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842 for a traveller or business man to ask for a sheet of the international map of the region in which he intends to travel. For students of geography or history this series, covering the world with maps on a uniform plan, will be indispensable.

In the printing of sheets of the map, perhaps the most difficult matter is to ensure that the hypsometric, 'or " layer," tints, which show the successive altitudes of the terrain, shall be strictly in accordance with the agreed system. To assist in this the resolutions are accompanied by a detailed diagram in colour, which serves to show the exact shade of each colour printing.

The Paris Conference, in addition to passing the very practi- cal resolutions described above, took an important step in approv- ing of the establishment of a " Bureau Permanent," comprising a central office to be located at the headquarters of the Ordnance Survey at Southampton, with a branch office in London. The functions of the Bureau are: the publication of an annual report on the progress of the scheme; the organization of a service of exchange of information; and the criticism, when desired, of proofs, drawings .or impressions. Of these functions the first two are the most important. The branch, or auxiliary, office in London is the Royal Geographical Society, where visitors to London can obtain all information with regard to the Interna- tional Map and its progress. The Director-General of the Ord- nance Survey is ex-officio Director of the Bureau.

The Paris Conference came to an end on Dec. 18 1913, but the Report of this Conference was not published when war broke out early in Aug. 1914. The effect of the war on the scheme was twofold. First, it resulted in the immediate cessation of all work en the map so far as the belligerent countries were concerned; but in the second place it led to a demand for maps on, or about, the one-to-a-million scale, and so in England and France, particu- larly the former, much official cartography was carried out on the million scale, and a large series of maps was produced by the initiative of the General Staff. The General Staff series of maps was for the most part designed by a special staff of experts at the Royal Geographical Society, and was fair-drawn and printed by the Ordnance Survey. It adheres to the sheet lines and pro- jection of the International Map and to a good many of the conventions, but it is not hypsometrically coloured, and from the nature of the case is somewhat roughly produced. It is, however, an important series and comprises ninety maps extend- ing from the Persian Gulf to the Arctic Ocean, and from the western shores of Ireland to beyond the Caspian Sea. Covering as it does so important a part of tile world's surface, it is of value to geography on account of its uniformity and general accuracy. A high compliment was paid to this series when its sheets were selected by the Peace Conference for use in determining the new European frontiers, and the Geographical Section of the British General Staff is to be congratulated on its foresight in arranging for its preparation. It differs from the regular inter- national series, not only in small technical details, but also in the fact that the sheets were produced by one country and not by the countries represented; it is an essential element in the con- struction of the regular series that each country produces its own sheets, and where a sheet includes portions of two or more coun- tries the sheet will be undertaken by one of them, after agree- ment with the others.

The International Map, so rudely interrupted by the war, has since been taken up again, and satisfactory progress has con- tinued to be made.

At the cjose of 1920 maps were in hand, or had been published, by the following countries: Brazil, Canada, Chile, Denmark, Egypt, France, Great Britain, India, Italy, Japan, Portugal, Rumania, Siam, Spain, Sweden, United States, Uruguay. Thirty-six sheets had been printed and 102 were in various stages of preparation. The main continents and islands would take about 800 sheets to cover, so that a very substantial beginning amounting to about one- sixth of the full total had been made. Of course there are many parts of the world insufficiently explored for the exact information required by the regular sheets of the series, but provisional editions can be published of these sheets, and their very incompleteness will give a stimulus to exploration. The most striking group of sheets already available is that published by the Survey of India; but important blocks of sheets were, at the opening of 1921, due for early issue by the United States Geological Survey (which carries out most of the official cartography of the United States), and by Brazil and other States of South America.

War Maps. The trench warfare of 1914-8 in France and Belgium created a demand for maps on a larger scale than had hitherto been in general use by great armies. Before the war, for instance, the French had been content with the black Carte de I'etat major on the scale of i : 80,000, for the new map on the scale of i : 50,000, of which very few sheets have been printed, was evidently not taken very seriously as a military map. On the outbreak of war, in Aug. 1914, the only map of N.E. France available for the French and British armies was this i : 80,000 map, except that for certain areas round fortresses there existed the so-called " plans directeurs " on the scale of i : 20,000. In Belgium the cartographic situation was much better. Belgium was covered by an excellent series of maps, based on field sur- veys and original drawings on the scale of i: 10,000. The pub- lished Belgian maps were on the scales of i : 20,000, i : 40,000, i : 100,000 and i : 160,000. The Germans, however, also possessed these maps, so that the Allied armies had no advantage in this respect. An immediate effect of the rapid stabilizing of the position on the Franco-Belgian front was that large-scale maps became indispensable for the operations of trench warfare, particularly in connexion with the use of artillery.

With regard to that portion of the line which passed through N.E. France all that could at first be done was to enlarge the i : 80,000 to i : 20,000. Of course such an enlargement made an unreliable map, with errors of hundreds of metres, and, bit by bit, these enlargements were corrected. But the mere correction of inaccurate enlargements can never make a reliable map, and even- tually all the maps of the western front were redrawn from special surveys, air photographs and revised cadastral manu- scripts. The methods are described in the article SURVEY. It is sufficient to note here that the chief scales in use were those of i : 20,000 and i : 40,000; that the former scale showed the enemy's trench system in detail, and that all the maps were provided with a system of " squares," or coordinates, which enabled any point to be defined within a few metres. The use of " squares," or co- ordinates, is typical of modern military maps. An example of a typical trench map of the western front on the scale of i : 20,000 is shown on Plate II. The number of maps issued to the troops was very large, greatly exceeding all previous anticipa- tions. The Ordnance Survey alone printed 32 millions of trench and other war maps during the four years and three months that the war lasted, and to this must be added the maps printed by the survey battalions in the field. Altogether the British armies in France and Belgium used some forty million maps.

The Progress of Cartography. A very noticeable feature of all modern topographical maps is the increasing use of colour. The old, black, engraved maps are disappearing one by one. But however beautiful these maps were as specimens of engraving, they were never very easy to read, and in no case did they convey so much, or such accurate, information as do the modern topo- graphical maps printed in five or six colours. However artistic a black, hachured map may be it is far less exact in the representa- tion of hill forms than a coloured, contoured map. But it is doubtful how long the modern coloured map will last ; the paper is not nearly so durable as that which is used for the printing of copper-engraved maps; and the colours are in some cases none too permanent. Perhaps in some cases in which the maps are kept in dry presses away from the light they may last for a hundred years or so; but our remote descendants can hardly be expected to see, in anything but a very decayed state, the present triumphs of cartography. These remarks apply with special force to the " layered " maps; changes in the tones of the layers will greatly alter their character.

Topographical Maps. The following remarks are necessary to bring up to date the account of topographical maps given in 17.649. Such progress as has been made since 1910 was made chiefly before, or after, the war, and not during it.

United Kingdom. First in order of importance, the map on the scale of one inch to one mile is now no longer published in small sheets or in black with black hachures, or in brown with brown hachures. The " popular edition " now in progress supersedes the old " fully coloured " edition. This popular edition is printed in colours with brown contours and no hachures. The contours are