R. Hassler, was selected to lead the Survey. Hassler submitted a plan for the survey work involving the use of triangulation to ensure scientific accuracy of surveys, but international relations prevented the new Survey of the Coast from beginning its work; the Embargo Act of 1807 brought American overseas trade virtually to a halt only a month after Hassler's appointment and remained in effect until Jefferson left office in March 1809. It was not until 1811 that Jefferson's successor, President James Madison, sent Hassler to Europe to purchase the instruments necessary to conduct the planned survey, as well as standardised weights and measures. Hassler departed on 29 August 1811, but eight months later, while he was in England, the War of 1812 broke out, forcing him to remain in Europe until its conclusion in 1815. Hassler did not return to the United States until 16 August 1815. The Survey finally began surveying operations in 1816, when Hassler started work in the vicinity of New York City. The first baseline was measured and verified in 1817. The unit of length to which all distances measured in the U. S. coast survey would be referred was the Committee metre (French : Mètre des Archives), of which Ferdinand Rudolph Hassler had brought a copy in the United States in 1805. In 1835, the invention of the telegraph by Samuel Morse allowed new progresses in the field of geodesy as longitudes were determined with greater accuracy. Moreover, the publication in 1838 of Friedrich Wilhelm Bessel’s Gradmessung in Ostpreussen marked a new era in the science of geodesy. Here was found the method of least squares applied to the calculation of a network of triangles and the reduction of the observations generally. The systematic manner in which all the observations were taken with the view of securing final results of extreme accuracy was admirable. For his survey Bessel used a copy of the Toise of Peru constructed in 1823 by Fortin in Paris. In 1860, the Russian Government at the instance of Otto Wilhelm von Struve invited the Governments of Belgium, France, Prussia and England to connect their triangulations in order to measure the length of an arc of parallel in latitude 52° and to test the accuracy of the figure and dimensions of the Earth, as derived from the measurements of arc of meridian. In order to combine the measurements it was necessary to