Stratagem

“ And here indeed we may see very simply illustrated, the truth, which we shall presently have to trace out in more involved cases, that in proportion to the heterogeneity of the object or objects on which any force expends itself, is the heterogeneity of the results. A continent of 38 complex structure, exposing many strata irregularly distributed, raised to various levels, tilted up at all angles, must, under the same denuding agencies, give origin to immensely multiplied results; each district must be differently modified; each river must carry down a different kind of detritus ”

“ A succession of strata indicates a succession of time for their formation; and the change from one species of stratum to another placed upon it, indicates a change of cause. Thus is the mass of our continents the product of successive operations, during which the producing causes have undergone successive changes. We see, moreover, that many of these strata contain the remains of animals; and that in some successive strata these organized bodies are of different species. ”

“ The strata being found as regular on one side of a rivulet, river, deep valley or channel as on the other, over an extent of many miles, when proper allowance is made for the inclination, and for the variation of the surface, is it not reasonable to suppose that the same strata may be found as regular on one side of the sea or ocean as on opposite sides of a deep valley upon land, and if so, and the continuation of the strata is general, what is their general direction or drift? ”

“ In the more level parts of Navarin Island, these bands of stratification were nearly horizontal; but on the flanks of the mountains they were inclined from them, but in no instance that I saw at a very high angle. There can, I think, be no doubt that these zones, which appear only on the weathered surfaces, are the last vestiges of the original planes of stratification, now almost obliterated by the highly fissile and altered structure which the mass has assumed. ”

“ Whenever, in any district, the stratified rocks, instead of all lying parallel to one another, suffering the same deviations from horizontality, bending in the same flexures, dropping or rising by the same faults, and regarding in their declinations the same axis or centre of dips, divide themselves, in these respects, into two or more sets, which differ from one another in all or any of these respects, there is said to be unconformity of the strata. ”

“ When we desire to classify, it is necessary to contemplate entire groups of strata in the aggregate; but if we wish to understand the mode of their formation, and to explain their origin, we must think only of the minute subdivisions of which each mass is composed. We must bear in mind how many thin leaf-like seams of matter, each containing the remains of myriads of testacea and plants, frequently enter into the composition of a single stratum, and how vast a succession of these strata unite to form a single group! ”

“ First, it will account equally for the position of those elevated masses of marine origin in which the stratification remains horizontal, and for those in which the strata are disturbed, broken, inclined, or vertical. Secondly, it is consistent with human experience that land should rise gradually in some places and be depressed in others. ”

“ In such conglomerates there is usually no division into beds; the whole mass, indeed, forms a bed between lower and higher strata, but internally it shows for the most part no trace of stratification. ”

“ Now, according to the present theory, where the strata consolidated at the bottom of the sea are supposed to be erected into the place of land, we cannot suppose any valley formed by another agent than the running water upon the surface, although the parts which are first to be washed away, and those which are to remain longest, must be determined by a concurrence of various circumstances, among which this converging declivity of the strata in the bordering mountains, doubtless, must be enumerated. ”

“ It still is like an estuary in which the conflict of opposing tides brings to the surface what had just lain at the bottom, and drives to the bottom the bead that had glistened for a moment on the brimming top; in a word, social stratification is not yet complete among us. ”

“ We are bound to allow millions of years for the formation of the strata that have been already examined. There may be depths below the lowest depths yet explored by geologists; there have certainly been immense intervals which have left no materials for the geologist to explore; and when all the profoundest deep of stratification shall have been explored, we may still find that the record of all these unnumbered millions of years is but, as it were, the latest page of the volume—a page that may have been preceded by a thousand others now almost irrevocably lost or become utterly illegible. ”

“ The divide is thus a sort of boundary wall separating the drainage basins of neighboring streams, and any migration must extend the territory of the one at the expense of the other. As more and more territory is brought under the dominion of the more favored stream, there will come a time when the divide in its migration will arrive at the channel of the stream that is being robbed, and so by a sudden act of annexation draw off all the upper waters into its own basin. ”

“ Many, indeed most, of these strata contain the remains of animals which were living in the water at or before the time of the deposition of the rocks, and several are full of plants which were swept down from the dry land on which they grew into the ancient ocean, and then entombed in the strata at that epoch in progress of formation. ”

“ It is true that different strata not only may, but must have been forming at one and the same time in different parts of the world. But when one stratum has been formed out of the wreck of another, it is self-evident that they cannot have been formed together. The same thing is obvious in regard to any number of layers found lying in undisturbed succession one above the other. ”

“ If one desires to know the history of a region, one turns naturally to its mountain ranges, for here may be found the upturned and dissected strata, a study of whose kinds, thickness, and fossils throws light upon past events, while their foldings and dislocations show the nature and results of those great dynamic agencies which, from time to time, have operated upon the outer portion of the earth, and given to it the broad distinctive features which characterize it to-day. ”

“ But an experienced geologist can rarely be deceived by these exceptional cases. When he finds that the strata are fractured, curved, inclined, or vertical, he knows that the original order of superposition must be doubtful, and he then endeavours to find sections in some neighbouring district where the strata are horizontal, or only slightly inclined. Here, the true order of sequence of the entire series of deposits being ascertained, a key is furnished for settling the chronology of those strata where the displacement is extreme. ”

