22 [Proc. B.N.F.C, 



face of the sheet became subject to atmospheric influences, 

 wind, and rain, which decomposed the surface, forming a 

 thin coating of soil. As the basic rocks contain a large pro- 

 portion of iron, so we find the resulting soils containing also 

 much iron. Sometimes the alumina compounds were washed 

 into the valleys, and from such soils have resulted the sub- 

 stance known as bauxite, from which aluminium is extracted, 

 as in the works at Larne Harbour. But after a short inter- 

 val another outburst would occur — another lava flow take 

 place, covering up and scorching the thin coating of soil, and 

 leaving a reddish band as the only remnant of the soil and 

 vegetation that had flourished, and marking the limits of one 

 flow from another. Such a course of events can be traced 

 in the fine headlands of the Gobbins, where one flow is dis- 

 tinctly marked from another by these red bands, and also by 

 the difference in character of the respective flows. Some of 

 the beds are massive and black, others are black, but contain 

 cavities filled with white crystalline matter known as zeolites. 

 These can be admirably studied in the Gobbin rocks, and open 

 up a wide field for investigation. Have these zeolites crys- 

 tallised from highly-heated vapours, or have they resulted 

 from chemical changes that have taken place in the rock after 

 its deposition, or have both methods been employed by 

 Nature ? Volcanic action has now ceased as far as our country 

 is concerned, but the same disturbances only shifted further 

 north, changing in character, and are still to be found in 

 operation in Iceland. But what is left to us in Antrim and 

 the various islands of the West of Scotland is only the 

 remains of a vast plateau of basalt that covered the entire 

 district. The channel that separates the Antrim sheets from 

 the Scottish must, therefore, represent a vast period of time 

 during which denudation has been going on steadily but 

 surely; during this period of time the sea and air have 

 weathered away the intermediate rocks, and leave us now the 

 bold cliffs which form the striking scenery of our Antrim 

 coast. Face to face with these precipices of the Gobbins we 

 have some of the most momentous lessons of geology deeply 



