470 



MEASUREMENTS OF CRYSTALS. 



CALCAREOUS SPAR. (Continued.) 



P one 135° 0' 0" 



P onm 149 2 11 



P onr orr' 151 2 40 



P ons 119 2 11 



c on r or c' on r ., 152 6 50 



g oni 112 10 



g ons 127 52 30 



jw on s or m' on s' .. 121 32 54 



m on s' or m' on s . . 154 39 13 



s ons 63 44 55 



s ons' 116 15 5 



t ont 137 39 26 



Fig. 83. A twin from Haverstraw, Rock- 

 land county. Angle of revolution 

 60°. 



CALCAREOUS SPAR. 



Fig. 89. A twin similar to that represented 

 in Fig. 79, but with the additional 

 planes t. 



Fig. 90. A twin from Haverstraw, Rock- 

 land county. Face of composition 

 parallel with a plane passing through 

 the vertical axis : angle of revolu- 

 tion 180°. 



Fig. 91. Two solid angles of the primary 

 rhombohedron replaced by tangent 

 planes. 



Figs. 92 and 93. Twins of the preceding. 



Fig. 94. A twin from Rossie, St. Law- 

 rence county. 



