CHAI'. XLVII 
THE GRANITE OF ARRAN 
419 
period are certainly known in Britain save those of Tertiary age. The larger 
hod} ot granite in the northern half of the island nowhere comes into direct 
contact with the newer red sandstones, but these strata are pierced by smaller 
bodies of granite. Hence, both by the evidence of their internal structure and 
by the stratigraphy of the ground, the later igneous rocks of Arran may be 
reasonably grouped together as one important and consecutive series, com- 
2 P 
parable in age and general characters with those of Tertiary date in the 
Inner Hebrides. 
The igneous rocks of Arran, later than the probably Permian sand- 
stones, range from acid to basic in composition. Besides the northern 
granite, there are in the southern part of the island acid rocks that 
indude granite, coarse-grained quartz -porphyry and fine-grained felsite. 
heie the relations of these rocks to each other can be seen, the felsite 
