#The depth curves# on charts furnish a valuable guide, and if the curves are lacking or broken in some parts it is usually a sign that the information is incomplete. The 100-fathom curve is a general warning of approach to the coast. The 10-fathom curve on rocky coasts should be considered as a danger curve, and caution used after crossing it. The 5-fathom curve is the most important for modern vessels of medium draft, as it indicates for them the practical limit of navigation. The 3, 2, and 1-fathom curves are a guide to smaller vessels, but have less significance than formerly because of the increase of draft of vessels. #The shrinkage of paper#, especially in plate printing, has been referred to. This introduces two possible sources of error: first, the shrinkage being different in the two directions, any scale printed on the chart will be accurate only when used in a direction parallel to itself; second, for the same reason, angles and directions will be somewhat distorted. Fortunately these errors are not serious in the ordinary navigational use of a chart, but they should not be overlooked when accurate plotting or measuring of distances is attempted on a plate-printed chart. The actual shrinkage measured on charts printed from plates varies from 1/3 inch to 1 inch in a length of chart of 36 inches. On British and American plate printed charts the shrinkage is usually from two to nearly three times as much in one direction as it is in the other. #Care of charts.# In order that they may be properly used charts should be filed flat and not rolled. They should be systematically arranged so that the desired chart can be instantly found. They should be cared for and when in bad condition replaced by new copies. They can be most conveniently filed in shallow drawers, thus avoiding the placing of many charts in a single drawer. The latter is a common fault; it not only increases the labor of handling the charts but adds to the liability of their injury. PUBLICATIONS SUPPLEMENTING NAUTICAL CHARTS. There are several publications in book and in chart form which are either necessary or convenient for use in connection with nautical charts. These comprise the coast pilots, notices to mariners, tide tables, light and buoy lists, and various special charts. #Coast pilots#, or sailing directions, are books giving descriptions of the main features, as far as of interest to seamen, of the coast and adjacent waters, with directions for navigation. They contain much miscellaneous information of value to the mariner, especially the stranger. Although they contain additional facts which cannot be shown on the charts, they are not at all intended to supersede the latter; the mariner should in general rely on the charts. The sailing directions can be less readily corrected than the charts, and in all cases where they differ the charts are to be taken as the guide.