PALACHE. — CRYSTALLOGRAPHY OF LEADHILLITE. 455 



many of the forms first found on the Utah leadhillite, and particularly 

 of the best established ones. Ten of the Utah forms regarded as 

 certain and five of those considered doubtful were found on the Nevada 

 material, furnishing a welcome confirmation of the results recorded in 

 the preceding paper. Moreover, the thirteen Utah forms not observed 

 here were with one exception weak or uncertain forms. 



Only two of the forms known on leadhillite previous to this investi- 

 gation were not observed. The first of these, o- (233), was first 

 found by Artini as a minute face ; he could obtain no measurements 

 and regarded it as doubtful. One face was found on a crystal from 

 Utah near this position, and the form is probably to be regarded as 

 established. 



The second form, t (?. 14. 7), with complex symbol and abnormal 

 position in the form system of leadhillite, is a dubious form, probably to 

 be replaced by the simpler form (T42), which is not far removed. This 

 possibility was, however, considered by Artini and rejected. He ob- 

 served a single face of the form, the observed zonal relations and 

 angles of which seemed to him to preclude its interpretation as (142). 



The combinations observed are shown in Table IV. As was the case 

 with the Utah crystals, the forms most frequently found are c, a, m, 

 and r, which are present on nearly every crystal, b, d, 1, g, <£, u, w, k, 

 x, q, and v are present on at least half the crystals. Of the remaining 

 forms the new prism, j, and the pyramids A, n, y, and p are the most 

 important, all others being of very rare occurrence. 



The new forms on the leadhillite from Nevada, with which will be 

 included the five uncertain Utah forms here confirmed, are based on 

 the following data : 



j, 4 oo (410). A prism, well established by frequent occurrence 

 with distinct faces, often of good quality. 



X, 0£ (013). Seen twice as a distinct face in the clinodome zone. 

 Reflections poor. Found also on the Utah leadhillite, and hence re- 

 garded as assured. 



