Watanabe — Babingtonite from Japan. 161 



crystal faces are often striated and curved, and the 

 appearance of double and multiple images makes it 

 doubtful which is to be measured. In spite of such diffi- 

 culties in measuring, the mean values obtained by 

 measurement closely agree with the calculated ones. 



The observed forms and their co-ordinate angles are 

 shown in Table I. 



The four forms marked with an asterisk are new to this 

 mineral. The crystal orientation and elements, used for- 

 notation and calculation, are those of Dauber, 6 the advan- 

 tage of which has been stated by Palache and Fraprie. 7 

 It is necessary, therefore, to change the symbols of forms, 

 when these results are compared with the descriptions, 

 which are found in the treatises of Dana and Hintze, or 

 with those of Goldschmidt, 



The calculated and measured angles of the forms in 

 the vertical zone agree closely; but with regard to the 

 terminal faces, the deviation of the measured values from 

 the calculated ones is often great. This is partly due to 

 the general disadvantage of a theodolite goniometer that 

 the possible error by measurement of the meridional 

 angle 4> increases as the polar distance p diminishes. To 

 compensate this deficiency, the interfacial angles between 

 the faces belonging to the zone (be) were measured by 

 using the theodolite goniometer as a one-circle one. The 

 results of these measurements fairly well coincide with 

 the calculated values as shown in Table II. 



Table II. 



Measured. 

 Calculated. (mean). 



be 92° 36' 92° 29' 



be' 87° 24 87 32 



bs 44 40 44 08 



cs ..-'.... 42 44 43 07 



co 45 13 45 22 



bo 47 23 47 25 



6 The crystal elements of babingtonite, given by Dauber (Pogg. Ann., 94, 

 402, 1855) are as follows: 



a : b : c = 1.635 : 1 r 0.8955; a = 86° 09', p = 93° 48', y — 112° 22'. 

 ab — 67° 48', ac = 87° 28', be — 92° 36'. 



These values were obtained by him from the results of measurements on 

 more than eighty crystals of babingtonite- from Arendal. 



7 Palache and Fraprie, Proc. Amer. Acad., 38, 382, 1902. Some misprints 

 occur in their table of corresponding forms for the different positions. 



