S. L. Penfield — Stereographic Project 



ion. 



Some essential features of the stereograpbic projection are 

 illustrated in figure 1. The circle represents a vertical section 



through a sphere, or a north and south meridian if considered 

 as such. N and S are the north and south poles, respectively, 

 and A B is the trace of the plane of the equator. Points on 



the meridian 20°, 45°, 70°, and 90° from N, when projected to 

 the south pole, are seen upon the plane of the equator at a, b> 



