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The eastern and western seaboards present a singular contrast. The eastern is indented by a series of broad arms of the sea - the Firths of Forth, Tay, Moray, and Dornoch - but is otherwise unbroken. The land slopes gently to the sea or to the edge of cliffs that nave been cut back by the waves. The shores are for the most part low, with few islands in front of them, and cultivation comes down almost to the tide line. The western side on the contrary, is from end to end intersected with long narrow sea lochs or fjords. The land shelves down
rapidly into the sea and is fronted by chains and groups of islands. The explanation of this contrast must be sought in geological structure. The west side, as we have seen, has been more deeply eroded than the eastern. The glens are more numerous there and on the whole deeper and narrower. Many of them are prolonged under the sea; in other words, the narrow deep fjords are seaward continuations of the glens. The presence of the sea in these fjords is an accident. If they could be raised out of the sea they would become glens, with lakes filling their deeper portions. They are submerged land valleys, and as they run down the whole western coast they show that this side has subsided to a considerable depth beneath its former level. The Scottish sea lochs must be considered in connection with those of western Ireland and Norway. The whole of this north-western coastline of Europe bears witness to recent submergence. The bed of the North Sea, which at no distant date in geological history was a land surface across which plants and animals migrated directly into Great Britain, sank beneath the sea-level, while the Atlantic advanced upon the western margin of the continent and filled the seaward ends of what had previously been valleys open to the sun. In this view the Outer and Inner Hebrides were formerly one with themselves and the mainland, and the western isles therefore are truly grouped with the Highland province of Scotland. Nearly the whole coastline is rocky. On the east indeed the shores of the estuaries are generally low, but the land between the mouths of these inlets is more or less precipitous. On the west the coast is mostly either a steep rocky declivity or a sea-wall, though strips of lower ground are found in the bays. The cliffs vary in character according to the nature of the rock. At Cape Wrath, precipices 300 ft high have been cut out of the Archean gneiss. The varying texture of this rock, its irregular foliation and jointing, and its ramifying veins of pegmatite give it very unequal powers of resistance. Here it projects in irregular bastions and buttresses, there retires into deep recesses and tunnels, but shows everywhere a ruggedness of aspect eminently characteristic. In striking contrast to these precipices are those of the Cambrian red sandstone a few miles to the east. Vast vertical walls of rock shoot up to a height of 600 ft cut by their perpendicular joints into quadrangular piers and projections, some of which stand out alone as cathedral like islets in front of the main cliff. The sombre colouring is relieved by vegetation along the edges of the nearly flat beds which project like great cornices and serve as nesting places for sea-fowl. On the west the most notable cliffs south of those of Cape Wrath and the Cambrian sandstone's of Sutherland are to be found among the basaltic islands, particularly in Skye, where a magnificent range of precipices rising to 1000 ft bounds the western coastline. However, the highest cliffs are found among the Shetland and Orkney Islands. The sea-wall of Foula, in Shetland, and the western front of Hoy, in Orkney, rise like walls to heights of 1000 or 1200 ft.. 
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