1 908-1909.] on the Scenery of Scotland. ill 



places reached a depth of 3000 feet. The lava plateau 

 originally skirted the western Highlands, stretched westwards 

 far beyond the Inner Hebrides, to the south embraced north 

 Ireland, on the north perhaps reached even to the Faroe 

 Islands and Iceland. But so severely has this supposed plain 

 suffered from the destroying action of atmosphere and sea, 

 that now it is represented in the Scottish area by only a few 

 isolated patches — the isles of the Inner Hebrides — which 

 show unmistakable evidences of their origin in the horizontal 

 rock-bands that pattern their cliffs, clearly indicating the 

 succession of the lava streams. Some of the grander effects 

 of the Tertiary eruptions are well shown in the islands of 

 Skye, Eum, Eigg, Mull, Arran ; some of the more minute are 

 to be seen in Fingal's cave and the Clamshell cave in Staffa, 

 where the weather, acting along the regular joints which 

 frequently form in cooling lava, has sculptured piles of regular 

 columns. 



Since the Tertiary eruptions Scotland has again lapsed into 

 a period of quiescence which still continues. But during all 

 this time the ceaseless destroying action of the weather has 

 been going on, modifying the shapes of the extinct volcanoes 

 and their products, softening their outlines, and yet at the 

 same time carving out for us some of our most characteristic 

 volcanic scenery by emphasising the regular meshwork of 

 cracks and joints which traverse most of the denser volcanic 

 materials. Owing to their hardness and to their power of 

 resisting the ravages of air and sea more successfully than the 

 neighbouring rocks, volcanic products in general stand out 

 above the common level of the surrounding country, express- 

 ing themselves as hills and prominent knobs. On this account 

 their influence on our scenery is most marked, for were we to 

 subtract all volcanic products, for example from the midlands 

 of Scotland, there would remain in that area nothing more 

 interesting than a comparatively flat, hummocky sweep of 

 country ; Strath More would be magnified into a still greater 

 strath, stretching from the Grampians in the north almost to 

 the southern Cheviots. 



[The characteristic types of Scottish volcanic scenery de- 

 scribed in the lecture were illustrated by lantern views.] 



