Established in 1807 and known as the United States Coast Survey until 1880, the Coast and Geodetic Survey was primarily involved in geodesy, or geodetic measurement, the survey of large land areas in which mathematical corrections are made to take into account the curvature of the earth's surface. In 1871, at the urging of Coast Survey supervisor Benjamin Peirce, Congress appropriated funds to make a "geodetic connection" between the two coasts. They used an astronomical method recently devised by American engineer Andrew Talcott for determining latitude and employed the electric telegraph for finding longitude—taking advantage of new technology to improve the accuracy of their measurements. (Old methods of calculating longitude were accurate to one thousand feet; with the electric telegraph the margin of error was only one hundred feet.) The survey proceeded slowly from east to west using triangulation. In this process, once...