AXIAL KLKMKNTS. 



45 



reading on 6(010) was averaged for each crystal from the readings 

 obtained on (010) and (OlO) (often a cleavage face), and from the aver- 

 age of (110) and (UO), and (210) and (2lO), respectively. The c(001) 

 fmvs were generally striated in the zone (001) : (100), but this in 

 nowise interfered with the accuracy of the measurement of the angle 

 (001) : (Oil). The accurate measurements from (001) to (102) and 

 to (100) were very few in number, as the base (001) was striated in 

 this direction on most of the crystals. 



COMPARISON OP VALUES. 



Instead of deriving axial elements from these angular values I 

 have compared the interfacial angles directly with the best ones 

 I could find hi the literature for the entire wolframite group. These 

 have been arranged in order of decreasing percentage of MnO, so 

 that the first lines in the table below represent hiibnerite and 

 the last lines (except the very last) represent ferberite. The very 

 last line contains the values taken from Goldschmidt's Winkel- 

 tabellen, in which the axial elements of Descloizeaux, Krenner, 

 and Seligmann have been averaged. (See Bibliography, pp. 74-75.) 

 A careful study of the angular values given in any column 

 does not show any regular increase or decrease corresponding 

 with the regular decrease in percentage of MnO. In fact the varia- 

 tion in angular values for two or more wolframites of nearly the same 

 composition is nearly as great as between the extreme end members. 

 The correlation of the chemical composition and the crystallographic 

 constants is doubtful in so far as the analytical figures given were 

 not obtained on the material actually measured. 



Comparison of angles with variation in chemical composition. 



o Computed from axial elements of Descloizeaux, Krenner, and Seligmann. 



