Stereographic and Gnomonio Projections. 



207 



18° 26'* ; in fact, even when drawn on quite a large scale, the 

 plan and parallel- perspective views, figures 2 and 3, are so 

 nearly identical with corresponding figures of axinite, page 73 

 of the writer's earlier paper just referred to, that the eye can 



Figures 1 to 5. Development of a plan and parallel- perspective figure of 

 axinite, triclinic system, from a stereographic projection. 



scarcely detect any difference between them, even when placed 

 one above the other. 



The easiest way to explain the construction of figure 3 from 

 figure 1 is to imagine the sphere, represented by the stereo- 

 graphic projection, as revolved 80° about an axis joining S 

 and 8', or until the great circle SES' becomes horizontal. 

 After such a revolution, the stereographic projection shown 



* This Journal (4), xix, p. 40, 1905. 



