Dec, 1908. Mineralogical Notes 151 



reflecting goniometer. Probably the most remarkable feature ex- 

 hibited by the crystals is their apparently hemimorphic develop- 

 ment. This development is shown in Figs. 3 and 4, PI. LI. Thus 

 the crystal shown in Fig. 3, PI. LI, exhibits at one end a small basal 

 plane with several modifying pyramids, while at the opposite end 

 the basal plane alone occurs. Again, the crystal shown in Fig. 4, 

 PI. LI, shows one end considerably modified by pyramids, while the 

 other possesses no modifying planes whatever. Such crystals might 

 be expected to show pyro-electricity but careful tests for this property 

 made with the kindly assistance of Prof. R. A. Millikan, of the Uni- 

 versity of Chicago, gave no indications of its presence. The apparent 

 hemimorphism is perhaps therefore to be regarded as due to distortion 

 only. Other interesting illustrations of distortion or merohedrism 

 are shown by the crystals. Thus on the crystal shown in Fig. 3, PI. 

 LI, but a single plane of the pyramid v (117) occurs, while the other 

 forms are present in normal number. The crystal shown in Fig. 4, 

 PI. LI, exhibits two planes of the pyramid v (117) and two planes of 

 the pyramid r (115). In addition occur two planes only of the dite- 

 tragonal pyramid s t (5.1. 19). On the crystal shown in Fig. 2, PI. LI, 

 a single plane of the pyramid of the second order G (104) occurs and 

 a pyramid new to octahedrite, M (338) is present as two planes, while 

 the development of the other pyramids is normal in character. No 

 differentiation of the planes in luster or etching figures can be noted 

 except that the pyramid of the second order G (104) shows numerous 

 pittings. In addition the dominant pyramid p (in) is always charac- 

 terized by striations parallel to the base. The total forms observed 

 with angles follow, the one marked with an asterisk being new. The 

 letter G has been given to the form 104, this form having been listed 

 by Hintze* but not lettered: 



s x (5- i- 19) 



