Physical medium

“ Here then we have the basis of a view in which there are not two media to be considered, but one medium, homogeneous in essence and differentiated as regards its parts only by the presence of nuclei of intrinsic strain or motion—-in which the physical activities of matter are identified with those arising from the atmospheres of modified aether which thus belong to its atoms. ”

“ Nature may reach the same result in many ways. Like a wave in the physical world, in the infinite ocean of the medium which pervades all, so in the world of organism:, in life, an impulse started proceeds onward, at times, may be, with the speed of light, at times, again, so slowly that for ages and ages it seems to stay; passing through processes of a complexity inconceivable to men, but in ;ill its forms, in all its stages, its energy. ever and ever integrally present. ”

“ But, if the knowledge of the chemical and physical properties of the bodies which surround us, as well as our imperfect acquaintance with the less tangible elements, light, electricity, and heat, which mysteriously modify or change their combinations, concur to convince us of the same fact ”

“ That science which investigates the principles, upon which the action of every machine depends; and teaches their proper application in overcoming resistance, and in producing motion, in all the useful purposes to which they are applied.
Medium. In optics, is any body which transmits light. Air, water, glass, and all other transparent bodies, are media. Medium also denotes that in which any body moves. Air is the medium which conveys sound, and which enables birds to fly. ”

“ You are in the prime of life, in the beginning of your career, and you have powers and acquirements capable of illustrating and extending every branch of physical enquiry; and, in the field of science, how many are the spots not yet cultivated! Where the laws of sensible become connected with those of insensible motions, the mechanical with the chemical phenomena, how little is known! In electricity, magnetism, in the relations of crystallized forms to the weight of the elements of bodies, what a number of curious and important objects of research! ”

“ By it we find that the air has weight and pressure, color, density, elasticity, compressibility, and some other properties with which we shall endeavor to make the young reader acquainted by many pleasing experiments, earnestly impressing upon him to lose no opportunity of making physical science his study. ”

“ To emphasize the importance of a solid grounding in basic physical principles, we have tried to have our problems touch on most of the general 40 areas of physics: mechanics, heat, sound, light, electricity and magnetism, electronics, the properties of matter, atomic physics, physics of the solid state. ”

“ Now the state, including the shape or form, of a portion of matter, is the resultant of a number of forces, which represent or symbolise the manifestations of various kinds of energy; and it is obvious, accordingly, that a great part of physical science must be understood or taken for granted as the necessary preliminary to the discussion on which we are engaged. ”

“ Having now defined the use of the term force, and shown that forces are correlated which are convertible 44and mutually dependent, we go on to study the evidences of such correlation among the motions of inorganic nature usually called physical forces; and to ask what proof science can furnish us that mechanical motion, heat, light, and electricity are thus mutually convertible. ”

“ First of all the inquiry, by the aid of the microscope and electrical instruments of precision, into the nature of our organs and senses, and particularly of those through which we commune directly with the outside world and through which knowledge is conveyed to our minds, has revealed their exact construction and mode of action, which is in conformity with simple and well established physical principles and laws. Hence the observations we make and the facts we ascertain by their help are real facts and observations, and our knowledge is true knowledge. ”

“ The position which I seek to establish in this essay is, that the various imponderable agencies, or the affections of matter which constitute the main objects of experimental physics, viz., heat, light, electricity, magnetism, chemical affinity, and motion, are all correlative, or have a reciprocal dependence;—that neither, taken abstractedly, can be said to be the essential or proximate cause of the others ”

“ For example, the fact that we can distinguish cubes of equal size but of different material, different temperature, and different luminosity, can be traced back always and entirely to the different kinds of energy acting in the geometric space in question. The concept of energy, therefore, plays approximately the same rôle in the physical sciences as the concept of thing in the formal sciences, and the essentials of this new field of science are the comprehensive knowledge and development of this concept. ”

“ If it does not possess the most fundamental characteristic of matter, how can it possess such derived properties as density and elasticity,—properties which any conceivable mechanical medium must have in order to transmit transverse vibrations? ”

“ And the whole circle of the Physical Sciences, or Physical Science in its widest extent, confines itself to explaining the appearances of the material world by the properties of matter, and to reducing what is complex and manifold to the operation of a few simple but all-pervading laws. ”

“ I mean in just the same sense as the researches of physical philosophers have shown that heat is convertible into electricity, that electricity is convertible into magnetism, magnetism into mechanical force or chemical force, and any one of them with the other, each being measurable in terms of the other,—even so, I say, that great law is applicable to the living world. ”

“ It seeks for the first and best explanation of organic beings in the mere mechanical effects of their surroundings. The physical forces which act upon them from outside—the water or the air that bathes them—the impacts of ethereal undulations in the form of light, the vibrations of matter in contact with them in the form of heat—these are conceived of as the agencies principally concerned. ”

“ How strangely it obeys the impulses of heat—mysterious are the influences of light upon it—electricity wonderfully excites it—and still more curious [Pg 3] is the manner in which it obeys the magic of chemical force. These are phenomena which we have seen; we know them, and we can reproduce them at our pleasure. We have advanced a little way into the secrets of nature, and from the spot we have gained, we look forward with a vision somewhat brightened by our task ”

“ Every form, whether inorganic or organic, which we can discover within the limits of human search, is composed of atoms, which are capable of assuming, under the influence of certain physical forces, conditions essential to the physical state of that body of which they constitute a part. [1] The known forces, active in pro [Pg 5] ducing these conditions, are modes of motion; gravitation and aggregation, heat, light; and associated with these, actinism or chemical radiation; electricity, under all its conditions, whether static or dynamic ”

