XCH PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May I9O4, 



less prolonged interval of rest than the 50-foot beach. It is not only 

 post-Glacial, but in some places contains traces of Neolithic man. 



In the structure of these old sea-margins a feature of special 

 interest is presented by the platforms which have been eroded out of 

 the solid rock, and which afford not a little light as to the origin 

 of the Norwegian seter. On the east side of Scotland these plat- 

 forms have been to a great extent cut in Boulder-Clay — a material 

 that would offer comparatively feeble resistance to erosion. On the 

 western coast, however, the rock-platforms, both of the 50-foot and 

 the 25-foot beaches, have been in large measure cut out of much 

 more enduring materials. The rock- shelves of the east side of Jura 

 have been levelled in hard schists and quartzites ; those so con- 

 spicuous around the island of Lismore in the Linnhe Loch, out of 

 massive pre-Cambrian limestone. In Mull and the other members 

 of the Inner Hebrides, they have been eroded in various rocks of 

 the Tertiary volcanic series. In the Firth of Clyde, they have 

 been planed down among the sandstones and igneous rocks of the 

 Carboniferous and Triassic formations, as well as here and there in 

 Boulder-Clav. 



The surface of these rock-terraces is flat, and usually covered with 

 a thin coating of grass-grown soil through which harder knobs and 

 stacks of the underlying rock here and there protrude. At the 

 inner margin of the terrace, the rocks rise into a cliff or steep bank, 

 the base of which is frequently pierced with caves. That these 

 caves were mainly due to erosion by moving water is abundantly 

 evident in the rounded and smoothed surfaces of their sides. Their 

 floors are often rough with round shingle, which has undoubtedly 

 been the material employed by Xature in their excavation. jSTo one 

 who has made himself familiar with the rock -platforms which at 

 the present day are in course of erosion by the sea along these same 

 coasts, can for a moment doubt that the rock-platforms of the raised 

 beaches which, down to the minutest point, resemble them, have 

 likewise been eroded by the waves of the sea. Xowhere have I 

 seen this lesson more instructively taught than at Kincraig Hill on 

 the coast of Fife, an old volcanic vent which, from a height of 

 200 feet above the sea, descends in vertical precipices to the edge 

 of the present beach. Hound the west side of the hill the three 

 terraces (100-foot, 50-foot, and 25-foot) have been cut out of the 

 volcanic agglomerate as parallel shelves or seter. At the foot of 

 the cliffs when the^tide is out, one can walk for half a mile upon 

 a broad flat platform, which is now in course of erosion out of the 



