A 706-foot boring machine cut north under the Potomac all summer with most of its body still parked in the daylight, while a crane fed the rest down a 100-foot shaft 30 tons at a time, and with the last car bolted on it has 350 feet to go before it stops for two mont – autonocion.com

A 706-foot boring machine cut north under the Potomac all summer with most of its body still parked in the daylight, while a crane fed the rest down a 100-foot shaft 30 tons at a time, and with the last car bolted on it has 350 feet to go before it stops for two mont