274 Penfield — Use of the Stereographic Projection ft 



or 



constructed. Having fixed the center of the hemisphere, the 

 intersections of the several parallels with the central meridian, 

 N"S", may be projected down from the elevation above, and 

 to find the center points and construct the circles which repre- 

 sent the projection of the parallels on the map scarcely needs 



20 



Illustration of the principles upon which a stereographic map of a limited 

 area is constructed. 



explanation. When drawing a map on a large scale the several 

 intersections of the parallels with the central meridian, and the 

 lengths of the radii for describing the parallels, are determined 

 by calculation, making use of a table which will be explained 

 at the conclusion of this article. To construct the meridians, 

 the following principles are made use of : The} 7 are circular 

 arcs passing through the stereographically projected north and 

 south poles, N" and S" , and their centers must be on the line 