“ At present the most important things taught us by the phenomena of dipping strata are these:—1. The dip is related to the elevation of ground; and 2. The strata do not descend from one mountain chain below the surface of plain countries more than a very moderate depth (four to five miles) before they begin to rise again toward another axis of elevated ground.
The principal mountain chains and groups are thus seen to be the axes of declination of the stratified rocks ”

“ Like the successive geological formations, the tribes of [Pg 500] mankind may be arranged, according to their relative conditions, into successive strata. When thus arranged, they reveal with some degree of certainty the entire range of human progress from savagery to civilization. A thorough study of each successive stratum will develop whatever is special in its culture and characteristics, and yield a definite conception of the whole, in their differences and in their relations. When this has been accomplished, the successive stages of human progress will be definitely understood. ”

“ The strata inclined in every direction and describing the most capricious and picturesque forms, both curved and angular, open an abundant field of instruction to the geologist, while they present difficulties of which neither the theory of original deposition on an unequal surface, or of subsequent dislocation, appear to promise any plausible solution. ”

“ In many places where a vertical section is exposed to view, the phenomenon of stratification may be distinctly recognized. The upper part of the deposit belonging to each year is composed of earth of a lighter color than the lower part; and the whole forms a distinct layer of hardened clay, which may be easily separated from those above and below. This formation, therefore, corresponds exactly with those strata of shale which we so often meet with in the Crust of the Earth. ”

“ If the covering strata were all of a given thickness, were identical in kind, and were free to slide upon each other without friction, their total resistance to deformation would be equal to the resistance of a single stratum multiplied by the number of strata. But since they are not free to slide one upon another, they sustain each other, and the resistance offered by the combination is greater than that product. ”

“ If we look closer into the structure we find that it is based on the relation between the plough-team and the arable, a relation which is more or less constant and explains the gradations and the mode of apportionment. The division of the land is no indefinite or capricious one, because the land has to be used in certain quantities, and smaller quantities or fractions would disarrange the natural connexion between the soil and the forces that make it productive. ”

“ Ethnology reveals an east and west stratification of linguistic groups in Europe, a north and south stratification of races, and another stratification by altitude, which reappears in all parts of the world, and shows certain invading dominant races occupying the lowlands and other displaced ones the highlands. This definite arrangement points to successive arrivals, a crowding forward, an intrusion of the strong into fertile, accessible valleys and plains, and a dislodgment of the weak into the rough but safe keeping of mountain range or barren peninsula, where they are brought to bay. ”

“ The older the strata are, the more uniform is each of them over a great extent; the newer they are, the more limited are they, and the more subject to vary at small distances. Thus the displacements of the strata were accompanied and followed by changes in the nature of the fluid, and of the matters which it held in solution; and when certain strata, by making their appearance above the waters, had divided the surface of the seas by islands and projecting ridges, different changes might take place in particular basins. ”

“ Besides the negative evidence here afforded in support of our classification, it is sustained by the circumstance that these mounds are almost invariably found within enclosures, which, for a variety of concurring reasons, we are induced to believe were sacred in their origin, and devoted primarily, if not exclusively, to religious purposes. The circumstance of stratification, exhibiting as it does an extraordinary care and attention, can hardly be supposed to result from any but superstitious notions. ”

“ Stratification.—All rocks formed by strewing materials in water, and their deposition in successive, parallel, horizontal layers, are stratified; and this structure is their stratification. It is the most important of all rock structures; and there is no kind of structure the origin of which is more fully or certainly known. The deposition of sediment in carefully assorted horizontal layers is readily brought within the comprehension of children by simple experiments with sand and clay in water ”

“ We observe that the position of strata is almost universally horizontal: in plains it is exactly so, and it is only in the mountains that they are inclined to the horizon, from their having been originally formed by a sediment deposited upon an inclined base. ”

“ Intrusion of Trap between Strata.—Masses of trap are not unfrequently met with intercalated between strata, and maintaining their parallelism to the planes of stratification throughout large areas. They must in some places have forced their way laterally between the divisions of the strata, a direction in which there would be the least resistance to an advancing fluid, if no vertical rents communicated with the surface, and a powerful hydrostatic pressure were caused by gases propelling the lava upward. ”

“ When strata are crumpled up they naturally crack across, for they are not elastic. During the great movements which have originated — 52 — all mountains of elevation, it is evident that the strata forming the actual surface of the ground would often be greatly fissured and shattered along the crests of the sharper anticlinal ridges. ”

“ The continual process of undermining by the decay of the lower strata has caused periodical disruption of the hard upper stratum, which has fallen off in huge blocks and rolled down the rough inclines that form the sides. ”

“ We may consider the history of secondary, and also of tertiary strata, in two points of view: the one, respecting their actual state as dry land, destined to be the habitation of man; the other, regarding their prior condition, whilst in progress of formation at the bottom of the waters, and occupied by crowds of organic beings in the enjoyment of life. ”

“ But there
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are no continuous layers reaching over any large extent of country.
Sometimes the material has been subsequently worked over by rivers, and been distributed over limited areas in strata, as in and around the beds of streams.
But in the lower, older, and first-laid-down portion of the Drift, called in Scotland "the till," and in other countries "the hard-pan," there is a total absence of stratification. ”