Building The Brooklyn Bridge New York, 1920s - Film 33827

How was the Brooklyn bridge was built in New York. Film continues to show how a tunnel was then built under the river.
Film starts with views of the finished bridge. Diagrams show how the building was engineered. Problem 1 - How to build the foundations underwater. Pile driving. Foundation structures are pushed into the river. Maasonry structures of the towers being built.
Problem 2 - How to hang a giant bridge span across the river. More diagrams demonstrate the building. A rope was tied to a pier and pulled across the river by boat. Attached to the opposite pier it was then pulled tight. Cables were hauled across one of one. Four cables each contained over 5,000 wires. Suspenders hung from the cables and the roadway built at the same time from both sides of the river to meet in the middle. Most of the footage is diagram format.
Engineers working in a factory or laboratory, testing theories, experiments. Teaching young engineering students. A man works on a car engine. A glass door, name says Mechanical Engineer, S Mc Grath. Group of men sit around a table discussing plans. A construction site, two men stand at one corner discussing plans. A diagram indicates the educational path taken by an engineer.
View of the Brooklyn Bridge with river traffic passing underneath. Repeat of footage of engineers meeting around a table. Cover of a report - proposed tunnel sites. Traffic congestion on the Brooklyn Bridge, means a tunnel is now required under the river. Pieces of paper list the steps taken in planning the tunnel - possible sites, funding, area improvement, tolls, geology, cost comparisons between another bridge, a tunnel or ferry services. Again Engineers pour over maps and plans around their meeting table. Using diagrams the engineering requirements of a 3,500 feet tunnel are explained. Shafts are sunk and tunnels driven. Actual footage of the shaft structures and digger buckets removing soil. A section of tunnel, showing concrete reinforcement girdles being positioned. Loading plates - the tunnel is lined with cast iron rings. Actual footage of these rings being moved on tracks and lowered down a lift shaft to the tunnel. Workers collect the load at the bottom of the lift.
Problem 3 - How to build the tunnel so it won't collapse under the weight of water above. Men entering an air lock. Problem 4 - Making walls water tight. Worker attaching huge nuts and bolts in the tunnel and using an equally large spanner to tighten them. Joint are sealed. Rocks packed around the cast iron rings before being concreted to fill all gaps. View down the partially completed tunnel.