Simpler Methods in Grystallograpliy. 



349 



outward from 0, marking the point where the one line cuts 

 the primitive in vii. and viii. as 101 {d), and its continuation 

 beyond as D in both quadrants. (See Fig. 3, in which the 

 axial lengths, however, are arbitrarily chosen.) 



58. I^ext, with a set-square, mark off on the inclined axis 

 in VI. and viii. the points where a right angle to that line 

 cuts c, above and below o, and sign the point with an italic 

 capital G in both quadrants ; also mark the point where the 

 inclined axis 0(7 cuts the primitive in both viii. and vi., and 

 sign them with a small italic c, which marks the position of 

 (001) on the circle of projection (see Fig. 3). 



59. In like manner, in quadrants v. and vii., draw per- 

 pendiculars from ox to A, and sign these points on ox with 

 a capital italic A^ and the point where this line cuts the 

 primitive a. This last marks the position of the pole (100) 

 on to the circle of projection. Draw a line parallel to ox at 

 any convenient distance outside the circle of projection, and 



produce it each way to touch either d. Figure that to the 

 right of c (6), and that to the left (7). Also draw lines from 

 either a parallel to oc to touch D, mark the one to the right 

 hand (5), and that to the left (8). It is along these lines 5, 

 6, 7, 8, that the positions of all the poles in the zone ca, front 

 and back (or positive and negative), are first measured in 



