John MacCulloch

“ A few fallen stones have formed a sort of cave capable of containing three or four persons, and known to the neighbouring shepherds, who, still mindful of their ancient allegiance, show the spot where, among many others, the unfortunate Prince was for a time concealed. The minuter fragments of quartz rock and granite have here formed themselves into angular conglomerates, which are in some instances perfectly compact, the smaller cavities having been filled up by siliceous matter, while the larger fragments, touching only by small surfaces, have left considerable openings between them. ”

“ Nevertheless I am still inclined to think that even those which are occasionally seen conforming to the position of the strata in which they lie, are, like the masses of trap which have a direction parallel to the associated beds, only veins, of which the direction is so far parallel to the position of the beds in which they are found. ”

“ The collective breadth of the strata where they are widest, appears to be about a mile and a half, while at each end it is much less, but the nature of the ground does not permit their whole extent or geographic shape to be accurately ascertained. In a general view they form two irregular ranges of parallel elevations, with shallow intermediate vallies, and as these summits maintain scarcely any vegetation, while they are composed of white compact quartz, their effect is very striking, even at a great distance ”

“ The most crystallized and pure specimens of quartz rock afford this variety, and examples of it are to be found every where among the more compact beds of that rock. We may therefore conclude that the avanturine, so much esteemed and long so ill understood, is a variety of quartz rock ”

“ While the nature of these strata, which present alternations of red sandstone with graywacké schist, and with indurated grey and blue granular quartz, would incline us to rank them among the secondary rocks, some doubt is thrown on that conclusion in consequence of the peculiar relation they bear to the older rocks which they follow, the gneiss, and the micaceous and chlorite schists. ”

“ These beds are divided by natural joints, at angles with the plane of stratification, and in consequence of this they break into prismatic rhomboidal or triangular fragments, which on the upper and long-exposed surfaces are so numerous and minute that the whole presents at first sight a set of sharp points and projections, among which the stratified disposition is scarcely perceived until they are more closely examined. ”

“ It is found in most parts of the valley of the Tumel, which extends from the head of Loch Rannoch to the junction of the Tumel with the Garry. Throughout this whole extent it alternates with schist, sometimes micaceous, now and then containing felspar and thus resembling gneiss in composition, but oftener argillaceous, and very hard, from the large proportion of quartz which it contains. As we approach the lower end of this valley the quartz rock diminishes, while the schist increases, until the former at length disappears. ”