Subtropics

“ I hold that the sympathetic neutral flow which exists in this remote region is the latent power that, under the disintegration of water, is liberated; showing immense volume and infinite pressure. The same condition of latent power exists in metallic masses and, paradoxical as it may seem, exerts its force, under the proper exciter, only in a negative attractive way, while in water in a positive one. In minerals under liberation this latent power seeks its medium of tenuous equilibrium, leaving behind an impalpable dust, that represents molecular dissociation. ”

“ From the fact that the temperature of these wells and that of the mineral springs just east of them is said to be identical, and that they are, like the latter, never affected by surface-drainage, it is claimed that both have a common origin, and those that advocate the theory of sublimation claim that, if the waters are fresh at the site of these fresh-water wells, it is impossible for them to become mineral in their character by the short passage through the rocks that intervene between them and the fault; and hence they insist that the theory of percolation is untenable. ”

“ The depression and elevation of the solid or fluid parts of the earth — phenomena which are so opposite in their action that the effect of elevation in one part is to produce an apparent depression in another — are the causes of all the changes which occur in the configuration of continents. In a work of this general character, and in an impartial exposition of the phenomena of nature, we must not overlook the 'possibility' of a diminution of the quantity of water, and a constant depression of the level of seas. ”

“ The three conditions of flexure are time, heat, and pressure; and whenever the circumstances of a 84displacement include none of these, the rocks are broken. A fourth condition, moisture, is of great importance as an accessory, but alone it is not sufficient to prevent fracture. The whole body of strata of the earth’s crust is saturated with water, except a very little at the surface, and all rock movements are thereby facilitated. If the strata were dry, their flexure would require much more time, or heat, or pressure, than is necessary in their moist condition. ”

“ In the interior of the earth, where all knowledge of its chemical and mineralogical character fails, we are limited to as pure conjecture as in the remotest bodies that revolve round the sun. We can determine nothing with certainty regarding the depth at which the geological strata must be supposed to be in a state of softening or of liquid fusion, of the condition of fluids when heated under an enormous pressure, or of the law of the increase of density from the upper surface to the centre of the earth.”—Cosmos, vol. ”

“ That the earth at a certain depth may have been originally in a solid state; and, that, where it is to be consolidated, this is done by the mutual attraction of the stony particles. Here is all that we have been shown to make subterraneous heat, for the consolidation of strata, unnecessary; and now I humbly submit, if this is sufficient evidence, that mineral heat is a gratuitous supposition. ”

“ Does not the apparent wreck of the surface of this globe, thrown up into long ridges of mountains, with strata in various positions, make it probable, that its internal mass is a fluid; but a fluid so dense as to float the heaviest of our substances? Do we know the limit of condensation air is capable of? Supposing it to grow denser within the surface, in the same proportion nearly as it does without, at what depth may it be equal in density with gold? ”

“ TROPIC EQUILIBRIUM UNDER VARYING INTENSITIES OF STIMULUS.
The following experiment will show that the position of tropic equilibrium is not fixed but subject to variation under changes of effective stimulation.
Fig. 185.—Effect of variation of intensity of light on phototropic equilibrium. Increase of intensity of light from L to L' produces an increased positive curvature and a new state of balance. Diminished intensity of light l brings about a new balance at a lower level. The cessation of light (l within a circle) restores the normal position of the organ. ”

“ The nuclei may either be solid, or a high condensation of the atmospheres which surround each with decreasing density. When the attraction between the molecules is such that the elasticity of the atmospheres is insensible, the body is a perfect solid, the rigidity of which bears a certain definite proportion to the elasticity of the volume. When the atmospheres are less condensed and the attraction of the molecules merely produces a cohesive force sufficient to balance the atomic elasticity of the atmosphere, the body is a perfect liquid ”

“ It may be that there is a zone of matter beneath the structural rock and overlying the metallic nucleus which is penetrated by heat, now here, now there, and only these molten rocks are extravasated; or it may be that the solid state is limited by heat in one direction and by pressure in the other in such manner that all rocks flow under great pressure as do the metals. ”

“ The cause of this difference in the reactions to geotropic and other stimuli lies in the fact that in the latter case, energy is supplied from outside. But in geotropism the force of gravity is by itself inoperative; it is only through the weight of the cell contents that the stimulus becomes effective. Want of recognition of this fundamental difference has led many observers in their far-fetched and sweeping attempt, to establish an identity of reaction of the root to geotropic and photic stimulations, in spite of facts which plainly contradict it. ”

“ When elevation raises a portion of the earth's crust above sea-level, erosion and redeposition ensue and sedimentary rocks are formed; the greater the elevation the more energetically the forces act which bring about denudation, transportation, and sedimentation. When depression occurs of sufficient amount to carry rocks previously at or near the surface into the zone of metamorphism, alterations follow, and in general the deeper the depression the greater the changes until metamorphism culminates in fusion, providing pressure does not counteract the influence of heat. ”

“ We know that a change of temperature alters the position and the angles of the atoms of crystals, and also the entire bulk of rocks. We know that in all volcanic, and the greater part of all subterranean, action, temperatures are continually changing, and therefore masses of rock must be expanding or contracting, with infinite slowness, but with infinite force. This pressure must result in mechanical strain somewhere, both in their own substance, and in that of the rocks surrounding them ”

