As shown below, only a small part of the coast line of the world is thoroughly surveyed. In the extensive ocean areas which are dotted with islands or reefs, a large amount of work is required for their sufficient charting, although many doubtful areas have been cleared up in recent years. Even the parts that are known to be of depths so great as to be free from navigational dangers should be sounded over sufficiently to develop the general configuration of the ocean bottom. Through international understanding a thorough exploration of all the water area of the globe and the coasts may in time be effected, and the many doubtful spots which still disfigure the charts may be either eliminated or definitely located. #Present state of progress of hydrographic surveys.# A comparatively small proportion of the coasts of the world can be considered as completely surveyed at the present time, and even such regions require much additional revision. In the class of more thoroughly surveyed coasts should be included the Atlantic and most of the Pacific coast of the United States, Porto Rico, nearly all the coasts of Europe, Algeria, and portions of the coasts of Japan, the Philippine Islands, and India. A large part of the world's coasts has been surveyed incompletely, but sufficiently well to permit the publication of navigational charts. This is the condition as respects most of southeastern Alaska and some other portions of the Alaskan coast, British Columbia, most of Mexico, Central America, the West Indies, Brazil and parts of Chile, the Hawaiian Islands, China, Malay Peninsula, Siam, the Dutch East Indies, Australia, New Zealand, Persia, Arabia, most of Africa, Iceland, northern Scandinavia, and Finland. Another considerable portion of the coasts has not been surveyed, but has been covered by explorations which have been embodied in nautical charts of varied degrees of incompleteness. In this class are the north coast and considerable portions of the south and west coasts of Alaska, the Aleutian Islands, Siberia, most of the oceanic groups in the Pacific, the northern coasts of Europe and North America, Greenland, the west coast of South America, Venezuela, and Argentina. Only a very small proportion of the total length of coasts is now entirely unexplored, and such portions are confined to the polar regions. #Chart publications of various nations.# There are about eighteen nations publishing navigational charts, and adding to the information on which charts are based. Many of these nations republish to some extent the charts prepared by the others. Great Britain has kept up a series of charts covering all parts of the world and practically including in some form all information published elsewhere. This series now (1908) includes 3725 different charts, of which the annual issue is about 600,000 copies. France (1906) publishes 2948 different charts.