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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Feb. 20, 



ill * 



are succeeded by micaceous schists pass- 

 ing upwards into gneiss. This must, as 

 already mentioned, be regarded only as 

 a local circumstance. After leaving 

 Dunkeld for the N.W., the valley of the 

 Tay becomes so expanded that the ex- 

 hibitions of rocks are by no means fre- 

 quent. On approaching Houlinearn we 

 find indications of a reversed dip pre- 

 vailing among the gneissose strata ; but 

 on reaching Pitlochrie at the bridge over 

 the Tummel, a rT.N.W. dip obtains ; and 

 near this we have limestones very abun- 

 dantly developed, inclining at an angle 

 of 35°. The Pitlochrie limestone has a 

 somewhat gneissose appearance, and is 

 to a considerable extent made up of 

 layers of a grey and a white colour, the 

 latter resulting from the deposition of 

 more crystalline carbonate of lime in the 

 hollows produced by the opening of the 

 laminas consequent on flexures and con- 

 tortions. 



This limestone at Pitlochrie in its na- 

 ture has great affinity to that on the 

 north side of Loch Tay ; and there is, 

 from its line of strike, strong reason to 

 regard it as an extension north-east- 

 ward of the Loch Tay beds. 



At Craigeoch, about a mile N.W. 

 from Pitlochrie, we have gneissose rocks 

 coming on ; and these, dipping at 70° 

 represent the rocks of the same 

 character which have been described 

 as succeeding tbe limestones of Loch 

 Tay in the section from this loch to Glen 

 Lyon. Continuing the section north- 

 westwards, we have, in the neighbour- 

 hood of the Pass of Killiecrankie, re- 

 versed or S.E. inclinations among the 

 gneissose rocks ; and at Essangeal a 

 thick grey limestone, with imperfect 

 bedding, and seeming to dip under the 

 gneissose strata, appears. Between Es- 

 sangeal and Blair no rocks are exhibited 

 on the road ; but at the latter spot we 

 have the limestone again shown with a 

 S.E. dip. This limestone of Blair I re- 

 gard as the same as that seen at Essan- 

 geal, and that its appearance here is the 



