01? SCOTLAND.

321

justed armour of many joints, and by tbe massive IllEenus,with its double buckler. With this upper formation of theLower Silurian division, deposition in the earlier Palaeozoic period seems to have ceased in this district. Farther to thesouth, however, on the shores of the Solway, the shales, in asomewhat altered form, pass into the lower beds of the UpperSilurian, and exhibit some of its characteristic fossils. Andwith these the Old Grauwacke record, as a record of life anddeath, abruptly closes in Scotland , and a chapter of purelyphysical revolution begins,—a chapter perplexed by passagesof doubtful meaning, and by many different readings, butwhich tells, in every page, of widely-extended convulsion andupheaval, and of the operations of deeply-seated forces of apower incalculably great.

During the ages of either the Upper Silurian or the infe-rior Old Red Sandstone, the deposits of the Lower Grauwackedivision in Scotland seem to have been the subject of enor-mous lateral pressure, which raised their strata into manyfolds and ridges over wide districts, and, as there is reasonto believe, elevated them above the sea level. Sir Roderick Murchison reckoned in the neighbourhood of Girvan fromfive to six axial lines in a section of less than eight miles;and on the east coast, in the instances made so famous bySir James Hall , axial lines are, as I have already had occa-sion to state, still more numerous. Nay, the great difficultywhich lies in the way of determining the true place of theolder rocks of our southern Highlands arises from the inabi-lity geologists have hitherto experienced of drawing, amid theperplexities of these convolutions, a base line for the whole ;and from the further circumstance that, for great distancestogether, so completely vertical are the strata, that the ascend-ing cannot be distinguished from the descending direction.On visiting the Pentland range of hills for the first time, many

years ago, there was nothing which so impressed me as that

x