He found himself, however, unable to relinquish his interest in the affairs of his " first love," the Coast Survey, and when, at the outbreak of the civil war, Superintendent Bache appealed to him to return and lend his aid in supporting the Survey, when its very existence was threatened as a measure of ill-understood economy, he promptly dissolved his lucrative business connection and repaired to Washington, where he brought strong arguments to bear upon Schuyler Colfax and Roscoe Conkling (eminent as leaders in the dominant party), showing how important such an organization as the Coast Survey must be to the country in time of war. At first, Conkling's close and critical examination of his argument led Hilgard to believe him actuated by a spirit hostile to the Survey; but he was greatly relieved to find, soon afterward, that he had converted both men into earnest and active supporters of the work. Subsequently he took an active part in organizing the National Academy of Sciences, of which he became a charter member; he also contributed largely to the investigations made by that body for the Government.