In July and August of this year Canada is hosting four international organization concerned with the exploration and development of the earth and man's activities on the planet. More than 15,000 delegates from some 125 countries will take part in various activities of the 22nd International Geographical Congress, the 24th International Geological Congress, the 6th International Conference of the International Cartographic Association and the 12th Congress of the International Society of Photogrammetry, the major assemblies of which are being held in Montreal and Ottawa. The presence in Canada of these four international organizations gives implicit recognition to the work of Canadians in the field of earth sciences. The release of four appropriate Canada Post Office stamps, each with a denominative value suitable for use on mail destined for a large part of the earth's surface, provides evidence of the significance attached to these events in the host country. A simplification of mountains drawn in schematic shape by using "Siegfried" lines, used in Cartography in three-dimensional maps, appears on the stamp which provides recognition for the 6th International Conference of the International Cartographic Association. This conference will stimulate interest in a subject which is of immediate interest in environmental sciences and in the work of developing and administering countries and their resources by encouraging an effective exchange of ideas between experts.