94 GENERAL REMARKS ON THE 



cealed by the sea. The detached portions which occupy 

 the shore, confirm this opinion; and in extending this 

 view to the islands of similar formation, we are tempted 

 to imagine that the large intervals now occupied by 

 the sea, were once parts of a continuous tract of land. 



The remarks already made on Sky, show that this 

 red sandstone graduates into gneiss ; and similar grada- 

 tions will be found to occur on the mainland. They are 

 visible in Loch Alsh, in Glen Elg, and in Loch Carron ; 

 and, in all these places, the transition is effected, as in Sky, 

 by means of the varieties of schist and grey indurated 

 sandstone there enumerated and described. In Suther- 

 land, that gradation takes place by means of quartz rock ; 

 which on the one side exhibits a transition into the red 

 sandstone, and on the other into gneiss. 



In a large proportion however of the mainland, no such 

 transitions are found, but there is a sudden and complete 

 alternation of the two rocks. This is more particularly 

 the case from Loch Kishorn northwards ; nearly the whole 

 tract consisting of the red sandstone only, free from all 

 the alternating schists and grey sandstones that occur 

 in the places just mentioned. It might perhaps be 

 hence imagined that these were different formations ; but 

 that suspicion is removed by the facts visible in Sky and on 

 the adjoining continent, where the same red sandstone that 

 can be traced to Loch Kishorn and to Loch Alsh, alter- 

 nates with the schistose rocks in question ; as well as by 

 the connexion of the Croulin islands already pointed out. 

 The alternations with gneiss are visible at Loch Carron 

 and great Loch Broom ; the sandstone in the latter place 

 lying beneath the gneiss, end both having a common dip to 

 the south-east.* It was also already remarked in treating 

 of Sky, that the sandstone occurred on the shore of Glen 

 Elg, interposed with a common dip between the gneiss of 

 this island and that of the mainland ; and in the same 

 manner it is found alternating with this rock in Loch 



* Plate XXXI. fig. 2. 



