S. L. Penfield — Stereographic Projection. 



131 



25 



As pointed out on page 125 and shown in plate IY, 

 it. is an easy matter to shift a stereographic projection 

 so as to bring any desired point to 

 the center. Figure 25 shows the distri- 

 bution of some of the meridians and 

 parallels when the intersection of the 

 95th meridian and the 40th parallel is 

 brought to the center of the stereo- 

 graphic projection. The point 95° "W". 

 40° N. is about in the center of the 

 United States. The map is- not re- 

 duced, but shows the actual size of the United States as it 

 appears at the center of a stereographic projection, based upon 

 a circle of 14 cm diameter. The distance from right to left across 

 this map is 28 mm (1-J inches), and the distance from New York 



26 



to New Orleans is 10J mm , but little over f inch; yet in spite 

 of the very small scale on which the map is made, and also 

 of the fact that the United States is at the center of the hemi- 

 sphere where it appears the smallest, measurements can be 

 made with the stereographic protractors to within a fraction of 

 a degree. For example, New York to New Orleans was meas- 

 ured by protractor No. II, after making a reduction for shrink- 

 age, as 17° 8', calculated 16° 52', a difference of but 16', or 

 about 18 statute miles. 



There is but little distortion, due to the stereographic pro- 

 jection, provided a map does not cover an area larger than that 

 of the United States. Measuring from right to left across the 



