Mr. L. Fletcher's Cry stallographic Notes. 189 



obtained by the method of maximum illumination: — 



Observed. Calculated. 



010.131 . . 59° 0' 59°24' 



010.141 . . 51 45 51 45 



In four crystals (0 2 1) occurs at the same time as (0 1 1), 

 whilst in two crystals (1 1 0) and (0 1 1) occur together: 

 (2 5 2) was met with on three crystals, (3 4 3) on two, (1 2 1), 

 (1 1 1) on one and the same, (1 3 1), (1 4 1) each on a single 

 crystal. We therefore must agree with Schrauf that the domes 

 appear to show a different development of planes; but still 

 we can give no rule by which one dome may be distinguished 

 from the other. 



VII. Realgar. 

 Forms already described as occurring on realgar: — 

 (100) (010) (001) (101) (201) (012) (011) 

 (032) (230) (110) (430) (210) (520) (212) 

 (111) (2 3 2) (412) (612) (4 21) (212). 



To these Scacchi adds* (1 2 0), (4 1 0), (2 1 4), (2 1 4). Hes- 

 senbergf confirms the forms (1 2 0), (4 1 0), and adds further 

 the forms (1 1), (6 1 0), (2 1 1), (6 7 0), (2 2 1). To the 

 above Dana, in his list of observed forms, adds (4 1 4), while 

 he omits (6 7 0). Groth, in his Catalogue of the Strassburg 

 collection, confirms the existence of the form (6 7 0), and adds 

 (4 3 2), considering that Hessenberg's (2 2 1) was in reality 

 this same form. 



To these may be added (3 2 0), (310), (6 5 0), (0 34), 

 (1 1 2), (6 1 6), (1 5 1 1 5): the plane (4 1 4) given by Dana 

 has also been observed. The unconfirmed form (2 1 4) of 

 Scacchi has been met with largely developed. The forms 

 (5 2 0), (2 1 4), (1 1), (6 1 0), (2 1 1), (6 7 0), (2 2 1), (4 3 2) 

 have not been met with on crystals of this collection. 



A specimen from the Solfatara near Naples presents some 

 small crystals of realgar in a scoriaceous mass. Three crys- 

 tals were measured : the first presented the above-mentioned 

 forms (2 14), (414) in combination with old forms ; the 

 second showed the rich combination 



(010) (230) (110) (650) (430) (320) (210) 

 (410) (100) (032) (011) (012) (001) (232) 

 (111) (212) (101) (412) (2 01) (2 12). 



* Liebig and Kopp's Jahresberichte, 1852, p. 844, 

 t Hessenberg, Mm. Notiz. i. and iii. 



Phil Mag. S. 5. Vol. 9. No. 55. March 1880. P 



