Sottas—On the Variolite and Associated Igneous Rocks. 101 
specimens as little rounded bodies ranging in size from that of a 
pea downwards (Mr. Watts has since found examples half-an- 
inch in diameter) ; they are sometimes red, but more usually green 
in colour and weather to an opaque white powder. Under the 
Fig. 2. 
microscope the streaked appearance of the rock is seen to be due 
to irregularly alternating bands of different colour and compost- 
tion. Some are clearly divitrified glass traversed by numerous 
wavy lines of opaque white material giving it a fluxional appear- 
ance; others are similar, but in addition crowded with spherulites, 
singly and in groups, while others again are wholly spherulitic, 
the spherules in this case being more or less devoid of well-defined 
edges (fig. 3). Superposed upon these structures are crystals of 
epidote and zoisite collected in bands; these have been developed 
without completely destroying the structure of the glass, so that 
