OF ARTS AND SCIENCES. 



155 



Anrjlcs between Normals. 



Since * Dr. F. Becke's results of the determination of the same 

 crystals do not appear to be reconcilable with the above, a comparison 

 is important. The forms r (110) / (ITO) when referred to the crys- 

 tals which I have examined, correspond to {021}, and o (Til), u 

 (TTl) would, if present, occur as the prism {120}. Among the many 

 sets of crystals submitted to me I have never observed the prism 

 {120}. The following table shows a few of the angles both actual 

 and hypothetical, assuming that the crystals are monoclinic in form, 

 when compared with Becke's corresponding measurements. 



Monoclinic. 

 (010) A (021) = 44° 41' 

 (021)A(05l) = 90° 38' 

 (05I)A(0T0) = 44° 41' 

 (010)A(T20) = 47° 45f' 

 (T20) A (T^O) = 84° 28|' 

 (HO)A(OTO) =47° 45 1' 

 (010) A (021) = 44° 41' 

 (010) A (120) =47° 452-' 



Becke. 



The following measurements, which were obtained from a single 

 crystal, appear to establish conclusively the system of crystallization as 

 monoclinic. 



* Sitzungsberichte der kaiser. Akad. der Wissensch., Band Ixxxiii. 286-287, 

 Wien, 1881. 



