Near Oban, there is a beautiful instance of how much the form of the slate strata depends on the adjacent lime stone strata. Two parallel limestone strata, each about eighteen inches in thickness, ascend with a gentle cur vature, hardly to be distinguished from a straight line. Between these, are two strata of slate, separated by a thin stratum of limestone ; which latter stratum, instead of being parallel to the first-mentioned limestone strata, ascends between them in a serpentine form, giving the adjacent slate strata a figure deeply serrated. The frac ture sustained in consequence of curvature is in this case very strikingly exemplified. In slate rocks, the fissure or direction in which they may be split by a wedge, and the cross cut which determines the dimen sions of the flags into which they break, merit particular attention. These are readily mistaken for the stratifica tion, but are exceedingly distinct from it. In all the slate strata, which we have had an opportunity of ex amining, the plane of the fissure in any stratum con tinues parallel to itself, whatever may be the contorsions to which the stratum has been subjected ; and the line in which the plane meets the surface of the stratum is uniformly parallel to the ridges of the waves into which the stratum is bent ; while in different strata the inclination of the plane of fissure is various. Thus, in a small slate rock near Dunolly, there are two arched strata, one of which is incumbent on the other. The fis sure of the lower is horizontal, and of the upper one ver tical. The cross cut in slate rocks is generally at right angles to the fissure ; and whatever may be the other strata in the rock, it seems to determine the rents by which the rock is cut.
The rocks most apt to obtrude themselves on the eye of the traveller, are pudding-stone and sand-stone, in cumbent on the strata which we have been describing. The pudding-stone is composed of rounded stones, of quartz, granite, jasper, Sec., embedded in the sand-stone, which consists of minute angular fragments, cemented generally by lime. The strata of these rocks are nearly horizontal, much fractured and disturbed by numerous slips. The fracture has an even surface, and in its course cuts through the rounded pebbles of which the rock is composed. No such contorsions as occur in the slate strata are to be observed in these rocks. From the crumbling nature of the pudding and sand-stone it is difficult to observe their junction with the subjacent rock ; but wherever this can be observed, the waves of the slate and limestone are found to have their summits broken off, and the pudding-stone, at the place of junc tion, contains their angular fragments. Numerous bars of whin, cut indiscriminately through the various rocks which occur in this district. They run in a N. N. W.
direction, which, from its coincidence with the direction of the cross cut in the slate, is probably dependent on it. The following seems to be the literal translation of these phenomena. This country is of two formations at distinct and remote periods. In the first of these, the slate and limestone strata were deposited on a great er surface than they now occupy. They were subse quently acted on by some force, which increased their depth, and diminished their extent, by at least a third of their former dimensions. The direction of this force must have been from the south-east or north-west. The limestone was then in a state of softness, approaching to that of chalk, mixed with clay, and the slate still more flexible, so as to yield to the difference of speci fic gravity between it and the limestone. After this compression the slate acquired the species of crystalli zation, on which fissure depends, and the different strata hardened to rock. In this state they remained exposed for a long period, perhaps several centuries, till the slate and limestone rock began to fall to pieces, and sustained a considerable decay. A second formation then took place. Water-worn stones, fine sand, and mud, were by some cause deposited on the original strata, and consolidated into rock. After this consoli dation, rents were somehow produced, occasioning those vast chasms which we now see filled with whinstone. What was the ;:era of the different formations, what the astonishing power which could compress the first for mation, throughout an extent of nearly forty miles, what rendered the strata then fluid, and subsequently pro duced their induration ? How or whence was the second formation conveyed to its present situation ? What sub sequent convulsion produced the extensive rents through both formations, and filled them with whin ? These, and several other queries, suggest themselves to the inqui sitive mind, but their consideration would lead us into the disputed ground of hypothesis. So far as we have gone, we are led by the facts, not by preconceived opi nions. Little acquainted with geology, and partial to DO system, we at first regarded the strata with an apa thetic indifference ; but we shortly, with a species of awe, perceived ourselves in a theatre, where astonishing powers had exerted themselves, and the remote convul sions of nature seemed unfolding themselves to view ;— the scene became interesting, and led us to the conclu sions we have deduced above. They have probably been deduced by many others. To us they spring from the phenomena. Population in 1755, 63,291. Population in 1790-1798, 76,000 ; and in 1801, 75,701. See Johnson's, Pennant's, and Garnet's Tours, and Faujas de St Fond's Travels. See also BERGONIUM, CORRY VRECAN, DUN STAFFNAGE, ICOLMKILL, ISLAY, and STRONTIAN. (4')