446 LITHOPHYSES IN THE OBSIDIAN OF THE KOCCHE EOSSE. 



Mr. J. W. Gregory remarked on the close analogy between these 

 Rocche E-osse lithophyses and those of the Obsidian Cliff. He 

 quoted several facts which showed that many of the latter must 

 have been formed prior to the consolidation of the rock, and were 

 thus of a different origin from those of Eipari. 



Mr. Rftlet, while acknowledging the interesting nature of the 

 views advanced by the Authors, wished to know how the original 

 boundaries of the vesicles could be accurately determined. If, 

 instead of the walls of vesicles, there were merely cracks in the 

 vitreous mass, crystallization would then occur upon both sides of 

 the fissure, but in the case of a vesicle, unless fresh matter were 

 introduced, he failed to see from what source the material of the 

 crystalline fibres lying within the vesicle was derived, except from 

 the wall of the vesicle itself, in which case it would be difficult to 

 fix its original boundary. 



Prof. Cole stated, in reply, that hollows might occur by decay of 

 spherulites although the glass around remained remarkably fresh, 

 the fibrous and other structures in the crystalline materials rendering 

 them more open to attack. Only ' spherulites ' with the dual type 

 of structure described could be claimed as of lithophysal origin, the 

 great bulk of spherulites in other areas, with or without concentric 

 structure, being formed by outward growth from a central point. 

 The curvature of the outer surface of the mushroom-like bodies was 

 independent of that of the vesicle on which they originated. 



Mr. G. W. BrTLER explained that, in judging as to the original 

 boundary of the vesicles, the Authors had been mainly guided by the 

 flow-lines of the original glass, which can be traced through part, 

 but not all, of the crystalline material. 



