#Information given on charts.# It is evident that it is impossible to represent on a chart of any practicable scale all the features that exist on the corresponding area of the earth's surface. It is essential, therefore, that a selection be made of the classes of facts that are to be shown, as well as of the detail that is to be used for each class. The practical utility of the chart depends largely on the good judgment used in this selection. In the information shown, charts differ from maps principally in representing by soundings and curves the configuration of the bottom of the water area, and in showing ordinarily the topographic features only in the vicinity of the coast line. The convenience of mariners should govern in the selection and arrangement of the information to be shown on charts, though they may be made useful for other purposes so long as this convenience is not lessened. The needs and preferences of navigators alone, however, differ so much that a reasonable chart must be somewhat of a compromise between conflicting views. For certain classes of navigation a boldly drawn chart showing only the dangers and a few other soundings and some landmarks might be useful. For other maritime purposes a more detailed chart would be valuable. The first, however, would fail to give facts often demanded in the navigational use of the chart, and the second if carried to an extreme would make a chart difficult to use. [Illustration: FIG. 5. STATE OF ADVANCEMENT OF HYDROGRAPHIC SURVEYS OF THE COASTS OF THE WORLD, 1904. _By G. W. Littlehales._ ]