270 Penfield — Use of the Stereographic Projection for 



that a map may be made on a plane tangent at any desired 

 point on a sphere, or a plane parallel thereto at the center ; 

 and the results are equally satisfactory no matter where the 

 point of tangency may be. As will be shown, the object of 

 making this kind of a map is that any desired region may be 

 projected at the center of a hemisphere, where distortion is 



17 



Stereographic Map of a Hemisphere upon the plane of the horizon at 40° N. 

 75° W., near New York City. 



least, and where, consequently, a country may be mapped with 

 the best results. Figure 16 represents a model for demonstrat- 

 ing this kind of projection. The skeleton sphere is orientated 

 with the J¥. S. pole vertical, and the meridians and parallels 

 of the upper, front hemisphere are spaced 20° apart. The 

 equator is easily recognized, and it is important to keep in 

 mind two points, one, indicated by a flag, on the parallel 40° N. 

 where it would be intersected by the meridian 95° W., the 



