232 I)E. IT. H. THOMAS OlS" XE]S"OLITHIC [vol. Ixxviii, 



List of Localities. 



1. Rudh' a'Chromain and Nuns' Pass, Carsaig. 



2. Bed of small stream, tributary to Abhuinn nan Torr, 1100 yards north 



of the cairn on Mullach Glac an t'Sneachda. 



3. Streamlet on the northern side of a plantation, 1 furlong north of 



Feorlein Cottage, Carsaig. 



4. Old Road, 100 yards north-west of Feorlein Cottage, Carsaig. 



5. Close to Beach River, 500 yards above the junction with Abhuinn an 



Easa' Mhoir, 



6. Coast, 1165 yards slightly north of west of Ormsaig. 



7. 2600 feet east-south-east, and 1850 feet south-east by south of 



Kilpatrick. 



8. 2560 feet north-north-east by north of the northern end of Eilean Ban. 



9. 1980 feet north of west of Ardchrishnish. 



10. 1150 feet east-north-east of Lochan a'Phuill. 



11. 55 and 85 yards north-east of the north-eastern end of Traigh Bhan an 



Sgoir. 



12. Shore, a quarter of a mile south-west from the mouth of Allt na Coille 



Moire. 

 13 & 15. Allt a'Mhuchaidh, 100 yards above the bridge. 

 14. 400 yards south of Seabank Villa. 



16. Abhuinn Bail' a'Mhnilinn, 100 to 200 yards above the bridge. 



17. 700 yards south-west of Tiroran. 



To the foregoing list could be added man}'- other localities within 

 the same region, but those enumerated afford thoroughly repre- 

 sentative examples, and will be found sufficient for investigators 

 who wish to study these intrusions in the lield. Further, it is from 

 these localities that the bulk of the xenolithic material has been 

 collected ; and, in order to guide future workers, they have been 

 indicated on the appended small-scale map (fig. 1, p. 230)^ under 

 their respective numbers. 



An excellent and fully exposed example of the xenolithic intru- 

 sions is the composite sill that forms the low promontory of E,udh' 

 a'Chromain, west of Carsaig (Locality 1) : here the components of 

 the sill can be studied in detail, and their relative ages demonstrated. 

 Further, the relation of the sill as a whole to the rocks into which 

 it has been intruded is particularly clear, and the occurrence is 

 easily located. For these reasons this sill may be taken as the 

 type with which to compare the other xenolithic intrusions, and its 

 petrography will be described in some detail. 



It consists of an acid central member, 20 to 30 feet thick, which 

 is bounded on each side by lateral basic members of less, but 

 unequal, thickness. It may be traced across the foreshore and the 

 raised-beach platform to the cliff below Nuns' Pass, where it is 

 either faulted or rapidly cuts across the Tertiary lavas, to a position 

 in the cliff about 100 feet above sea-level. 



On the west its basic lower portion is in contact with the 

 Carsaig Sandstone (Jurassic); but on the east the upper basic 



^ A sketch-map showing the two original localities for sapphire-bearing 

 xenoliths was reproduced in the ' Summary of Progress for 1912 ' Mem. GeoL 

 Surv. 1913, p. 48. 