“ But our usual scientific custom of interpreting hidden molecular events after the analogy of visible massive ones enables us to frame easily an abstract and general scheme of processes which the physical changes in question may be like. And when once the possibility of some kind of mechanical interpretation is established, Mechanical Science, in her present mood, will not hesitate to set her brand of ownership upon the matter, feeling sure that it is only a question of time when the exact mechanical explanation of the case shall be found out. ”

“ Although we discover, in all the processes of nature, the manifestations of this principle or force in its characteristic conditions, it will be necessary, before we regard the great phenomena, to examine the known sources from which we can most readily evoke the mighty power of electricity. If we rub a piece of glass or resin, we readily render this agent active; these substances appear, by this excitement, to become surrounded by an attractive or a repellent atmosphere. ”

“ Let the fifteenth motion be that of transmission or of passage, by which the powers of bodies are more or less impeded or advanced by the medium, according to the nature of the bodies and their effective powers, and also according to that of the medium. For one medium is adapted to light, another to sound, another to heat and cold, another to magnetic action, and so on with regard to the other actions. ”

“ If we wished to represent to ourselves, by the mechanical properties of a medium filling the whole of the universe, all luminous, electric, and gravitation phenomena, we should be led to attribute to this medium very strange and almost contradictory characteristics ”

“ From the descriptions given above, it will be amply evident that each of these processes, whether transformation or transmission, requires as an essential condition of its existence, the presence of a certain arrangement of matter; each process is of necessity associated with and embodied in a definite physical and material machine. This material machine is simply the contrivance provided by Nature to carry out the energy operation. ”

“ Heat, electricity, chemical power—whatever that may be—and the forces of cohesion, are known to be involved in the production of the forms we see; but contemplation soon leads to the conviction that these powers are subordinate to others which we know not of. We know only the things belonging to the surface of our planet, and these but superficially. ”

“ The lectures in physical science embrace nine lectures on the general properties of bodies; heat, climate, electricity, magnetism, galvanism, electro-magnetism, acoustics.
There are twelve lectures in chemistry; on water, atmospheric air, combustibles, gas, principal salts, saltpetre, metallurgy, organic chemistry. ”

“ The wants imposed by its surroundings create certain organs in science. The problems set to physicists by the engineer who wishes to facilitate transport or to produce better illumination, or by the doctor who seeks to know how such and such a remedy acts, or, again, by the physiologist desirous of understanding the mechanism of the gaseous and liquid exchanges between the cell and the outer medium, cause new chapters in physics to appear, and suggest researches adapted to the necessities of actual life. ”

“ The development of physics on the speculative side has led, then, to the idea, gradually become more definite and fixed, of a universal medium, the existence of which is a matter of inference. To this medium properties have been assigned which are such as to enable us to form an intelligible, consistent conception of the mechanism by means of which phenomena, the mechanics of which is not capable of direct observation, may be logically considered to be produced. ”

“ Units of matter, solid, liquid, aëriform, or ethereal, filling the space which any moving body traverses, offer to such body the resistance consequent on their cohesion, or their inertia, or both. In other words, the denser or rarer medium which occupies the places from moment to moment passed through by such moving body, having to be expelled from them, as much motion is abstracted from the moving body as is given to the medium in expelling it from these places. ”

“ Dynamical agents.—The principal agents that are supposed to be concerned in giving circulation to the atmosphere, and in preserving the ratio among its components, are light, heat, electricity, and perhaps magnetism. ”

“ Evidently, then, the tendency of chemical investigation is to connect the physical properties of every substance directly with its composition.
Here we step over the border into physics. Plainly, if we have to deal with physical properties, we must study the forces represented by them. And, fortunately for the chemist, the tendency among physicists is entirely in his favor. Growing up contemporaneously with the development of chemical notation, we have had the grand ideas of the conservation of energy and the correlation of forces. ”

“ But the physical phenomena of contraction, expansion, absorption, undulatory and vibratory motions accompanying our sensations of light, heat and sound, as well as many other physical phenomena, all point to the fact that volumes of matter which are apparently continuous are really porous: the molecular structure of perceptible matter is an accepted physical theory ”

“ Here materialism calls to its aid the discovery of the correlation and equivalence of forces, one of the most stupendous achievements of our century. We now know that heat and light [Pg 68] and electricity and actinism are not forces generically distinct and isolated each from the others. All are specific modes of molecular motion, transformable one into another at any moment as naturally as a cloud condenses into raindrops. ”

“ Chemistry and physics were by no means inferior to mechanical science; they composed and decomposed bodies, transformed and melted them one into another, created new ones by bold combinations, produced heat, light, and energy. ”

“ Every condition of organised forms is due to the external excitation of light and heat, and in the chemical changes which take place, an equivalent of these principles, or powers—it signifies but little according to which view we may regard them—is absorbed, and retained as essential to the condition of the matter formed. ”

“ Hence, if we remember that the ultimate object of all physical science is the successful formulation of such practical rules for action, we can see that it is a logical consequence of the character of the interests which dominate our scientific descriptions, that the physical sciences should adopt a rigidly mechanical view of the physical order. ”

“ A medium of some sort pervading space seems also necessary to our theory. In fine, a universe composed of atoms, with some sort of medium between them, is to be regarded as the machine, and the laws of energy as the laws of working of this machine. ”