J. W. JUDD ON THE SECONDARY ROCKS OE SCOTLAND. 691 



series of Jurassic strata which is so finely exposed in the magnificent 

 precipices of Hallaig and Screpidale. The strata which are here 

 seen in passing downwards from the Infralias rocks that lie imme- 

 diately and conformably above them are as follows : — 



(1) White, reddish, mottled, and ferruginous sandstones, exhibiting much false 



bedding, and becoming conglomeratic in places. These beds contain 

 many limestone fragments, and in places much calcareous matter in their 

 matrix. Their thickness is at least 80 feet. 



(2) Red and mottled clays and marls, often very sandy, and sometimes conglome- 



ratic. These beds pass in places into true sandstones and conglomerates, 

 and contain some bands of concretionary limestone. Thickness 60 feet. 



(3) Conglomerates (formed of rounded or subangular fragments of white and 



purple quartzite, of Torridon Sandstone, and of compact or subcrystalline 

 limestone) alternating with irregular lenticular beds of coarse micaceous 

 sandstone, into which the conglomerates often insensibly graduate. These 

 beds exhibit reddish and greenish tints, and closely resemble in character 

 the lowest beds of Gruinard Bay. Thickness seen 60 feet. 



This series of strata is thrown against beds of Middle-Lias age by 

 the great Hallaig fault, which has a throw of at least 700 feet (see 

 fig. 2, p. 671). It is probable that these 200 feet of strata at Eu- 

 na-Leac comprise nearly the whole section of the Poikilitic in this 

 island ; but as the Torridon Sandstones have not been seen to make 

 their appearance from beneath the conglomerates even at the lowest 

 tides, it is impossible to speak with certainty upon the question. 



At a point called Ayre, in the same island of Eaasay, and lying 

 south of Eu-na-Leac, there is found a conglomerate resting uncon- 

 formably upon the Torridon Sandstone, and largely made up of its 

 fragments, but with the addition of some pebbles of limestone ; and 

 this, there can scarcely be the smallest doubt, belongs to the base of 

 the series, all the upper beds having been removed by denudation. 



At Castel Brochel, in Eaasay, several miles to the north of Eu-na- 

 Leac, another mass of conglomerate makes its appearance upon a 

 projecting headland, on which the famous and singularly situated old 

 Highland stronghold is perched. As the conglomerate in question, 

 however, is very different in many of its characters from the Poiki- 

 litic beds of the area, especially being distinguished from them by 

 containing no limestone fragments as well as in its general aspect, and 

 as, moreover, the relations of the isolated patch of conglomerate are of 

 a doubtful and indeterminate character, I find no grounds on which to 

 assign it either to the Poikilitic or to any other part of the Secondary 

 series of strata. 



The Poikilitic beds in Eaasay appear to have a much less thickness 

 than those of Gruinard Bay ; and when we proceed southward into 

 Skye that thickness is found still further diminished, and the forma- 

 tion in question is thus reduced to a merely rudimentary condition. 

 Beds of pebbles, constituting a thin conglomerate band, have been 

 detected at several points at the junction of the Jurassic strata and 

 the Torridon Sandstone at Strath in Skye. In the coast-section at 

 Lussay there is evidently an interval between the Jurassic rocks and 

 the Torridon Sandstones that unconformably underlie them ; but the 

 strata in this interval are only very imperfectly exposed even at the 



