Justin R. Loomis

“ Hence, whatever be the estimate which we form of the antiquity of the earth, from the slowness of denudation, or from the thickness of the strata, we must now add to that estimate the period elapsed since the creation of the human species.
We have seen that at different periods of the earth’s history different species of animals inhabited it. We are unable to fix with accuracy the ordinary duration of species. But the species which are now extinct probably had an existence as long-continued as will be enjoyed by species now living. ”

“ From the examples which have now been given, as well as from speculations upon the cause of these changes, it seems highly probable that all the surface of the solid portion of the earth, whether land or the bed of the sea, is undergoing changes of level. It may be so gradual that in the life of an individual it would be imperceptible, even where the best means of detecting it exist. These means are generally the works of man, and they are themselves so liable to change, that it would be scarcely possible to detect variations of level, which amount to but a few inches in a century. ”

“ If in any place there is absolutely no vertical movement, then those conditions must exist in which, for the time being, there is no change of temperature.
But it is doubtful whether there ever is absolute stability of any portion of the surface for long periods of time. Of the minor vertical movements of the interior of continents, there can, from the nature of the case, be no evidence whatever. Changes of level, where they are known to be taking place, are so slow, that they are hardly perceptible in the period of a human life. ”

“ And if the leading design of the existence of this earth was as a theatre for the development of moral character, it is to be presumed that the work of creation ceased when a species possessing moral capacities had been introduced. ”

“ The Subsidence of Land.—Elevations can be shown to have taken place by fossils, and by other evidences of former sea levels which are left on the surface; but depressions leave but few indications of change of level. It is yet doubtful whether the depression is equal to the elevation; that is, whether the amount of land remains nearly constant, or whether there has been an augmentation of the dry land within the tertiary and recent periods. We are certain that the augmentation, if any, has not been equal to the elevation, for subsidences to a great amount are known to have taken place. ”

“ The effects of all organic causes in producing geological changes are inconsiderable, compared with those of inorganic causes. With the exception of the coral formation, the most important of these effects are those produced by human agency. We find examples of this agency in the distribution of animals and plants beyond the regions where they are indigenous; in the increased numbers of certain species, and in the diminution, if not extinction, of others; in the modifications of climate, dependent on the destruction of the forests and the cultivation of the soil ”

“ In the valley of the Kenhawa river, Kentucky, the rocks of which belong to the carboniferous system, the brine is nearly saturated with salt; and in some of the borings they have even discovered beds of rock-salt of great thickness and purity.
There is no other part of the geological series so obviously connected with national prosperity as the coal formation. While a country is new, the forests furnish an abundant supply of fuel; but in the course of a few years these are consumed. This country will soon be principally dependent upon its coal-mines for fuel, even for domestic purposes ”

“ Each of these facts carries us back to a period immeasurably anterior to the creation of man, as the epoch when the sedimentary deposits commenced. There are no facts in geology which point to a different conclusion. It is of the utmost importance to the geological student to familiarize himself with this principle. It will assist him in comprehending the greatness of geological changes, and in applying other principles in explanation of geological phenomena. ”

“ Sediment is generally deposited as a soft mud, but in nearly all the older formations it has become solidified. When rocks are deposited from a chemical solution, they take at once the solid form. Such is the case with rock-salt and with limestone, when the material has been held in solution. Solidification takes place in nearly the same way when water which holds carbonate of lime or oxide of iron in solution filters through beds of sand or gravel. The substance held in solution is deposited in the interstices till they become filled, and the whole is changed to solid rock. ”

“ Moreover, the quantity of material which has been furnished by organic causes is by no means small. The coal-beds are the product of vegetable growth exclusively. We not unfrequently find strata of great extent consisting almost entirely of the shells of molluscous animals, of the stems of encrinites, or of the shields of microscopic animalcules.
But the most abundant rock which can be regarded as the product of animal organization is the coral formation. It consists of immense walls of coral limestone, separating either an atoll or the land of an island or continent from the open sea. ”

“ The lowest change of winch we can gain any information is the formation of granite. It will be shown hereafter that it has been in a melted state, and that it has taken its present form on cooling. But whether any considerable portions of the granitic masses, or of the melted masses now below the surface, have resulted from the fusion of stratified rocks, we have not the means of determining. It is, however, not improbable, that in the changes of level to which the crust of the earth has been subjected, the stratified rocks may have gone down so far as to become melted. ”

