Secondary Source

By 1881, he had established an engineering practice in Pittsburgh, where he built several bridges, including the Smithfield Street Bridge, a stunning example of the lenticular truss. Lindenthal also worked on a variety of railroad projects, including surveying and estimating for rail lines in Pennsylvania and the reconstruction of bridges on what is now the Erie Railroad. In 1885, officials with the Pennsylvania Railroad approached him with a project thtat, although he never got to build it, would fascinate him the rest of his life—a bridge across the Hudson River to link New York City with New Jersey.

Despite its pioneering technology in 1779, as the first structural use of cast iron, no eye witness accounts are known which describe the Iron Bridge being erected. However, recent discoveries, research and experiments have shed new light on the mystery of exactly how it was built, challenging the assumptions of recent decades. In 1997 a small watercolour sketch by Elias Martin came to light in Stockholm. Although there are a wealth of early views of the Bridge by numerous artists, this is the only one which actually shows it under construction.

The current structure is the third bridge on this site. Lewis Wernwag built the covered wooden Monongahela Bridge in 1818, the first river crossing bridge in Pittsburgh. It replaced a ferry and cost $102,000. It was destroyed in the Great Fire of 1845 and replaced the following year.
Drawing of 1818 bridge

John Roebling, creator of the Brooklyn Bridge, designed a wire rope suspension bridge which used the 6 piers and abutments from the earlier bridge (8 spans, 188 ft each). Roebling's first highway bridge operated as a toll bridge. Increasing live loads from added traffic resulted in excessive deflections and swaying, leading to its closure and replacement with current structure.

Lennox Bridge is the oldest surviving bridge on the Australian mainland. This sandstone, single arched bridge is situated in a bushland setting on the eastern escarpment of the Blue Mountains of New South Wales and is well worth a visit. The bridge can now only be approached from the western side along Mitchell’s Pass. Once across the bridge, the roadway changes to one way traffic down the Pass.

Firstly a base was laid down to cover the area of two of the ribs. The white bar coming from centre RHS is the radial pole for positioning the pattern equipment. The red pieces among the men are the pieces of patterns used. Segments of the rib were rammed with sand and then moved to form the next section of the mould.
The mould was 36 feet long with a cross section of the rib being 4.5" x 3".
The blue machine above the radial pole is the sand mixer. This mixer is computer controlled to allow resins and catalysts to be mixed with reclaimed sand. The temperature of the sand, ambient temperature and speed at which we require it to set are controlled automatically. The sand it produces is used to make the mould, into which we will pour the molten iron. It was imperative to have a flat bed as the iron like water would find its own level, if we were too high at one end the metal would overflow at the other and provide the BBC with a floor of metal.

Lennox's arrival in New South Wales opened a new chapter in the bridge-building history of the colony. He built a series of stone bridges, some of which are still standing. In 1844 he moved to Melbourne, where he had charge of all roads, bridges, wharves and ferries, acted as advisory engineer to various government departments and built 53 bridges.
Career Highlights:
Born Ayr, Scotland. Arrived Sydney 1832; Sub-Inspector of Roads 1832-33; Superintendent of Bridges 1833-43; district surveyor to the Parramatta Council 1843-44; Superintendent of Bridges, Port Phillip District 1844-53. Built a number of stone bridges, including one on the main western road at Lapstone Hill, the Lansdowne Bridge on the main southern road near Liverpool, the Lennox Bridge over the Parramatta River and the first Prince's Bridge over the Yarra River in Melbourne.

The use of coke as a fuel to smelt iron had been attempted in the second half of the 17th Century, but the first successful process was established by Abraham Darby around 1709 at his newly acquired ironworks in the Coalbrookdale, Shropshire. This was a major industrial breakthrough because it allowed the casting of much larger pieces than the old charcoal fuel process, which had been largely restricted to pots and kettles. Darby’s achievement in mastering the coke smelting process enabled this small valley in Shropshire to become the cradle of the world’s industrial revolution. The products of Darby’s ironworks were shipped down the River Severn by barge to Bristol and thence all over Britain and progressively outwards to Europe and the rest of the world.

John Roebling was enthusiastic.

"No other part of the East River offers a locality so favorable to bridging," the great engineer wrote to the New York businessmen who proposed building a span to link Manhattan and Long Island.

But the East River bridge that so interested Roebling was not the Brooklyn Bridge that would be the cornerstone of his enduring fame. This span -- proposed in 1856, more than a decade before the Brooklyn Bridge project took form in 1867 -- was what would become the Queensboro Bridge.

Upper Delaware Scenic and Recreational River is the home of the oldest existing wire suspension bridge in the United States — the Delaware Aqueduct, or Roebling Bridge as it is now known. Begun in 1847 as one of four suspension aqueducts on the Delaware and Hudson Canal, it was designed by and built under the supervision of John A. Roebling, future engineer of the Brooklyn Bridge.

Portions of the D & H Canal, including the Delaware Aqueduct, were designated a National Historic Landmark in 1968. The Delaware Aqueduct is also designated a National Civil Engineering Landmark.

...A German immigrant, and graduate of the Royal Polytechnic School of Berlin, Roebling came to the United States in 1831. It was not until 1845 that he built his first suspension structure. From 1845 until his death in 1869, he designed five major suspension bridges. Two — the Cincinnati-Covington Bridge and the Brooklyn Bridge — are still standing.

On June 12, 1806, John A. Roebling, civil engineer and designer of the Brooklyn Bridge, was born in Muehlhausen, Prussia. The Brooklyn Bridge, Roebling's greatest achievement, spans the East River to connect Manhattan with Brooklyn. For nearly a decade after its completion, the bridge, with a main span of 1595 feet, was the longest suspension bridge in the world. Steel wire cable, invented and manufactured by Roebling, made the structure possible.

When the Brooklyn Bridge was opened you had to pay three cents to cross it until it was paid for. When they opened the bridge everybody went to see it..It took them 14 years to build the Brooklyn bridge.