PLATE I. 

 JUNCTION OF GRANITE AND SILURIAN ROOK, GLEN RIVER, NEWCASTLE, CO. DOWN. 



To the left a lamprophyre dyke, cut off by the granite. G— Granite; S— Silurian shale; 

 D— Dyke of Dioritic lamprophyre. (From a photograph by Miss M. K. Andrews : copyright). 