“ The lacustrine deposits can contain only fresh-water species of animals, marine deposits only marine animals, while deltas may contain the remains of marine life mingled with those which have been washed down by rivers. The remains of birds, insects, and terrestrial animals, may occasionally occur, in every kind of deposit. Sediment deposited in deep water will never contain fossils in abundance, the deep parts of the ocean being almost wholly destitute of animal or vegetable life. It is only in water of a few fathoms that the greater number of species and of individuals occur. ”

“ The waves also encroach upon the coast when it consists of rocks, even of the most indestructible kinds. They continually beat upon it, undermine the cliffs, and precipitate them into the sea. The tides increase the power of the waves, by varying the place of their action, so as to present the same surface of rock alternately to the action of water and of the air, frost and sun. During storms, the waves have sufficient force to break off fragments of rock from the escarpment, sometimes in masses weighing twenty tons or more, and remove them many rods inland. ”

“ Beds of vegetable matter, with a great thickness of rock deposited above them, would therefore be subject to all the conditions necessary to convert them into coal, namely, pressure from the superincumbent mass, and the heat which the strata uniformly assume at great depths.
It is not improbable, therefore, that coal-beds are now forming, and that they have been formed at every geological period since an abundant terrestrial vegetation commenced. Accordingly, there occurs in Virginia an extensive coal-field in the oölite formation. ”

“ We do not know at what depth below the surface of the earth the rocks become liquid; but above the line of actual fusion there must be a mass of rock not melted, yet scarcely retaining the solid form. For a great thickness, perhaps for several miles, it would be in a more or less yielding state. As there is not actual fusion, the stratification is not destroyed, [136] but such a degree of mobility among the particles exists, that some degree of crystallization takes place, and the elastic forces below easily bend, throw into folds, compress, and in every way contort these strata. ”

“ Hydrogen occurs in nature principally in combination with oxygen, forming water. It is also an ingredient in bitumen and bituminous coal.
Nitrogen is confined almost entirely to the atmosphere, of which it forms four-fifths. It enters into the composition of some varieties of coal, and is sparingly diffused in most fossiliferous rocks.
One of the most important substances in nature is carbon. It constitutes the principal part of all the varieties of coal, as well as of graphite, peat and bituminous matter. ”

“ It would seem that each species has a life assigned to it, which is to be completed and surrendered. Though its continuance is many times longer than the life of any individual of the species, yet it is the course of nature that species should disappear. ”

“ Even the most fluid lavas contain particles of minerals in a solid state. The liquidity depends upon the fusion of the more fusible portions, and upon the steam of water at a high temperature, which fills the interstices between the solid particles. The porous character of cooled lavas is produced by the steam which filled the cavities previous to solidification. Steam always escapes from the surface of a lava current while it is cooling, and it is always discharged in immense volumes from the orifice of eruption, in connection with the lava, and especially at the close of an eruption. ”

“ Knowing that heat and water exist at the volcanic centres, it is not difficult to form an idea of their mode of operation. The water, diffused through the interstices of the lava, and subjected to a temperature sufficient to melt the lava, would possess an elastic power, which, though never computed, we may well suppose capable of overcoming any resistance which the crust of the earth might present. The repressing force will be the tenacity and weight of the superincumbent strata. ”

“ As the accumulation of lava along the line of fracture is the cause of the upheaval, every mountain must have a central granitic axis. Sometimes this granitic mass is pushed up through the fissure, as in the case of Mont Blanc. At other times, the stratified rock, which formed the original surface, is carried up so as to form the surface rock nearly to the top. In either case, the strata are lifted along the line of fracture, and left in an inclined position. In this position the older rocks are always found, wherever there has been any considerable amount of igneous disturbance. ”

“ The general conclusion of a temperature sufficient to melt the mineral substances of which rocks are composed, at no considerable distance below the surface, is confirmed by the fact that portions of the interior of the earth—at least, at the volcanic centres—are in a melted state. ”

“ 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. ”

