(1) The science dealing with the physical features (geometry and dynamics) of the surface waters of the Earth. Hydrography differs from physical oceanography in that it deals with rivers and lakes as well as with oceans and seas. It differs from hydrology in dealing with only surficial waters and not with underground waters. (2) The science dealing with the geometric features of the surface waters of the Earth. In this sense, the term is practically synonymous with charting. (3) The science dealing with the surface waters of the Earth. This appears to be the term's original meaning. However, present custom is to use the term oceanography instead, if marine waters are being considered and hydrology if rivers, lakes, etc., are being considered also. (4) That branch of physical oceanography dealing with the measurement and definition of the configuration of the bottoms and adjacent land regions of oceans, lakes, rivers, harbors and other forms of water on the Earth. (5) The science and art of measuring the oceans, seas, rivers, and other waters, with their marginal lands, inclusive of all the fundamental elements which have to be known for the safe navigation of such regions, and the publication of such information in a form suitable for the use of navigators. This definition resembles definition (2) but is much less general in that it excludes all subjects not concerned with navigation or concerned with navigation but not published. It does include measurement of marginal land, however. (6) That science which deals with the measurement and description of the physical features of the oceans, seas, lakes, rivers and their adjoining coastal regions, with particular attention to the use for navigational purposes.