SOME CALCITE CRYSTALS WITH NEW FORMS 1 3 



crystal was set in polar position by means of the e faces and the 

 other forms gave the following measurements: 



fiOlll!. p calc. = 44° 36' meas. 47° 53' 



" 45 45 



42° -45° 



All faces gave a mass of signals. 



!rJ0.17.17.l! p calc. = 86°35' meas. 87°07' 



86 12 

 86 45 

 86 16 

 86 30 

 86 approx. 



All faces gave merely a mass of brightness and the angles measured repre- 

 sent the center of this mass. 



S:|11.8.19.3|,calc. </. = 24°48' p = 79°34' 



meas. = 25 15 = 78 42 

 meas. 25 35 78 05 



tjl7.16.33.l|calc. <^ = 28° 59' p = 87° 58' 



meas. = 29 27 = 88 08 



meas. = 28 41 87 51 



meas. = 29 21 87 21 



meas. = 28 26 87 28 



The agreement is only approximate, but the faces were so poor that 

 only two out of the six could be even approximately measured. 



Here again the symbol is only an approximate one. If we change 

 the orientation of the crystal to that given by Goldschmidt in his Win- 

 keltabellen the indices of this last form become (49.1.50.1) and_it is 

 not possible to say whether they should not be, for instance, (50.1.51.1), 

 etc. Even in the orientation here taken, the average of the four meas- 

 ured angles agrees well for a number of forms. 



Av. of 4 meas. angles = 28° 59' = 87° 42' 



Calc. for 17.16.33.1 28 59 87 58 



Calc. for 16.15.31.1 28 56 87 50 



Calc. for 15.14.29.1 28 52 87 41 



However, while the correct indices could not be determined, we have 

 here a form with indices near to one of those given above and still too 

 far removed from the prism a 1 1120 | to be referred to that form. 

 The writer could find no form for calcite approximating to those just 



