankrupt in 1970 after less than 3 years in existence. In 1976, the bridge was acquired by the Consolidated Rail Corporation (Conrail), and in 1994, it was sold to the Louisville and Indiana (L&I) Railroad.

The large span at upper left crosses over what was known as the Indiana Chute. This was one of three routes historically taken by boats traveling through the Falls of the Ohio, the others being the Kentucky Chute and the Middle Chute. Dam No. 41. as it was called from about 1914 to 1960, had a navigable pass, so that when the river was high enough, a section of dam could be lowered, allowing boats to travel through the Indiana Chute, thereby saving the time required to travel through the Portland Canal and locks. When the dam (renamed McAlpine Dam) was rebuilt in the early 1960s, the navigable pass was permanently encased in concrete and incorporated into the new dam. The Indiana Chute span is 644 feet long, making it the "longest and heaviest simple-truss riveted span in existence" at the time it was built (accd. to Engineering News-Record, 82 (21): 1007, May 22, 1919). At right is the 370-foot span over the old Middle Chute, which now allows vessel access to the upstream face of the hydro-electric plant.

Just upstream from the bridge are five Tainter gates (named for inventor and engineer Jeremiah Burnham Tainter) which, together with four more gates near the hydro-electric plant, control the flow of water through the dam. When the water level above the dam gets too high, the gates can be raised, singly or in combination, to let the water flow under them. As seen in this photo, a small amount of water flows under the gates even when they are closed.

In the foreground is part of the limestone bedrock which forms the Falls of the Ohio. The coralline zone is the lowest layer of the Jeffersonville Limestone (named for the nearby city), which in this area is about 25 to 35 feet thick, depending on where it is measured. The coralline zone is about 8 to 11 feet thick and is named for the many species of fossil coral found in it. This limestone dates back to the middle Devonian Period, about 375 million years ago, when the continental plates were arranged much differently than today. The Falls area at that time was nearer to the equator, the bed of a shallow tropical sea, somewhat like the Bahamas today. Many of the animals in the sea had calcium carbonate shells or skeletons which settled to the bottom when they died. Together with the waste products of living animals, the remains formed a sediment which over time lithified into limestone. Much later in geological time, during the last 10,000 years, the Ohio River eroded down through glacial deposits until it reached the limestone bedrock seen at the Falls. Before the dam was built, the bedrock was exposed at low water across the entire width of the Ohio River, forming rapids about 2 miles long with a drop of about 26 feet. These rapids, known as the Falls of the Ohio, were a natural barrier to navigation and stimulated the early development of Louisville, Jeffersonville, Clarksville and New Albany.

See
Powell, Richard L., 1970 (revised 1999). Geology of the Falls of the Ohio River: Indiana Geological Survey Circular 10.
and
Conkin, James E., and Conkin, Barbara M., 1980. Handbook of Strata and Fossils at the Falls of the Ohio: University of Louisville Studies in Paleontology and Stratigraphy.

Ohio River mile 605
Clarksville, Clark County, Indiana
22-August-2005
File # A5H005

scanned from 6x9 cm Kodak Portra 160VC negative

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