1910-1911.] 



359 



hill, there are also very interesting examples of sills and dykes. 

 The sills traversing the sandstone are exposed in the face of the 

 quarry in the same striking manner as those in the one just 

 visited, but the uppermost sills could be traced, branching from a 

 vertical dyke, and following a horizontal course along the bedding 

 planes of the sandstone, though occasionally for a short distance 

 breaking through them. At the opposite side of the quarry 

 another very interesting vertical dyke was traced at intervals, for a 

 long distance traversing the sandstone. These remarkable 

 sections of intrusive sheets and dykes laid open in the quarries of 

 Scrabo Hill are perhaps the finest of their kind in the British 

 Isles. It is to the protection of the dolerite that the sandstone 

 of Scrabo Hill owes its preservation, the soft sandstone in the 

 vicinity having been greatly denuded. This sandstone has 

 been correlated with the Lower Keuper sandstone of Lancashire 

 and Cheshire, but the question has also been raised as to whether 

 the correlation should not be with the nearer Trias of the Isle of 

 Man, and the point does not yet seem to be definitely determined. 



TARDREE, SANDY BRAES, AND CARNEARNEY. 



The Geological Section held its second excursion of the 

 season on the 7th May, with the object of investigating the 

 rhyolites of Tardree, Sandy Braes, and Carneamey. As the occur- 

 rence of these acid rocks forms an interesting episode in the 

 geological history of County Antrim, it may be well to recall a few 

 of the earlier changes of surface. When the Cretaceous ocean 

 passed away, the sea floor was upraised, and formed Chalk downs, 

 similar to those of the South of England. In early Tertiary times 

 numerous fissures appeared, running from north-east to south-west. 

 Molten basaltic lava welled up through them, and flowed over the 

 Chalk downs in successive sheets, forming the Lower Basalt series. 

 A period of quiescence followed ; then lavas of a different type 

 were intruded, and where they appeared at the surface in County 



