Geographical Maps and Sailing Charts. 



271 



other the antipodal point P. The plane upon which the map 

 is drawn is at right angles to a diameter running from 40° N., 

 95° W., to P. By reference to an atlas it will be seen that the 

 point where the flag is located, 40° N., 95° W., is near the 

 center of the United States. The model is admirably repre- 

 sented by the figure, and no further description seems neces- 

 sary. 



Figure 17 is a projection upon the plane of the horizon at 

 40° N., 75° W., very near to New York City. The projection 

 of the parallels and meridians is the same as shown on the 



18 



JO 20 



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1 1 f 



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map in figure 16, but the meridians are numbered differently. 

 The parallel 40° S. is a straight line on the map, and why it is 

 thus represented is at once apparent from consideration of 

 figure 16. 



The principle of making a map on a plane tangent at any 

 given point is not so important for the projection of hemi- 

 spheres as for the mapping of limited areas, and in order to 

 appreciate the advantages of this method of map-making it 

 will be necessary to consider more carefully the character of the 

 distortion near the center of a stereographic projection. 



Distortion resulting from the Stereographic Projection. — 

 Figure 18 is a graphical method of representing the distortion. 

 Let the divided circle represent any meridian with as the 