“ But if the air, when compressed, could be brought to the density of water, or wood to that of stone, there would be no need of any penetration of dimensions, and yet the compression would be much greater than they actually admit of. So if water could be expanded till it became as rare as air, or stone as rare as wood, there would be no need of a vacuum, and yet the expansion would be much greater than they actually admit of. ”

“ But the strained normal piling which surrounds the surface, and propagates with the surface, being of less density than the mean density of the medium, represents a displacement of the negative mass of the inequality, i.e., of the grains absent, and in whatever new direction the surface is propagating, the motion of the medium, outside the surface, is such as represents equal and opposite momentum, as when a bubble rises in water. ”

“ Lastly, the very curious result appears, that in a layer of fluid the particles are not equally distributed, nor do they all ever fall, under the influence of gravity, to the bottom. But just as the molecules of the atmosphere are so distributed, under the influence of gravity, that the density (and therefore the number of molecules per unit volume) falls off in geometrical progression as we ascend to higher and higher layers, so is it with our particles, even within the narrow limits of the little portion of fluid under our microscope. ”

“ But, of course, it must be understood that this would not happen if the body of water supposed were an isolated one and completely unconnected with other bodies of water through channels and intercommunications known to exist in the various ramifications of the earth's surface. The subterranean water circulation which interpenetrates the crust of the earth is clearly caused by the centripetal and centrifugal forces of nature, reënforced no doubt often by differences in temperature and other minor causes. ”

“ Metamorphism by heat and lateral pressure.—As already indicated, the more common intense pressures experienced by rocks at and near the surface are those that come from lateral thrusts arising from the shrinkage of the earth. These affect one dimension of the rock-mass, while they permit it to expand in one or both of the other dimensions. This produces a strain in all the constituent particles of the rock, and under such strain they pass more readily into solution than when free from strain, and more readily rearrange their molecules internally into positions of less strain. ”

“ This precision has not been used for the sake of the mechanical part of the problem, which does not require the surface to be defined with greater nicety than we can employ in our observations, but in order to give determinate values to the superficial densities of energy, entropy, and the component substances, which quantities, as has been seen, play an important part in the relations between the tension of a surface of discontinuity, and the composition of the masses which it separates. ”

“ But we know from observation that it is only within very small distances of such a surface that any mass is sensibly affected by its vicinity,—a natural consequence of the exceedingly small sphere of sensible molecular action,—and this fact renders possible a simple method of taking account of the variations in the densities of the component substances and of energy and entropy, which occur in the vicinity of surfaces of discontinuity. ”

“ It is a necessary result of the operation of the law of gravitation that the uppermost layer shall be the youngest and the lowest the oldest, and that the different beds shall be older at any particular point or spot in exactly the ratio of their depth from the surface. So that if they were upheaved afterwards, and you had a series of these different layers of mud, converted into sandstone, or limestone, as the case might be, you might be sure that the bottom layer was deposited first, and that the upper layers were formed afterwards. ”

“ Without entering into this difficult problem in physical geology, it may suffice if we carry with us the idea that our globe must once have had a greater diameter than it now possesses, and that the crumpling of its outer layers, whether due to mere contraction or, as has been suggested, to the escape also of subterranean vapors, affords evidence of this diminution. A little reflection suffices to show us that, even without any knowledge of the actual history of the contraction, we might anticipate that the effects would neither be continuous nor everywhere uniform. ”

“ Each of these sensible motions, produced directly or indirectly by integration of those insensible motions communicated from the Sun, becomes, as we have seen, divided and subdivided into motions less and less sensible; until it is finally reduced to insensible motions, and radiated from the Earth in the shape of thermal undulations. In their totality, these complex 455movements of aerial, liquid, and solid matter on the Earth’s crust, constitute a dependent moving equilibrium. As we before saw, there is traceable throughout them an involved combination of rhythms. ”

“ There are to be found, among the various strata of the globe, bodies formed of two different kinds of substances, siliceous bodies, and those which may be termed sulphureous or phlogistic. With one or other, or both of those we substances, every different consolidated stratum of the globe will be found so intimately mixed, or closely connected, that it must be concluded, by whatever cause those bodies of siliceous and sulphureous matter had been changed from a fluid to a concreted state, the strata must have been similarly affected by the same cause. ”

“ From the simple fact that the sphere is of all surfaces that whose surface-area for a given volume is an absolute minimum, we have already seen it to be plain that it is the one and only figure of equi­lib­rium which will be assumed under surface-tension by a drop or vesicle, when no other disturbing factors are present. One of the most important of these disturbing factors will be introduced, in the form of complicated tensions and pressures, when one drop is in contact with another drop and when a system of intermediate films or partition walls is developed between them. ”

“ The intensity of the centrifugal force will increase with the distance from the center of the earth, while gravity will decrease; the resultant will also increase. Thus, we find the strongest and most abundant overflows at the tops of mountains or on high plateaus. But suppose it had been fully proved that a particular overflowing spring was caused by hydrostatic pressure, it would still remain to be accounted for how the water got to that higher point. ”

“ The lower curve, PC, represents the interior pressures, ranging from one atmosphere at the surface to 3,000,000 atmospheres at the center, derived from Laplace’s law of density. The upper curve, FC, represents the fusion-points of diabase at the various depths and pressures, and hence the temperatures at which the interior would become solid at the various depths, or, in other words, the initial temperatures of the solid earth. ”