Extract

Scotland may be roughly divided into three geological bands—1st, A northern area including the Highlands and Islands; 2nd, The broad belt of the Lowlands, embracing the lower portions of the basins of the Tay, Forth, and Clyde; and 3rd, The high pastoral uplands and rich agricultural valleys that lie between the Central Lowlands and the English Border. Of these bands the first and the third are composed in great measure of rocks of Lower Silurian age, while the second is occupied chiefly by the Old Red Sandstone and Carboniferous series, the Silurian rocks may thus be regarded as forming the general framework of the country. They spread over the southern uplands, and then sinking under the central valley of the lowlands, rise up on the farther side in a metamorphosed form, stretching far and wide as the gneisses, schists, limestones, and quartz-rocks of the Highlands. It is of course in the unmetamorphosed or southern belt that the order of succession among the Scottish Silurian rocks must first be studied.

I.—LOWER SILURIAN REGION OF THE SOUTH OF SCOTLAND.

Owing to the contorted and broken state of the rocks composing the Lower Silurian belt of the South of Scotland, it is by no means an easy task to reduce them to a satisfactory order of succession. They have been thrown into endless plications and contortions; it is chiefly the edges of their vertical or highly inclined strata which are seen cropping up in the channels of streams or on bare hillsides, and

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