594 J. G, Goodchild — Deutozoic Eocks of North Britain. 



to be presently referred to. One of the most impressive geological 

 phenomena I ever witnessed was presented by a section in the 

 Basin of the Lune, of the Upper Old Red Sandstone lying in 

 a nearlj' horizontal position upon vertical and highly-cleaved Upper 

 Ludlow Rocks, of fragments of which the newer rock was largely 

 composed. This was in the course of my first week's field-work 

 on the Geological Survey, in 1867. Ever since then my recollection 

 of that enormous hiatus has remained as vivid as at first, and it has 

 added not a little to the pleasure afforded by somewhat extensive 

 explorations made in recent years amongst the Scottish rocks which 

 partly bridge over the vast gap. An unconformable junction of 

 Cornstones on Highland Schists, exposed on the north shore of 

 Arran, is hardly less striking ; as is the better known case at the 

 Siccar Point, where the Upper Old Red lies upon Gala Rocks. 



UncouforniaMe Junction of Cornstones with Highland Scliists. north sliore of Arran^ 

 east of Loch Eanza. 



It adds still further to the impressive character of the uncon- 

 formity at the base of the Upper Old Red Sandstone of the Lake 

 District that this rock also contains rolled fragments of the granites, 

 elvans, and porphyrites of that part. These plutonic and trappeau 

 rocks are certainly of later date than the cleavage of the rocks they 

 invade and also than one phase of the great denudation that followed 

 the development of the cleavage. That is to say, after the Protozoic 

 rocks of the Lake District were folded, they were first cleaved, then 

 denuded to an enormous extent ; after that, great volcanoes rose 

 upon the denuded surface, and, finally, the volcanoes themselves 



