724 J. W. JUDD ON THE SECONDAEY EOCKS OF SCOTLAND. 



In the northern part of the area we are describing, as in Skye 

 and Eaasay, only the divisions I. and II. occur, III. being wholly 

 wanting, or, as is not improbable, represented by the more purely 

 marine beds I. of the Inferior Oolite. The uppermost division of 

 the Loch-Staffin beds, first described by Macculloch, was referred by 

 Murehison, on account of the peculiar characters of its beds and the 

 general facies of its fossils, to the Wealden ; and its true position in 

 the geological series, as underlying strata containing Oxfordian 

 fossils, was first shown by Edward Forbes in 1851 *. 



These same strata can also be traced lying at the top of the whole 

 series of Secondary strata both in Skye and Eaasay. In the former 

 island they are seen not only in the mural cliffs on the east side of 

 the Trotternish peninsula, but extend some distance inland, and are 

 exposed by the denudation of the overlying basaltic lavas around 

 Lochs Leithan and Eada, as pointed out by the late Dr. Bryce. 

 They again make their appearance, but at much lower levels, at 

 other points around the Trotternish peninsula, as at Aird and 

 Duntulm ; but in all these cases the strata have undergone great 

 changes owing to the intrusion into their midst, during Tertiary 

 times, of great masses of igneous rock. Thus the sandy beds are 

 found converted into chert and quartzite, the clays into a hard and 

 brittle material, breaking with a conchoidal fracture, and resembling 

 Lydian stone, and the limestones into saccharoid marble. Further 

 west in Skye, in the peninsulas of Yaternish and Qnirinish, strata 

 belonging to this part of the series are exposed on the coast, where 

 they are seen lying under the thick series of Miocene lavas at Stein 

 in Loch Bay, and at Copnahow Head. These exposures are in- 

 teresting, as showing how widely spread is the great foundation of 

 Secondary rocks lying beneath the Miocene basalts which cover all 

 the northern part of the island of Skye. 



In the island of Eaasay the Great Estuarine Series is presented to 

 us with a series of relations remarkably parallel with those which 

 prevail in Skye. On the eastern coast the strata in question are 

 seen at a great elevation, occupying, indeed, the highest crest of the 

 island immediately below the isolated cap of basaltic lavas of Dun 

 Can, by which they have been saved from the destructive action of 

 the denuding forces. The same strata, however, are found rapidly 

 dipping westward, and pass under the sea-level along the east 

 shores of the Sound of Eaasay, which must hence be traversed by a 

 great fault with a throw of something like 1000 feet. 



Passing from the northern to the southern area, it is in the latter, 

 as we have already seen, that the strata of the Great Estuarine 

 Series acquire their most important development. This is well 

 illustrated by the sections in the islands of Eigg and Muck. In the 

 former we, in the north-western part of the island, have a tolerably 

 continuous section of the whole of the strata, though the base is un- 

 fortunately concealed beneath the sea-level. The same beds appear 

 on the eastern side of that island, but are there rendered obscure by 



* Quart. Journ. Geol. Soc. vol. vii. p. 104. 



