Sonrtas—On the Variolite and Associated Igneous Rocks. 103 
nicols, and somewhat resembles leucoxene. Frequently it occurs 
as long black threads strongly suggestive of trichites. 
In a great number of cases the nucleus of the variole is fur- 
nished by a lath-shaped crystal of felspar ; from the ends’ of this 
delicate rays, also of felspar, repeatedly branching diverge in regular 
curves towards the margin, leaving at the sides of the nucleus a 
SN 4 
Fic. 5.—Sheaf structure for spherulite. Ch. chlorite. 
space where but little structure is apparent. When fully deve- 
loped] the whole appearance of this beautiful growth forcibly re- 
ealls the distribution of lines of force about a bar magnet (figs. 4 
