THE TUMMEL 75 



line will be seen to be that of Glen Garry and the lower Tumme 

 to the Tay at Ballinluig the line traversed by the Highland 

 Railway. The direction of this central line is rather singular, 

 being south-east, for the main axis of the mountains is at 

 right angles to it. The composition of the hills plus the glacial 

 erosion are no doubt responsible for the existing conditions, the 

 rocks of the region being of very different consistency and 

 capable of resisting the action of ice or of water to very different 

 extents. The erosion of the Loch Tay and Glen Dochart area 

 is more advanced, however, than that of the Tummel or Garry, 

 and the main line of the Grampians cuts off Loch Ericht from 

 the source of the Garry, and still forms a high and hard ridge. 

 The Tummel, and to a greater extent the Dochart and Loch 

 Tay, secure much greater length by having been forced, as it 

 were, to flow towards the central line from a west and south- 

 west direction. 



The direction of the Tummel is to the east throughout almost 

 its whole course. It rises from a number of small lochs lying 

 in glacial moraines in the Black Mount, south-west of the 

 Moor of Rannoch, and not far from the head waters of the 

 Orchy. The furthest back source is the stream called the Ba, 

 which rises about 3 miles west of the road from Loch Tulla 

 to Kingshouse at the head of Glen Coe, and flows into Loch 

 Ba, thence into Loch Laidon, and so on to Loch Rannoch. 

 This region, at the glacial period, seems to have been a sort of 

 cap or ice-shed from which the ice moved in various directions. 

 Geological maps indicating glacial drift show that ice moved, 

 in the time of confluent glaciers, after the climax of the Ice 

 Age, down the line of the Tummel, down the Lyon, into the 

 Loch Tay region, and also down upon Loch Tulla and Glen 

 Orchy, all radiating from the Moor of Rannoch. Not only do 

 ice markings show this, but boulders of diorite and hornblendic 

 granite from the same source, are peppered about in the regions 

 named, and even carried apparently as far as Glen Almond 

 across the water-shed. 



The Tummel, from its source above Loch Ba to its junction 

 with the Tay at Ballinluig, measures 58 miles, the outlet of 

 Loch Rannoch, which may be regarded as the real commence- 

 ment of the river section, being as far from the source of the 

 Ba as it is from the junction with the Tay. 



