560 SPHEEOID-BEA.KING GKANITE OF ITULLAGHDEEG, CO. DOITEGAI,. 



sort. The concentric concretionary structure is not confined to 

 melted rocks. He referred to certain slates in the Lake District in 

 which such a structure occurs. In the case of these spheroids a 

 molecular movement had taken place, showing that a certain amount 

 of plasticity had been retained in a rock which had never been in 

 a fluid condition. 



Dr. Hicks suggested that the proximity of intrusive rocks might 

 have set up some action of this kind by the production of cavities ;: 

 that the spheroids may therefore be considered as of secretionary 

 rather than of concretionary origin. 



Prof. Junn remarked that this was the first occasion in which 

 both radial and concentric structure had been found in any 

 spheroids in granite in the British Islands. The Society was to be- 

 congratulated on these specimens having fallen into such good hands, 

 and being so admirably described. He asked if the microperthitic 

 structure occurred in the felspars of the granite, and not in those of 

 the nodules. 



The Atjthoe observed, with regard to the suggestions of Dr. Hicks, 

 that the spheroids occur in a very small compass, and probably bore 

 no relation to the dyke. The minerals were not secondary pro- 

 ducts. Prof. Judd was quite correct in supposing that there was 

 microperthitic structure in the granite, but none in the spheroid. 



