150 Professor J. W. Gregory — 



feet.^ The date and mode of formation of that plain are imcertain ; 

 Ibut it was probably cut when the country was lower than at present, 

 and that plain may have been nearly at sea-level. 



The history of the existing valleys begins Avith the elevation of 

 this plain into a plateau. During the uplift radial streams must 

 have flowed from the granite highlands. There are in North Arran 

 about twenty-two radial streams in addition to the lower ends of 

 the major valleys. These radial streams trend as follows : — 



N.E. Two streams of North Glen Sannox. 



E.N.E. Glen Sannox. 



E. Four streams near Corrie, of which the longest is the White Water Glen. 



S.E. Merkland Burn and Gnocan Burn from Goatfell. 



S. The eastern Garbh Allt, from Ben Tarsuinn. 



S.S.W. The western Garbh Allt from Beinn Nuis ; and Auchencar Burn 



from S.S.W. of Beinn Tarsuinn. 

 S.W. Glen Scaftigill. 



W. Eight burns, of which the longest is the Allt Gobhlach. 

 N.W. Abhainn Beag. 



These radial streams are all of secondary importance. The 

 major valleys, in which ground less than 1,000 feet in height reaches 

 the centre of the granite mountains, run north and south. The 

 granite dome is, in fact, dissected by three main valleys which cut 

 across it north and south. The longest and most conspicuous of 

 these valleys is that of Glen lorsa and Glen Easan Biorach ; it cuts 

 across the middle of the granite mass. Further east is the valley 

 of Glen Eosa, which is continued northward by Glen Sannox ; this 

 joint valley runs north and south for most of its length, but both 

 its lower ends bend eastward to the sea. The third north and south 

 valley, that of Glen Catacol and Glen Scaftigill, is on the western 

 side of the island ; its lower end bends westward to the sea, which 

 the Scaftigill Burn reaches through the lorsa Water. Each of these 

 three valleys includes a large tract of ground below the level of 

 1,000 feet. On the floor of Glen lorsa a band of alluvium, most of 

 which is below the level of 250 feet, occurs in the very centre 

 of North Arran ; even the uppermost part of this alluvium is below 

 350 feet. Most of the floors of Glen Eosa and Glen Sannox are 

 less than 500 feet above the sea. 



In addition to the three north and south valleys there is another 

 major valley in North Arran. It consists of Glen Chalmadale and 

 North Glen Sannox ; it crosses the island from Loch Eanza east- 

 south-eastward to Sannox Bay and separates the plateau of Creag 

 Ghlass Laggan (1,453 feet) from the rest of the highlands. 



The valley system of North Arran may therefore be classified as 

 follows : — 



A. Minor Valleys. 



I. Radial valleys from the granite hills. 



B. Major Valleys. 



II. The three north to south valleys across the granite hills. 



^ This feature was recognized and illusti'ated by Sir A. C. Ramsay (1841, 

 sect, i, opposite p. 8). 



