J. W. JUDD ON THE SECONDARY ROCKS OF SCOTLAND. 



695 



impossible to draw any sharp line of demarcation between them, 

 though their difference of age is so enormous, and in other localities 

 they are separated by thousands of feet of strata. To the west the 

 Poikilitic strata of Gribun, with the overlying Cretaceous, rise gra- 

 dually in the cliff till they are overwhelmed and concealed by the 

 vast taluses descending from the overhanging basaltic precipices of 

 the grand peninsula of the Bourg. It is probable, too, that they are 

 cut off to the west by a great fault, which carries them below the 

 sea-level. 



Fig. 8. — Sketch taken near Becjs Gave, on the Southern Shore of Loch 

 na Real, opposite Inch Kenneth. 



a. Conglomerates and sandstones of Poikilitic age, covered by Cretaceous (Upper 



Greensand) strata. 



b. Purple quartz, quartz-schist and gneiss. 



In concluding this account of the Poikilitic strata of the Western 

 Highlands, it is impossible to abstain from again expressing the strong- 

 est protest — a protest based on convictions that have gained strength 

 with successive years of work in the district — against the acceptance 

 of negative evidence in this case, and against the view that similar 

 strata to those exposed at so many points between Gruinard Bay and 

 the Gribun might not originally have extended far beyond those 

 limits. When we look southward to Antrim and northward to 

 Sutherland and Elgin, where beds of similar age and character 

 reappear, we cannot but feel that it is impossible to limit the former 

 extent of this formation to the particular regions wherein traces of 

 it have been accidentally preserved, or to avoid the conclusion that 

 wide areas now exhibiting no traces of deposits of this age were once 

 buried under hundreds, or even thousands, of feet of the Poikilitic 

 beds. 



C. The Jurassic System. 



As already pointed out in the introduction to this paper, the fact 

 of the existence in the Western Islands of Jurassic deposits of con- 

 siderable thickness and importance has long been known to geolo- 



