Notwithstanding the great progress made in hydrographic surveys, a considerable number of rocks and shoals dangerous to navigation and not previously shown on the charts are reported, averaging nearly 400 each year for the last six years, according to the British reports. Of the 367 reported in 1906, 11 were discovered by vessels striking them. Immediate information in the form of _Notices to Mariners_ is published, of the more important corrections to charts which can be made by hand. These corrections show what charts are affected, and give sufficient data for plotting. In the case of extensive corrections or new surveys a new edition of the chart is printed and all existing copies of the previous edition are canceled. It is important that the user of the chart shall make certain that he has the latest edition and that all corrections from its date of issue have been applied from the _Notices to Mariners_. It is unfortunately true that owing to failure to take proper account of the notices, or to economy, old editions or unconnected charts are sometimes used, and in a number of cases the loss of vessels has been directly due to this cause. Those responsible for the safe navigation of vessels should insist that the latest editions of charts are provided and that all charts to be used are inspected and corrected to date. READING AND USING CHARTS. #Reading charts.# A chart is a representation on paper of hydrographic and topographic information by means of various conventional methods and symbols. It is evidently important for those making use of charts to understand the system and conventions used, and to be able to interpret readily the various parts of the chart. The ability to read a chart must include an understanding of all its features, such as scale, projection, geographic position, directions, depths, plane of reference, aids to navigation, tides, currents, elevations, topography, and date of survey and publication. #Scale.# For American and British charts the scale is usually expressed by the inches or fractions of an inch to the minute or degree of latitude, or by the fractional proportion of a distance on the map to the corresponding distance on the earth. These fractions are sometimes stated on the British charts, and nearly always on those of the United States Coast Survey. The chart catalogues give the scale in one or the other form. A familiarity with the meaning of scales is of value in selecting the most suitable chart, in judging of the relative uses of charts, and in estimating distances. Where the fractional scales are stated they furnish a simple means of comparing charts, as, for instance, a chart on 1/50000 scale will show all distances just twice as long as a chart on 1/100000 scale. The following are scale equivalents: