Stratification

“ 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. ”

“ Few, if any of us, understand thoroughly the nature of the unconscious stratification which takes place in life, the layers and types and classes into which it assorts itself and the barriers which these offer to a free migration of individuals from one class to another. ”

“ 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. ”

“ 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. ”

“ To illustrate this, let the subjoined diagrams represent portions of clay slate and grauwacke slate, alike in all respects of structure, except the nature and direction of the lamination, D being in each a plane of stratification. In grauwacke slate (No. 37.) the laminæ of deposition show on all the vertical planes, being all parallel or nearly so to the plane of stratification; in clay slate laminæ of deposition are not seen ”

“ Indeed when it is considered, that in France much more frequent opportunities are afforded of examining the stratification immediately above the chalk than in England, it will not be regarded as improbable, that several of these beds or patches may exist here, the discovery of which would render the accordance of the two series of strata much more close. ”

“ 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. ”

“ 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. ”

“ It was remarked that the same species of organic remains cannot be traced horizontally, or in the direction of the planes of stratification for indefinite distances. This might have been expected from analogy; for when we inquire into the present distribution of living beings, we find that the habitable surface of the sea and land may be divided into a considerable number of distinct provinces, each peopled by a peculiar assemblage of animals and plants. In the Principles of Geology, I have endeavoured to point out the extent and probable origin of these separate divisions ”

“ 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. ”

“ What stratification is to mountains whose geological formation is the same throughout, the superposition of [153] different kinds of rocks is to those of composite materials. The layers may be divided into superior, inferior, and adjacent. These usually vary in respect to age, and may be traced in a regular geological seniority, as for example sandstone, gypsum, limestone, gray-wacke, and granite. ”

“ 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 ”

“ 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! ”

“ 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? ”

“ 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. ”

“ 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. ”

“ 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. ”

“ The solution of an old geological problem requires far more caution than the explanation of a modern geographical phenomenon. For in regard to the older events we are seldom aware of all the essential facts, from which not only the nature of the physical agency is to be ascertained, but the measure of its force, the local centre of its effect, and the sudden or gradual, the continuous or interrupted mode of its application. The geographical relations of tertiary strata must be understood before venturing to adopt or to reject the hypothesis of partial elevation and subsidence. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ Differentiation and isolation.
Differentiation results not only from contrasted geographic conditions, but also from segregation. A moving or expanding throng in search of more and better lands drops off one group to occupy a fertile valley or plain, while the main body goes on its way, till it reaches a satisfactory destination or destinations. The tendency to split and divide, characteristic of primitive peoples, is thus stimulated by migration and expansion. ”

“ Permanent settlement encourages accumulation in every form, and under growing pressure of population slowly reveals the possibilities of every foot of ground, of every geographic advantage. These are the fibers of the land which become woven into the whole fabric of the nation's life. ”

“ The binary or dichotomous system, although it brings out the fundamental differences of the respective regions, is an inconvenient one in its application, and rather increases than obviates the difficulty as to equality or inequality of regions; for although a, b, c, and d, may be areas of unequal zoological rank, a being the most important, and d the least, yet this inequality will probably be still greater if we first divide them into a, on one side, and b, c, and d, on the other, and then, by another division, make b, an area of the second, and c, and d, of the third rank only. ”

“ Even supposing, however, that districts some hundreds of miles apart, furnished groups of strata that completely agreed in their order of superposition, their mineral characters, and their fossils, we should still have inadequate proof of contemporaneity. For there are conditions, very likely to occur, under which such groups might differ widely in age. ”

“ As might have been expected, however, in an attempt to divide great areas that have not even been mapped, and with an economic value still to be determined, the boundaries of the spheres are oftentimes indefinite, and instead of settling disputed questions, but defer them to the generations yet to come. ”

“ In a single district it is difficult to decide how far the limitation of species to certain minor formations has been due to the local influence of stations, or how far it has been caused by time or the law of variation above alluded to. ”

“ The very origin and persistence of the cumbersome common-field system in so many parts of the world is sufficient testimony as to the impossibility of improving the quality of the soil in the Middle Ages. The only way in which these men could divide the land into portions of equal value was to divide it first into plots of different qualities and then to give a share in each of these plots to each member of the community. ”

“ It is clear, therefore, that amidst all the causes of local diversity in the series of strata, some general influences have prevailed to give a determinate analogy of character to the resulting succession of stratified rocks in all parts of the globe If we can search out the causes of local diversity and general agreement, and thus ascertain the law of the geological scale of time, nothing will remain to be done but the comparison of this law with the analogous operations of modern nature, in order to attain the most precise account of geological time which the human mind can reach. ”

“ The proper investigation of a formation can no more overlook development than structure, so closely are the two interwoven. Future research must rest squarely upon this fact.
249. Functions and structures. The functions of a formation are association, invasion, and succession: the second may be resolved into migration and ecesis, and the third, perhaps, into reaction and competition. Formational structures comprise zones, layers, consocies, societies, etc., all of which may be referred to zonation, or to alternation. The term association 200has been used in both an active and a passive sense. ”

“ Small naturally defined regions, which take the lead in historical development because they counteract the primitive tendency towards excessive dispersal, are in danger of teaching too well their lesson of concentration. In course of time geographic enclosure begins to betray its limitations. The extent of a people's territory influences their estimate of area per se, determines how far land shall be made the basis of their national purposes, fixes the territorial scale of their conquests and their political expansion. This is a conspicuous psychological effect of a narrow local environment. ”