130 



THE NATIONAL GEOGRAPHIC MAGAZINE 



shading is to be used to bring out those 

 minor features which cannot be ade- 

 quately represented by contours. 



The map up to this point will comprise 

 the representation of streams and all 

 water bodies, of towns, railroads, and 

 highways, of political boundaries, of the 

 topographic relief, and the names per- 

 taining to all these features. It will be 

 what may be called a base map, adequate 

 in itself for all ordinary uses of the stu- 

 dent and traveler, but capable of receiv- 

 ing additional data which convert it to a 

 special purpose. In connection with our 

 census, it might be used to express 

 density of population by overprinting 

 different shades of color. Similarly, it 

 might be used as a crop map, a weather 

 map, or a geological map, or to bring out 

 the relations between lines of transpor- 

 tation or works of internal improvement, 

 whether national, state, or private. Thus 

 this base map contains in itself and in its 

 adaptability to a large number of special 

 purposes the highest practicable possi- 

 iDilities for usefulness. 



The conference in London, having had 

 its origin among geographers, felt con- 

 strained to emphasize the geographic 

 side of cartography, and particularly the 

 representation of altitudes of continents 

 and mountains with reference to sea- 

 level. These relations are indeed ade- 

 quately expressed by contours, if one ex- 

 amines the map with sufficient care, but 

 it is desirable, especially upon a general 

 map of large scope and moderate scale, 

 to bring the distribution of altitudes 

 more strinkingly into view. To that end 

 the conference adopted a scale of colors, 

 which should be printed on different por- 

 tions of the map, according to the height 

 above sea. The depths of seas and lakes 

 shall be shown by shades of blue ; the 

 lower lands, from the coast to 300 me- 

 ters (984 feet), by three tints of green, 

 shading into pale buff, which at 500 me- 

 ters passes into light browns, that grow 

 darker up to 3,000 meters. Above 3,000 

 meters the brown tints tone into rosy 

 violet, and fade away to white in the 

 highest summits bevond 7.000 meters. 



As applied to the United States, the 



effect of this color scheme will be to ex- 

 hibit light tints of green and buff" over 

 the Atlantic slope and throughout the 

 Mississippi Valley, and from their ex- 

 panse the Appalachian Mountains will 

 stand out in tones of brown. Similar 

 brown tints will indicate the rising plains 

 between the Mississippi A'alley and Colo- 

 rado, while the summits of the Rockies 

 and of the Cordillera will carry the violet 

 notes of high altitude. On the Pacific 

 slope the bands of color will be closely 

 crowded, bringing out at once the grada- 

 tions in tint and the relatively rapid rise 

 from the sea to the mountain crests. 



the; atlas Wlhh CONTAIN ABOUT I,500' 



she;e;ts 



The arrangement of sheets of the one- 

 millionth map is shown for the northern 

 hemisphere on page 131. It will be no- 

 ticed that each sheet measures 4 degrees 

 of latitude by 6 degrees of longitude. 

 Thus 60 sheets belt the earth and 22;^ 

 sheets extend from the equator to the 

 pole. In the discussions of the confer- 

 ence the execution of the circular sheet 

 covering the northern polar regions 

 within the parallel of 88 degrees was 

 courteously committed to the United 

 States. To represent an entire hemi- 

 sphere would thus require 1,321 sheets, 

 and for the entire Avorld twice that num- 

 ber ; but since three- fourths of the earth's 

 surface is ocean, the atlas will probably 

 never comprise more than 1,500 sheets, 

 including the oceanic islands. These 

 sheets are so designed that they may be 

 fitted together, without appreciable gaps, 

 to any number that may reasonably be 

 placed upon a single wall, and since they 

 will be executed through international 

 cooperation, without reference to na- 

 tional boundaries, according to a uni- 

 form style and method, they will really 

 constitute a single great map of the 

 world. 



THE MAP SHEETS OE THE UNITED STATES. 



The sheets which fall upon the area 

 of the United States, including parts of 

 the adjacent oceans and of Canada and 

 Mexico, but excluding Alaska, are 52 in 



