Workers from both sides continued working on the tunnel, mining caverns until the tubes from each side connected with each other. In July 1947, the eastern tube for future northbound traffic was the first to be holed-through, with workers from each side shaking hands as a small pipe was passed through from one side to another. The pipe was then removed, and the openings covered up, to prevent drastic changes in pressure at either end of the tube. The tunnels from Manhattan and Brooklyn had connected at a point under Governors Island, with an error of , and work continued until there was enough assurances that the tunnels had equal pressure readings.