Rocaille

“ The rock on which the boulder formation reposes, if it consists of granite, gneiss, marble, or other hard stone, capable of permanently retaining any superficial markings which may have been imprinted upon it, is usually smoothed or polished, like the erratics above described, and exhibits parallel striæ and furrows having a determinate direction. ”

“ We see in one place the primary rock, with its veins of granite and quartz,—its dizzy precipices of gneiss, and its huge masses of hornblende; we find the secondary rock in another, with its bed of sandstone and shale,—its spars, its clays, and its nodular limestones. ”

“ Before us lay a wide expanse of smooth stone, the top of a great rock that had its base in the woods below. Behind us rose a high wall of rock, and beyond that was the sun, now sinking towards the western horizon. ”

“ But in place of sharp-rimmed escarpments, and tors, and broken shattered ridges, we see everywhere a rounded and smoothly-flowing configuration which prevails up to a height of 1600 feet or thereabout, above which the rocks take on the rugged appearance which is natural to them. By what magic have the strata at the lower levels escaped in such large measure from the action of rain and frost, which have furrowed and shattered the higher mountain-tops? ”

“ Lofty mountains, lifted up in rounded forms of granite, gneiss and other igneous rocks, massive and grand, like mighty boulders welded together, with monster trees in the valley below, and tall and straight ones high above wherever a ledge or a fissure affords their hardy roots chance to take hold, flank the road for the first ninety miles. ”

“ The nature of the rock, whether sandstone, shale, limestone, or greenstone, must be set down at the same place, and, to save room, a system of marks for the different rocks may be conveniently used. When a sufficient area of ground has been thus traversed, the student may find, say a row of arrows on his map all pointing due west, and indicating a set of quarries about a quarter of a mile distant from one another, the rock in each of them dipping to the west. ”

“ PRIMARY ROCKS.
Although the earth has not been actually penetrated to a greater depth than three thousand feet, the nature of its substance can, in many instances, be inferred for the depth of many miles by other means of observation. We see a mountain composed of a particular substance, with strata, or beds of other rock, lying against its sloped sides; we, of course, infer that the substance of the mountain dips away under the strata which we see lying against it. ”

“ A tremendous ascent among rocks and pines to a height of 9,000 feet brought us to a passage seven feet wide through a wall of rock, with an abrupt descent of 2,000 feet, and a yet higher ascent beyond. I never saw anything so strange as looking back. It was a single gigantic ridge which we had passed through, standing up knife-like, built up entirely of great brick-shaped masses of bright-red rock, piled one on another by Titans. ”

“ Rocks.—Every one knows that the crust of the earth is composed of very various substances, some of which are hard and crystalline in texture, like granite; others less indurated and non-crystalline, such as sandstone, chalk, shale, &c.; while yet others are more or less soft and incoherent masses, as gravel, sand, clay, peat, &c. ”

“ As you round a sand dune you come suddenly upon a gigantic round, flat-topped rock, like a titanic pink tree-stump—scarcely a reward for all those miles and miles of dreariness and intense heat, even though its flat-chopped top is a thousand feet clear above the surrounding plain. ”

“ The joints by which all rocks are traversed have been especially serviceable as dominant lines down which the rain has filtered, up which the springs have risen and into which the frost wedges have been driven. On the high bare scarps of a lofty mountain the inner structure of the mass is laid open, and there the system of joints even more than faults is seen to have determined the lines of crest, the vertical walls of cliff and precipice, the forms of buttress and recess, the position of cleft and chasm, the outline of spire and pinnacle. ”

“ The structure of the former belongs properly with the original structures of the volcanic rocks; but the latter—the true mountains—owe their internal structure and altitude or relief almost wholly to the crumpling and mashing together of great zones of the earth’s crust, being, as already pointed out, the culminating points of the plication, cleavage, and faulting of the strata. “A mountain-chain consists of a great plateau or bulge of the earth’s surface, often hundreds of miles wide and thousands of miles long. ”

“ Imagine a chasm that at times is less than a quarter of a mile wide and more than a mile deep, the bed of which is a tossing, roaring, madly impetuous flood; winding its way in a sinuous course along walls that are painted with all the pigments known to nature! What an imposing spectacle; what a scene of awesome grandeur; what a sublime vision of mightiness! But the geologist sees in the crags and precipices, the strata and bed of that brawling stream, the handwriting of nature, the easily decipherable physical history and geology of the land. ”

“ The mountains are clad in a scattering growth of scrubby pines, oak, cedar, and furze, and exhibit a very rugged and broken aspect. The rocky formations embodied in them, contrary to the opinion generally received, are of a primitive character, consisting of granite, gneiss, quartz rocks, &c. It {239} should be remarked, however, that a deep crust of secondary rocks, the same as the stratifications of the plains before mentioned, appears [Pg 150] to recline against the east side of the mountains, extending upward from their base many hundred feet. ”

“ The contrast between the smoothly-flowing contour of the lower elevations and the shattered and riven aspect of the harsh ridges, sharp peaks, and craggy tors above, is particularly striking. The mammillated and dome-shaped masses have a pale, ghastly grey hue, their broad bare surfaces reflecting the light freely, while at higher elevations the abundant irregularities of the rocks throw many shadows, and impart a darker aspect to the mountain-tops. ”

“ My favorite one is a huge projecting rock, protected by large upright ones nearly as immense, and shooting out over tier upon tier of rocks, down a hundred feet below, to where the river runs like life—now in sunshine, now in shadow. ”

“ The scenery too is here of the most magnificent description; rocks overhang rocks in ruinous grandeur, and appear so fearfully equipoised, that, although secure in their immensity, they create in the mind the most awful apprehension of their instability, whilst the mighty roar of the ocean beneath, unites in effect with the scenery above.—All around is sublime.——But the Geology, enough of the picturesque.
The body of the rock is composed of Slate and Granite ”