“ There may be something in the constitution of each species by which its continuance is limited, making an old age and death necessary, as it is in individuals. But there are other causes by which the duration of species may often be terminated. The subsidence of New Holland would cause the destruction of a large number of species. The preservation of the human species was at one time effected only by a special and miraculous interference. Slowly operating causes are now at work, by which many species, such as the elephant, wolf and tiger, will at length become extinct. ”

“ When granite or limestone contains sulphuret of iron, the oxygen of the atmosphere, in connection with moisture, combines with the sulphur, forming sulphuric acid, by which limestone and the felspar of granite are rapidly decomposed. Hence, a rock which contains an oxide or sulphuret of iron should not be used for architectural purposes.
Carbonic acid is another constituent of the atmosphere which operates as a decomposing agent. The water that falls from the atmosphere is charged with it, and thus becomes capable of dissolving [96] calcareous rocks. ”

“ The valleys descend rapidly towards the base of the mountains; and this snow-ice, having no cohesion between its particles, moves slowly down the slope of the valley, like a very imperfect liquid. After descending below the line of perpetual snow, the surface will melt during the day; and the water, sinking into the porous mass, becomes frozen, and converts the whole into more or less compact ice, yet never into a rigid mass. ”

“ As the animal species which inhabit bodies of fresh water are always different from those found in the sea, their remains constitute the best means of determining whether a formation is of fresh water or marine origin. ”

“ The force which the water acquires in its descent is such as to excavate a deep cavity at the foot of the fall, reaching back under the ledge from which the water descends. The ledge is therefore constantly being undermined. The cataract of Niagara is peculiar, in having the rock at its base of a soft and friable texture, so that it is rapidly worn away, while the upper rock is a compact siliceous limestone. If the order of superposition had been the reverse, the falls would have been converted into a series of rapids. ”

“ The force of the current alone, when it reaches the bottom, is, however, sufficient to remove every form of loose earthy matter. Thus it may be presumed that the Gulf Stream sweeps all the sediment from its bed until it reaches the latitude of Cape Hatteras, where the cold waters from the north begin to underlie it, and it takes the character of a surface stream.
But the transporting power of marine currents depends mostly upon the depth of water. It is found, by experiment, that ordinary river sediment will sink in water about one foot in an hour. ”

“ Most of these deposits have become solidified rock, such as limestone, clay slate and sandstone. The chalk of England is, however, but imperfectly consolidated, the great sandstone formation of New Holland is a friable mass easily disintegrated, and occasionally beds of clay in a plastic state are found as far down as the coal. Among the later rocks the solidification is less general, though there is some degree of hardening in all except the most superficial layers. The fissile structure results from the solidification of the particles composing each layer separately. ”

“ But there is no evidence from geology that man existed till after the close of the tertiary period. The grounds upon which contrary statements have sometimes been made are untenable. In Ohio a very perfect impression of a human foot was found on a slab of limestone of the silurian age. But it was subsequently ascertained to have been common for the aborigines, in the vicinity of their encampments, to cut in the rocks, with surprising accuracy, the forms of the tracks of man and other animals. ”

“ It is, however, susceptible of proof, that the present climates are not sensibly affected by interior heat, though at a little more than a mile below the surface the temperature is equal to that of boiling water. At any time, therefore, after the waters had become condensed, collected into oceans, and become sufficiently cool to support the animal life of which the remains are now found, it is not probable that the climate was, to any considerable extent, influenced by the heat conducted from the interior. ”

“ When crystalline, it has a pearly lustre, is transparent, and goes under the name of Selenite. Common Gypsum resembles the other earthy limestones, but it is softer, and may be readily distinguished by its not effervescing with acids.
To the minerals now enumerated may be added the following, which are of frequent occurrence, but not in great quantities; namely, carbonate of magnesia, oxide of iron, iron pyrites, rock-salt, coal, bitumen, schorl and garnet.
These simple minerals, either in separate masses or mingled more or less intimately together, compose almost wholly the earth’s crust. ”

“ The equatorial sea would absorb but a small proportion of the solar heat which would be thrown upon it. The land would receive the sun’s rays too obliquely to receive much elevation of temperature, as the present polar climates show. Hence, the temperature of the earth would differ but little from that of the planetary spaces, which is fifty-eight degrees below zero, a temperature too low to allow of any considerable development of organic life. ”