1X8 : THE PYROMEEIDES OF BOULAY BAY (jeESEY), [Peb. 1898, 



DlSCUSSlON^. 



Dr. J. W. Geegory remarked on the resemblance between the 

 sections exhibited by the Author and the hollow spherulites of 

 Obsidian Cliff. He suggested that the infiltration of quartz into 

 such hollow spherulites, which often consist of concentric, separated 

 layers, would account for the formation of such pyromerides as 

 those of Jersey. He thought that the characters of the Obsidian 

 Cliff lithophyses could be best explained by the alteration of spheru- 

 lites through their inclusion in a lava of later date than their original 

 formation ; and he noted the coincidence of the occurrence of 

 brecciated obsidian in association with the lithophyses in the one 

 case, and of brecciated felsite in association with the pyromerides of 

 Jersey. He congratulated the Author on this interesting contri- 

 bution to the literature of the coarsely spherulitic rocks. 



Prof. JBoNNEY said that the Author had mentioned the obsidian 

 from the Yellowstone Park, but inclined to the view that those 

 spherulites were due to radial devitrification. At the same time it 

 would be quite possible that the structure described by Dr. Gregory 

 might also occur, for the Author considered the spherulites and 

 pyromerides of Boulay Bay to have had different origins. 