“ On mountain sides, in ravines, and sea cliffs, the rocky masses of the earth are exhibited free from the obscurity of superficial accumulations: the industry of man, in mines, wells, roads, canals, has added to the facilities granted by nature, and from these opportunities the structure of the crust of the earth, the arrangement and relative position of the rocks, are known in the most essential points. ”

“ The old rock stands for the mountains of the Old World, like the Welsh mountains, or the Mendip Hills. The slates stand for the new rocks, which have been piled up against these, one over the other. But, you see, each slate is lower than the one before it, and slopes more; till the last slate which you are putting on is the lowest of all, though it overlies all. ”

“ Where a rain-drop first secures a resting-place, its successors deepen the little hollow. Water lies in this after every shower, working its way gently downwards. In time the rock may seem bored into as if prepared for blasting; the holes unite to form vertical grooves, and the surface is cut deeply into fantastic forms. ”

“ Why, a black and beetling wall of rock rising sheerly perpendicular up out of the water, and towering to a height of over one thousand feet. Although the loch is five hundred yards wide, you can hardly get rid of the impression that this immense wall of rock is bending towards you from the top, and about to fall and crush your pigmy body to atoms. ”

“ The shape of the fragments of stone at the base of our precipice may be called accidental, but this is not strictly correct, for the shape of each depends on a long sequence of events, all obeying natural laws, on the nature of the rock, on the lines of stratification or cleavage, on the form of the mountain which depends on its upheaval and subsequent denudation, and lastly, on the storm and earthquake which threw down the fragments. ”

“ We peer over the verge of the cliffs, still wrapped in their morning shadows, and mark how peak, ridge, and wall of flinty quartzite, glowing in tints of orange, yellow, and red, uprear themselves from the face of the declivity, like the muscles on the limb of some sculptured Hercules, as if the mountain had gathered up its whole strength and knit its frame together to defy the fiercest assaults of the elements. But look how every crag is splintered, how every jutting buttress is rent and creviced, how every ledge is strewn with blocks that have fallen from the naked wall above it! ”

“ To obtain a general idea of the nature and method of our science before beginning its study in detail, we may visit some valley, such as that illustrated in the frontispiece, on whose sides are rocky ledges. Here the rocks lie in horizontal layers. Although only their edges are exposed, we may infer that these layers run into the upland on either side and underlie the entire district; they are part of the foundation of solid rock which everywhere is found beneath the loose materials of the surface. ”

“ They lie in all positions—horizontal, tilted, vertical—with heaps of scoria revealing their igneous origin. Rock is piled on rock, hill upon hill, ridge upon ridge, mountain upon mountain—serried, castellated, turreted, . ”

“ The igneous rocks are divided into two general classes,—the volcanic or eruptive rocks, which have been outpoured in open air or on the floor of the sea, and the intrusive rocks, which have been intruded within the rocks of the crust and have solidified below the surface. ”

“ And hence if the geologist would form an accurate conception of the origin and structure of many of the stratified rocks, he must study them not in hand specimens neatly trimmed and arranged along the shelves and drawers of a cabinet, nor even in the ponderous blocks daily exhumed by the quarryman, but along some surf-beaten cliff-line or down some precipitous ravine where the rock for centuries has been exposed to the wear and tear of the elements. ”

“ Mountains internally are principally composed of stone and rocks in parallel beds: between the horizontal beds small strata of a softer matter than stone is found, and the perpendicular clefts are filled with sand, crystals, minerals, metals, &c. these last matters are of a more modern formation than the horizontal beds in which we find sea-shells. ”

“ Imagine an instantaneous descent of granite-sand and gravel sufficient to smash and crush these trees to the ground, to bury their trunks, and to cover the earth one hundred to five hundred feet higher than the elevation to which their tops now reach! ”

“ Above our heads gigantic masses of rock towered upward, dark and menacing in their rugged strength, from whose crevices burst forth some withered-looking trees, which wreathed their distorted limbs into fantastic shapes around the huge blocks of stone to which they clung ”

“ There is a beautiful polished rock, about six feet square and quite thick, carved out like a basin and placed over this spring, to receive the clear, cool waters that constantly bubble up through the silver-sand. ”

“ Under the drift lie layers of stratified rock, and [Pg 56] under these are the granites and other fire-formed rocks, the beginning of those rock masses which form the solid bulk of the globe. We know little about the core of the earth, but the granites that are exposed in mountain ridges are found to have a great capacity for absorbing water, so it is not unlikely that much surface water soaks into the rock foundations and is never drained away into the sea. ”

“ I also had a clear view of the coast mountains for a hundred miles or thereabouts, all of which are tellingly glaciated in harmony with the above generalization. Most of the rock is granite with cleavage planes that cause it to weather rapidly into flat blocks. One conical black hill, fifteen hundred feet high, is volcanic rock, close-grained and dense like some kinds of iron ore. ”

“ The surface of the Earth is found to be covered with a series of irregular depressions or Basins, divided from one another, and sometimes wholly surrounded by projecting portions of subjacent strata, or by unstratified crystalline rocks, which have been raised into hills and mountains, of various degrees of height, direction and continuity. On either side of these more elevated regions, the strata dip with more or less inclination, towards the lower spaces between one mountain range and another. ”

“ The rock mantle and its shield in the mat of vegetation.—Through the action of weathering, the rocks, as we have seen, lose their integrity within a surface layer, which, though it may be as much as a hundred feet or more in thickness, must still be accounted a mere film above the underlying bed rock. The mechanical agents of the breakdown operate only within a few feet of the surface, and the agents of rock decomposition, derived as they are from the atmosphere, become inert before they have descended to any considerable depth. ”