Earthwork

“ The required width of the formation must be principally regulated by the character of the earth, the amount and suddenness of the rainfall, the height of an embankment or depth of a cutting, the degree of exposure, the exigencies of the traffic, and the required drainage. ”

“ Geology, therefore, like all other natural sciences, is made up partly of fact, and partly of theory. It belongs to the Geologist first to investigate the phenomena which the Crust of the Earth exhibits to the eye. For this purpose he descends into the mine and the quarry; he visits the lofty cliff by the sea-shore, the deep ravine on 31 the mountain side, the cutting of a railway; in a word, every spot where a section of the Earth’s Crust is exposed to view, either by the action of Nature or by the hand of man. ”

“ Geology, or the natural history of the earth, as a planet revolving in space round a central orb of light and heat, surrounded by an atmosphere, and partially or wholly begirt by water, includes all the phenomena produced on the land, in the sea, and within the mass of the globe, by the operation of those mechanical, chemical, electrical, and vital forces, which are termed natural agencies, from the earliest epoch of which monuments remain, down to the present hour. ”

“ 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. ”

“ If the labour of the geologist were concerned merely with the former changes of the earth's surface—how sea and land have changed places, how rivers have altered their courses, how valleys have been dug out, and how mountains have been carved, how plains have been spread out, and how all these things have been written on the framework of the earth—he would still feel one very great want, the want of living interest. ”

“ Everywhere we may catch glimpses of a process of gradual change, which stretches backward into the past and forward into the future, by which the forms and structures of the face of the earth are continually built and continually destroyed. The science which deals with this long process is geology. Geology treats of the natural changes now taking place upon the earth and within it, the agencies which produce them, and the land forms and rock structures which result. ”

“ The detailed study of the work now being done by rain and rivers, underground water, waves and currents, the atmosphere, glaciers, changes of temperature, gravity, organic agencies and all other forces and activities operative on the surface of the earth has taught geologists how to interpret the rocks formed in ages long past. It is by the interpretation of the recorded results of the past, in the light of the processes now taking place, that the science of geology has grown up. ”

“ He who has observed the quarrying of stone from a rock, and has seen it shipped for some distant port, and then endeavors to conceive what kind of edifice will be raised by the materials, is in the same predicament as a geologist, who, while he is confined to the land, sees the decomposition of rocks, and the transportation of matter by rivers to the sea, and then endeavors to picture to himself the new strata which Nature is building beneath the waters. ”

“ The division of the general surface into land and water, as well as the diversified form of the land, the existence of mountains and low lands, and the consequent modifications of climate, the waterfalls, and the river-systems, constituting the drainage of continents, are all results of the process of upheaval.
2. A large part of the mineral substances employed for architectural and economical purposes are oceanic deposits, such as the marbles, slates, sandstones and mineral salt, and would have been inaccessible if they had not been elevated from the position in which they were formed. ”

“ The geological agencies which we have so far studied—weathering, streams, underground waters, glaciers, winds, and the ocean—all work upon the earth from without, and all are set in motion by an energy external to the earth, namely, the radiant energy of the sun. All, too, have a common tendency to reduce the inequalities of the earth’s surface by leveling the lands and strewing their waste beneath the sea. ”

“ Tilted and convoluted, broken and crushed by myriad earth-movements—scarred, furrowed, worn and degraded by — 348 — the frosts, the rains, the rivers, and the seas of countless ages—the rocks of our Continent are yet eloquent of design. Where the ignorant sees nothing save confusion and discord, the thoughtful student beholds everywhere the evidence of a well-ordered evolution. ”

“ A CENTURY OF GEOLOGY.—STEPS OF PROGRESS IN THE INTERPRETATION OF LAND FORMS
By HERBERT E. GREGORY The essence of physiography is the belief that land forms represent merely a stage in the orderly development of the earth’s surface features; that the various dynamic agents perform their characteristic work throughout all geologic time. The formulation of principle and processes of earth sculpture was, therefore, impossible on the hypothesis of a ready-made earth whose features were substantially unchangeable, except when modified by catastrophic processes. ”

“ But while thus culling freely from the dominions of other sciences, geology claims as its peculiar territory the rocky framework of the globe. In the materials composing that framework, their composition and arrangement, the processes of their formation, the changes which they have undergone, and the terrestrial revolutions to which they bear witness, lie the main data of geological history. It is the task of the geologist to group these elements in such a way that they may be made to yield up their evidence as to the march of events in the evolution of the planet. ”

“ Familiar formulas which express this idea are: "The present is the key to the past"; "Geography is the geology of to-day," etc. The forces or agencies which are now modifying the earth's surface, 300 such as the rending of rocks by changes of temperature and the action of frost, erosion and deposition by streams, the dash of ocean waves against the land, volcanic eruption, the chemical action of organic acids, movements producing upheaval and subsidence, etc., have been in action for geological eras, but their intensity has varied from time to time and from place to place. ”

