The Great Conglomerate--Its Undulatory and Rectilinear Members--Knock Farril and its Vitrified Fort--The old Highlanders an observant race--The Vein of Silver--Summit of Knock Farril--Mode of accounting for the Luxuriance of Herbage in the ancient Scottish Fortalices--The green Graves of Culloden--Theories respecting the Vitrification of the Hill-forts--Combined Theories of Williams and Mackenzie probably give the correct account--The Author's Explanation--Transformations of Fused Rocks--Strathpeffer--The Spa--Permanent Odoriferous Qualities of an ancient Sea-bottom converted into Rock--Mineral Springs of the Spa--Infusion of the powdered rock a substitute--Belemnite Water--The lively young Lady's Comments--A befogged Country seen from a hill-top--Ben-Wevis--Journey to Evanton--A Geologist's Night-mare--The Route Home--Ruins of Craighouse--Incompatibility of Tea and Ghosts--End of the Tour. I was once more on the Great Conglomerate,--here, as elsewhere, a picturesque, boldly-featured deposit, traversed by narrow, mural-sided valleys, and tempested by bluff abrupt eminences. Its hills are greatly less confluent than those of most of the other sedimentary formations of Scotland; and their insulated summits, recommended by their steep sides and limited areas to the old savage Vaubans of the Highlands, furnished, ere the historic eras began, sites for not a few of the ancient hill-forts of the country. The vitrified fort of Craig Phadrig, of the Ord Hill of Kessock, and of Knock Farril,--two of the number, the first and last, being the most celebrated erections of their kind in the north of Scotland,--were all formed on hills of the Great Conglomerate. The Conglomerate exists here as a sort of miniature Highlands, set down at the northern side of a large angular bay of Palaeozoic rock, which indents the _true_ Highlands of the country, and which exhibits in its central area a prolongation of the long moory ridge of the Black Isle, formed, as I have already had occasion to remark, of an _upper_ deposit of the same lower division of the Old Red,--a deposit as noticeable for affecting a confluent, rectilinear character in its elevations, as the Conglomerate is remarkable for exhibiting a detached and undulatory one. Exactly the same features are presented by the same deposits in the neighborhood of Inverness; the _undulatory_ Conglomerate composing, to the north and west of the town, the picturesque wavy ridge comprising the twin-eminences of Munlochy Bay, the Ord Hill of Kessock, Craig Phadrig, and the fir-covered hill beyond in the line of the Great Valley; while on the south and east the _rectilinear_ ichthyolitic member of the system, with the arenaceous beds that lie over it, form the continuous straight-lined ridge which runs on from beyond the moor of the Leys to beyond the moor of Culloden. There is a pretty little