REPORT OF THE DIRECTOR I9II 



187 



at the intersection of the zones [no. 211] and [100. 121], both of 

 which zones are well marked. The face 

 gave fair images of the signal, fell well 

 in the zones indicated and showed a close 

 agreement between measured and calcu- 

 lated angles in these zones. The form 

 was also found on two of the smaller 

 crystals measured. Four of the smaller 

 crystals referred to above were measured. 

 These were found to be of a slightly 

 different type as shown in figure 7, 

 which gives three projections of one 

 of these minute crystals. The fol- 

 lowing forms were observed: <:(ooi), b(oio), a(iio), /(310), 

 m(iio), 4(130), ^(oii), 3'(ioi), Willi), (^(112), /J.(i2i), 

 i?(i32), £(121), ^(211) and 1(321)*. 



The forms of this and the preceding types were identified by the 

 following measurements : 



Fig. 7 



LETTER 



ANGLE 



NO. 



MEASURED 



CALCULATED 



b :i 



010 



: 130 



3 



17° 35F 



ir 35' 



: m 





: no 



16 



43 32I 



43 33 



:/ 





• 130 



7 



70 37 



70 41 



c : e 



001 



. on 



2 



29 28 



29 33 



m : e 



no 



on 



2 



58 30I 



58 35^ 



c : b 



001 



031 



I 



59 36 



59 33 



y : u 



lOI 



in 



2 



24 14-1 



24 15 



b : u 



010 



III 



2 



65 43 



65 45 



(7 : (7' 



112 



112 



I 



28 45 



28 48 



m : <y' 



no 



112 



2 



81 37§ 



81 30I 



c : !J- 



001 



121 



I 



47 20 



47 23 



a : !^- 



100 



121 



2 



61 37 



61 2l| 



m : !J- 



no 



121 



3 



35 16 



35 23! 



c :R 



001 



132 



I 



43 50 



43 57 



m' :R 



no 



132 



2 



61 21 



61 25i 



c : £ 



001 . 



121 



I 



55 33 



55 38 



a' :e 



100 



121 



2 



79 37 



79 51^ 



b :e 



010 



121 



2 



41 28,^ 



41 21 



m' : £ 



no 



121 



2 



48 20 



48 17 



a' : r 



100 



211 



I 



54 4 



54 13 



b : ' 



010 : 



211 



3 



65 48 



65 41 



m : "^ 



no 



211 



3 



45 19 



45 28 



a' :l 



100 



321 



2 



47 48 



47 50 



b :l 



010 



321 



2 



55 40 



55 31 



m' : I 



no 



321 



2 



29 12^ 



29 19 



