182 Mr. L. Fletcher's Crystallograpldc Notes. 



Observed. Calculated. 



110.310 .. 26 5 26 34 



100.310 . . 18 50 18 26 



101.013 . . 47 40 47 52 



Other crystals on this specimen have quite a different habit, 

 and present a symmetrical development of the combination 

 (100) (110) (111) (411), the faces of the cube being 

 predominant, as shown in fig. 1 : — 



Observed. Calculated. 



111.411 . . 34 45 35 16 



110.411 . . 33 5 33 33 



Several specimens from Lake Superior present forms pre- 

 viously unobserved. The first we shall mention is a parallel 

 aggregation of cubes : on some of the crystals the faces of a 

 tetrakishexahedron are developed. The indices of this form 

 were found to be (4 1 0) : — 



Observed. Calculated. 



100.410 . . 14° V 14° 2' 



In this case images were obtained. 



The second is a fine tetrakishexahedron, almost an inch in 

 diameter and very symmetrically developed; the form proved 

 to be (5 3 0):— 



Observed. Calculated. 



530-530 . 



. 62 45 



61 56 



530.350 . 



. 27 15 



28 4 



350.053 . 



. 42 45 



42 40 



Blurred images were obtained with this crystal. 



The same simple form is shown by a crystal projecting from 

 some massive copper and associated with laumontite and cal- 

 cite. The angles were measured with the hand-goniometer : — 





Observed. 



Calculated. 



530.530 . 

 350.053 . 



o 



. . 60 

 . . 44 



61 56 

 42 40 



The same form (5 3 0), but in combination with the cube, 

 is shown by a fourth specimen from Lake Superior. The 

 angles were measured with the hand-goniometer : — 



Observed. Calculated. 



530.530 . . 63°i 61° 56 



530.350 . . 27 28 4 



