Alfred Ely Beach demonstrated a model of basic pneumatic subway system, in which air pressure in the tube pushed the cars, at the American Institute Exhibition in New York in 1867. After demonstrating that the model was viable, in 1869 Beach and his Beach Pneumatic Transit Company began constructing a pneumatically powered subway line beneath Broadway. Funneled through a company he set up, Beach put up $350,000 of his own money to pay for the full-scale test project. Built with a tunneling shield, the tunnel was complete in only 58 days. Its single tunnel, long, in diameter, was completed in 1870 and ran under Broadway from Warren Street to Murray Street.