Context of Drainage basin of the Potomac. Letter from the Secretary of the Interior, transmitting, in response to resolution of the Senate of January 14, 1898, a copy of a letter from the Director of the Geological Survey inclosing a report regarding the hydrography of the drainage basin of the Potomac. January 25, 1898. -- Referred to the Committee on Public Health and National Quarantine and ordered to be printed.