MAP MAKING IN THE FIELD. 65 



identify the relief with its contours. When this is mas- 

 tered a good contour map will be almost as graphic as a 

 miniature model of the country. 



In sketching contours it is of great assistance to 

 imagine the sea level raised. Thus, if the 5,000-foot 

 contour is being sketched, we may imagine that the 

 salt waters of the earth are raised 5,000 feet higher than 

 they now are. It is evident that the true contour 

 would follow the shore line which is thus imagined and 

 that bays and harbors, islands, straits, etc., would 

 result. It is evident that contour lines can not cross 

 each other or themselves and that they must connect 

 somewhere, either on the map which is being prepared 

 or in some other region. 



The contour map, when thus prepared, is only a base 

 map for other data to be collected for the Forest Service. 

 Some of this data may be collected as the survey pro- 

 ceeds, such as the classification of the land, timber, 

 woodland, barren, etc., or the composition and stand of 

 a forest. When the plane-table map is being made in 

 the field, the paper is necessarily covered with pencil 

 notes and lines which give the names of points, eleva- 

 tions, directions, etc. There is no need to encumber this 

 map with other figures or names which may be confus- 

 ing or lead to error. A better plan is to cover the map 

 with a piece of tracing cloth, with the dull side up, 

 which may be thumb-tacked along one side only, that 

 it may hang back out of the way when work is being 

 done on the base map. On this the burns, windfalls, 

 barren areas, or stand may be sketched either in black 

 or with colored crayons without smearing the base 



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