The scenery of Scotland Author:Archibald Geikie Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: WEATHERING OF ROCKS of the discoverer of carbonic acid, I could not but reflect on the curious irony of Nature, that has furnished in the corrosion of his mon... more »ument her own testimony to the truth of his discovery. As the result of my inquiries, I found that in such a climate as that of Scotland, marble tombs freely exposed to the weather are destroyed in less than a century. The rate of superficial disintegration amounts sometimes to about a third of an inch in that time. The limestones and marbles which occur so abundantly in the Fig. 1.—Granite weathering along its joints near the top of Ben na Chie. Aberdeenshire. Highlands and Lowlands must thus be liable to great and rapid decay.1 Sandstones being largely made use of for building and monumental purposes, many opportunities are afforded of examining their mode of weathering. The more com pact and siliceous kinds are remarkably durable, retaining 1 See an essay on Rock Weathering measured by the decay of tombstones, in my Geological Sketches at Home and Abroad, p. 182. their chisel-marks even after the lapse of two centuries. Where a soluble or easily removable matrix, however, holds the component grains together, sandstone may be rapidly disintegrated; while, if divided by well-defined laminae, the stone is pretty sure to split up or peel off along these planes of separation, as air, rain, and frost alternately attack it. The crystalline rocks present many interesting varieties of weathering. The joints by which they are so abundantly traversed serve as channels for the action of percolating water and frost, and hence as lines along which the rocks are split open. In such a rock as granite, for instance, where one set of joints runs in approximately parallel planes, the influence of weathering causes the r...« less