ly Means of Graphical Methods. 



279 



and G axes. In order not to complicate figure 27 to too great 

 an extent, the solutions depending upon plane trigonometry 

 were worked out on a second divided circle, shown in figure 28. 

 Having located the poles a, 100, and c, 001, the vertical and 

 clino axes are represented by diameters at 90° from them, as 

 indicated by broken-dashed lines ; the lower half of the verti- 

 cal diameter, liowever, may be employed for plotting the rela- 

 tions of the b axis, the length of which is unity. Referring to 

 figure 27, the angles t: and r (compare figures 6 and 8) were 

 measured, respectively, by the stereographic scale as 4l° 20' 

 and 40° 20', and these inclinations plotted from a and <?, figure 

 28, determine the lengths of the c and a axes, which were 



found to be as follows: c = 0*880 and <3^= 0*850, calculated, 

 (?=0'880 and (X-^ 0-850. In order to determine the relations of 

 the prisms m and w, through unity on the a axis, a line was 

 drawn at right angles to the radius through in and vj^ thus fix- 

 ing a base-line Ox • then from x the inclinations of 7)1 and w 

 (the p angles), 19° 39' and 30° 29', are plotted, and, as shown 

 in figure 28, they intercept the lower radius at unity and one- 

 half , respectively. Since the lower radius is taken to represent 

 the h axis, the axial relation of r)i is a : h : ooc, and of ^^, <^ : 

 •J5 : ccc, the indices being 110 and 120. I^aturally the reverse 

 of this method may be employed to advantage for determin- 

 ing the length of the a axis in this system, when the inclina- 

 tion /? and the prismatic angle are given. For determining 

 the symbol of a clinodome, for example s / through unity on 

 the G axis draw a line at right angles to the radius through s, 



