524 REV. R. B. WATSON ON THE GREAT DRIFT-BEDS WITH SHELLS 



From the sandstone region, the rise is generally a steep one, and marked in 

 the burns by a waterfall. This is the edge of the felstone district, where the 

 sandstones, though present, and often considerable in depth, occupy but a small 

 superficies. Here the land rises in faster slopes, to a height of 1200 or 1500 feet. 

 The felstone varies A^ery much. In the south-east it is generally a grey yellow or 

 pink felstone, very friable, disintegrating to soft sand with great rapidit}^ some- 

 times columnar, sometimes also amygdaloidal, and frequently markedly lami- 

 nated, a quality plainly due to the unequal cooling of the mass while in motion. 



In the south-west again, this felstone is sparingly present, and the prevalent 

 igneous rock is a very beautiful felstone porphyry, with a matrix of close-grained 

 compact felstone, sometimes approaching in texture to hornstone, pinkish and 

 yellowish, but most often grey in colour, and containing large crystals of Avhite 

 orthoclase and irregular rounded granules and lumps of crj^stalline quartz. 

 Above the feist ones rise tabular masses of greenstone, which occasionally reach 

 a height of 2000 feet. They are of no great extent, but have been largely 

 eroded. 



The combined result of these features is a table-land with long slopes and 

 rounded contours, rising in hummocky elevations in the distance, and nmch in- 

 tersected by valleys. 



Over the whole of this table-land lie clays and sands. 



Superficial sand-beds are not common, but occur here and there, from 50 to 

 570 feet above the sea. Stratified gravels and clays are to be found in the basins 

 which occur in nearly all the valleys. 



Markedly distinct from these two classes of superficial beds, is the great 

 deposit of coarse red boulder-clay, which swathes hill and valley in a dense mantle, 

 and gives its characteristic feature of rounded outline to the scenery. (PI. XXL 

 fig. I.) 



It may be found on the very edge of the beach. It lies deep over the terrace 

 which rises steeply from the shore along the coast line, and is only absent where 

 this terrace towers up in a great precipice of igneous rock, as at Leac-a-breac, 

 Benan-head and Dippin. 



From 50 to 300 feet above the sea, it reaches its greatest development, pre- 

 senting banks in the water-courses from 80 to 140 feet high. On the hill slopes, 

 as might be expected, it is shallower, and in the valleys too, as they rise into the 

 uplands, the banks of boulder-clay become smaller. Even there, however, they 

 are still considerable, and at a height of 520 feet, I found one face of the boulder- 

 clay 110 feet high.* 



The greatest measured height at which I ascertained the presence of the 



* I need hardly say, that the sections formed by the burns are transverse to the bedding of the 

 lioulder-clay ; and, therefore, that the above measurements do not give the true deptli of the deposit, 

 but only the height of the sections. 



