The value of such publications has not been lessened by the gradual substitution of steam for sails on ocean-going vessels. While wind is no longer all-important, it is a factor in determining the speed, and hence the earning capacity, of all classes of ocean shipping, and the same is true of marine currents. Fog and drifting ice are, in general, more serious obstacles to steamers than to sailing ships. A glance at one of the Hydrographic Office Pilot Charts will suffice to show that these publications are indispensable to the mariner. On these charts we find, first of all, in the center of each five-degree square of latitude and longitude a “wind rose” showing the frequency of the winds that have been observed in that region from each of the cardinal points, and their average force from each direction. On the charts will also be found the routes recommended for full-power and low-power steamers and sailing vessels, lines of magnetic variation, tracks of storms in past years for the month in question, location and force of currents, average limits and prevalence of fog for the month, recent information about drifting ice and derelicts, descriptions of storm signals, and an abundance of other information of vital importance to the seaman. [Illustration: OCEAN WEATHER MAP PREPARED FROM VESSEL REPORTS JAN. 11, 1913, GREENWICH MEAN NOON _U. S. Weather Bureau_ Solid black lines are isobars. Arrows fly with the wind, the center of the arrowhead marking the position of the vessel, and the number of feathers denoting the force of the wind on the Beaufort scale. Shading of the head shows degree of cloudiness.]