Book excerpt: After the Civil War, the New York City's East River was a massive unsolved and dangerous navigation problem. A major waterway into and out of the Harbor--where customs revenue equaled 42 percent of the U.S. Government's income--the river's many hindrances, centered around Hell Gate, included whirlpools, rocks and reefs. These, combined with swirling currents and powerful tides, led to deaths, cargo losses and destruction of vessels. Charged with clearing the river, General John Newton of the Army Corps of Engineers went to work with the most rudimentary tools for diving, mining, lighting, pumping and drilling. His crews worked for 20 years, using a steam-drilling scow of his own design and a new and perilous explosive--nitroglycerine. In 1885, Newton destroyed the nine-acre Flood Rock with 282,730 pounds of high explosives. The demolition was watched by tens of thousands. This book chronicles the clearing of the East River and the ingenuity of the Army engineer whose work was praised by the National Academy of Sciences.