OCCURRENCE IN ANCIENT BRITISH LAVAS. 169 



Discussion. 



Mr. EuTLEY bore testimony to the careful observations of the 

 author of the paper. The only cases in which he felt any doubt 

 were those in which the irregular form of the nodules did not seem 

 to be altogether reconcilable with their spherulitic origin. 



The President was not able entirely to agree with the author ; 

 for while his explanation might account for some of the structures, 

 yet many seemed to be due to an original vesicular character of 

 the lava. He adduced cases which he thought could only be 

 accounted for by the expansion of vapour-bubbles in a glassy rock, 

 disturbance of equilibrium being capable of inducing crystallization. 



The Author stated that he did not intend to apply his explana- 

 tion generally, but only to the cases he had examined. Some of the 

 irregularities in the form of the spherulites are due to crushing and 

 faulting of the rock in which they are enclosed. 



