lO 



SCHALLER 



q I 2.16.18.1 } of which the latter is doubtful, 

 are given in the following table: 



The angular values 



The large faces of 0| 8.2.10.3} are dull and give no distinct 

 signal, only a blaze of light. Two faces were measured with the fol- 

 lowing result: 



calc. (j> = 10° 64' 

 meas. (1) = 10 21 

 meas. (2) = 10 36 



p = 71° 38' 

 meas. (1) = 71 07 

 meas. (2) = 70 48 



Although the faces are dull and give no distinct reflections, the meas- 

 urements serve to fix the indices and as the form occurs in large 

 plane faces it is considered as well established. The corresponding 

 negative scalenohedron .S { 2.8.10.3 | has been noted a number of 

 times. Measurements for the form o {0.14.14.17 j are as follows, 

 the faces being bright and giving fairly good reflections. 

 The angles between the three faces of this form and e were measured. 



0.14.14.17 : 0112 



12° 52 - 12° 53' p= 39° 07' - 39° 08' 



12 44 - 12 45 = 38 59 - 39 00 



12 43 - 12 44 = 38 58 - 38 59 



Average (^) = 39° 02' 



limits, 38°58' - 39° 08' 



The only form for which the angle agrees is the complex one 

 {0.14.14.17}. Two simple ones which approximate to {0.14.14.17} 

 are given in the table below, but as can be seen neither one is sufl5- 

 ciently close to the measured values. 



calc. for {0556}, = 39° 25' 



calc.for {0.9.9.11} = 38 54 



