In 1887 France’s Ferdinand Arnodin, the son of a bridge inspector, received the first patent for an aerial transporter bridge, often called a “transfer bridge” or “ferry bridge.” Three years later he and Spain’s M. Alberto Palacio, a disciple of Paris tower designer Gustav Eiffel, together received a patent for a similar bridge for the “means of transporting goods.”
The bridge essentially worked like this: A suspension bridge sat atop two steel towers built on piers placed along opposite banks of a waterway. A gondola car was suspended from the top span with cables attached to pulleys that ran along the structure’s bottom rail, which was high enough to allow marine traffic to pass beneath it. A submerged chain, connected to piers along either bank, was looped over a drum on the gondola car. An electric streetcar motor turned the drum, which in turn moved the cables, and so the gondola car essentially pulled itself back and forth above the water. The cable simply lay along the bottom of the canal when not in use, but while the ferry car was in operation it would naturally be pulled out of the water in front of the car and the slack of the cable would sink back down behind the car and out of the way of shipping traffic as it crossed the river.
Palacio adapted his and Arnodin’s patent for Spain’s Vizcaya Bridge, which connects the towns of Portugalete and Las Arenas at the mouth of the Nervion River. With Arnodin’s help, the 147-foot-high bridge spans 525 feet was completed in 1893 and was the first of its kind in the world, carrying goods, wagon traffic, and people from a suspended gondola. Palacio’s bridge is regarded as “one of the outstanding architectural iron constructions of the Industrial Revolution.” After nearly 130 years of service, The span still crosses the Nervion River every eight minutes during the day and hourly at night, carrying up to six cars and dozens of passengers on the ninety-second trip. Officials estimate the 4 million people and half a million cars use it every year.
But it was Arnodin’s 1899 transfer bridge spanning the River Seine in Rouen, France, that inspired a Duluth engineer’s idea to span the city’s ship canal. The bridge’s towers stood 220 feet above the piers along the banks of the Seine. It stretched 469 feet across the river, and its span rested 164 feet above the water. The ferry car, forty-two feet long and thirty-three feet wide, sat twenty-three feet above the water. It had two cabins, one with windows, the other without: First class and second class (first class cost ten centimes and second class five). The bridge crossed the river in just fifty-five seconds and served the city until 1940, when French Army engineers destroyed the bridge in a futile attempt to slow the advancing German army.When Duluth’s aerial bridge went into service in 1905, transfer bridges were also in use in Newport, Wales (also an Arnodin design); Bizerte, Tunisia; and over the River Loire in Nantes, France. Since then two dozen transporter bridges have been built in eight countries including Spain, France, Germany, England, Czechia, Tunisia, the Netherlands, Argentina, and Brazil. Thirteen of them—including the Duluth bridge—still stand. Arnodin is thought to have designed at least nine of them, three of which remain in operation.