NEW FORMS. 



49 



On crystal 1 the new pi ism was noted once with the forms a {100}, 

 w{l 10}, 6(010} . On crystal 22 the portion of the zone with the new 

 prism was richer in faces, chose present being 6(010), ra(TlO), Z(2lO), 

 7^(520), a(TOO). The new form F is considered as established, 

 though the agreement between the angles is not so good as for the 

 two more complex symbols just described. 



Measurement of *C?{720}. 



(calculated 

 76 44'). 



Crystal No. 14 76 4S 7 



The new prism was observed only once as a narrow face yielding 

 a fair reflection. It formed one of four faces lying very close together, 

 pach of which, however, gave a distinct signal. These four faces, 

 lying between m(110) and a(100), are #(720), a face near (410) but 

 not determinable, 3/(510). and #(11.2.0). 



Measurements of *J/{510}. 



The new prism M is always associated with several other rare 

 prisms. Narrow faces of it were found on crystal 13 with n(810), 

 a(100), n(8TO), M(5lO); on crystal 1 as a striated face with 6(010), 

 m(110), F(520), a(100), Jf(5lO), Z(2lO), m(UO), and 6(OTO); and on 

 crystal 14 with #(720). 



Measurements of *JV{ 11.2.0 /. 



The two faces of N on crystal 14 are both narrow and both occurred 

 with other prisms, but each with different forms. With one of them 

 the associated forms were m(TlO), #(720), a face near (410), if ($10), 

 #(11.2.0) and cr(TOO); with the other the forms were n(STO), Z(7IO), 

 and #(IT.2.0). On crystal 17 TV occurred with a (100), n(810), and 

 Z(210), being broader than either Z or n. 

 35659 Bull. 58314 4 