“ Now, this is precisely what has been done in the construction and disposition of the several parts of our planet. The hardest matter is placed where it can subserve a beneficial end, on the bottom of the sea, the shores of a continent, the hills that border the valleys of a country. The framework of the globe is in itself of the most durable materials, and these materials have been all so arranged as to render the earth solid, fertile, and beautiful [90] diversity of climate, combined with diversity of soil, moisture, and shelter. ”

“ They ought, in fact, to have learned a good deal about the great forces which are continually modifying the surface of the globe, and what they have now to do is to study more particularly the results which have followed from the constant operation of those forces. We shall suppose, for example, that the teacher has described how rivers erode their channels, and waves tend to cut back a coast-line, and how the products of erosion, consisting of gravel, sand, and mud, are distributed along river-valleys and accumulated in lakes and seas. ”

“ They involve not only an acquaintance with the recent operations of Nature, but an extensive research into the history of former geological periods. The surface of every country is like a palimpsest which has been written over again and again in different centuries. How it has come to be what it is cannot be told without much patient effort. But every effort that brings us better acquainted with the story of the ground beneath our feet, and at the same time gives an added zest to our enjoyment of the scenery at the surface, is surely worthy to be made. ”

“ That of which we have here undoubted information, and that which I am labouring to generalise by comparing similar phenomena, such as are to be found over all the earth, is this, That the natural operations of the atmospheric elements decompose the solid rocks, break down the consolidated strata, waste and wash away those loosened materials of the mountains, and thus excavate the valleys, as the channels by which an indefinite quantity of materials are to be transported to the sea for the construction of future continents. ”

“ Men had for several generations explored the rocks that lie beneath their feet, and had, by laborious and patient effort, deciphered the marvellous history of organic and inorganic changes of which these rocks are [Pg 55] the record, before they seriously set themselves to study the story of the present surface of the land. And thus what was one of the earliest problems to interest mankind has been one of the latest to engage the attention of modern science. ”

“ The working geologist, dealing in the main with purely physical problems, has for his object to determine the material structure of the earth, and to investigate, as far as may be, the long chain of causes of which that structure is the ultimate result. ”

“ Finally, physical geography is permitted to spread over much the same ground from a natural-science standpoint, giving many additional and interesting facts and laws concerning zones, volcanoes, ocean-beds and currents, atmospheric phenomena, geologic history, etc. The same earth, the same lands and oceans, furnish the outline in each case, and we travel over the same ground three or four times successively, each time adding new facts to the original nucleus. ”

“ Think of the solid earth, with trees and houses, cities and countries, mountains and seas—think of the vast tracts of land in Asia, Africa, and America—and then picture the whole mass spinning like a top, and rushing along its annual course round the sun at the rate of nineteen miles every second. ”

“ It has been seen that igneous and aqueous agents have remodeled, from time to time, the physical geography of the globe. Can it admit of a doubt that changes in the physical structure of the earth’s surface will be accompanied with other changes in the organic productions of extensive areas? ”

“ The geologist views the earth as a body in process of continual change, its surface a heterogeneous mass of fragmental material; he reads, in the record inscribed on its stony pages, the story of past development through many successive stages of progress, each making the globe more fit for habitation by man ”

“ The principles of physical geology come first; the several chapters are arranged in what is believed to be a natural order, appropriate to the greatest part of our country, so that from a simple beginning a logical sequence of topics leads through the whole subject. The historical view of the science comes second, with many specific illustrations of the physical processes previously studied, but now set forth as part of the story of the earth, with its many changes of aspect and its succession of inhabitants. ”

“ The quantity of soil gained from the sea by these different modes of acquisition is, indeed, too inconsiderable to form an appreciable element in the comparison of the general proportion between the two great forms of terrestrial surface, land and water; but the results of such operations, considered in their physical and their moral bearings, are sufficiently important to entitle them to special notice in every comprehensive view of the relations between man and nature. ”

“ In like manner, when the geologist surveys the convexity of his own globe, he finds its solid covering composed of rocks and beds of all shapes and kinds, lying at every possible angle, occupying every possible position, and all of them, generally speaking, at the same distance from the earth’s centre. Every where we see what was deep brought into visible relation with what was superficial—what is old with what is new—what preceded life with what followed it. ”

“ For we know that there are operations now in progress, at great depths in the interior of the earth, by which both large and small tracts of ground are made to rise above and sink below their former level, some slowly and insensibly, others suddenly and by starts, a few feet or yards at a time ”

“ Geology, as will be seen from the preceding details, is among the most comprehensive of the sciences. It invades the province of every one of them, and lays them all under contribution while following out its own peculiar researches. A dry description of rocks, in their simple mineral qualities, does not limit or exhaust its ample resources. Botany, zoology, meteorology—a part, in short, of every branch of natural history, as well as chemistry, physics, and astronomy, are severally enlisted in its service, and all give interest and importance to its discursive investigations. ”

“ Home Geography, then, is the very first and most fundamental of all nature studies. Loam, sand, gravel, clay, boulders, quarry stone, coal and mineral rocks, can be brought into the house and school room. Out of these, with intelligent direction, little children can build up a miniature world that they can understand. ”