Henry David Thoreau investigated the Sudbury River as America's first river scientist.Robert M. Thorson The steam locomotive chugged its way toward Cambridge, Massachusetts, on Aug. 15, 1859. On board was an impatient young scientist wanting to understand the math and science governing how river channels should behave. After disembarking at Harvard College and searching the stacks of its library, Henry David Thoreau checked out “Principes D’Hydraulique,” a three-volume tome of hydraulic engineering.