428 ACCOUNT OF THE ARCTIC REGIONS. 



others are beautifully variegated, within the perime- 

 ter, by white lines, forming smaller hexagons or 

 other regular figures, in immense variety; Plate IX. 

 Fig. 25, 27, 28, 36 ; Plate X. Fig. 49, &c. The 

 size of this species is from the snlallest visible speck 

 to about one-tenth of an inch diameter. 



c. Aggregations of hexagons. This beautiful spe- 

 cies admits of immense variety. It occurs chiefly 

 at low temperatures, and presents great limits of di- 

 mensions ; Plate VIII. Figs. 2, 9, 10, 14, 17 ; and 

 Plate IX. Figs. 29, 34, 37, 39, &c. afford examples 

 of this species. 



d. Combinations of hexagons, with radii or 

 spines, and projecting angles. This constitutes the 

 most extensive species in the arrangement ; and af- 

 fords some of the most beautiful specimens. Fig. 7, 

 Plate VIII. is an elegant combination of spines and 

 hexagons ; and Figures 50, 55, 58, 59, 60, &c. 

 Plate X. together with all the others distinguished 

 by the letter s after the numbers, constitute a novel 

 and beautiful variety, which I have only once observ- 

 ed. The parallel lines that appear in these figures, 

 are not intended as shadings, but actually occurred in 

 the crystals, though with this difference, that the 

 lines which appear black in the plate, were all white 

 in the originals. Figures 56, 63, 64, and 93, were 

 opaque crystals, and were not so thin as the others. 



The latter of these, as well as Fig. 94, each having 

 twelve spines, appear to be accidental varieties, and 



