Days and weeks passed. When the opportunity presented, I consulted Dr. W. B. Chapman, the druggist and student of science, regarding the nature of light and earth, who in turn referred me to Prof. Daniel Vaughn. This learned man, in reply to my question concerning gravitation, declared that there was much that men wished to understand in regard to this mighty force, that might yet be explained, but which may never become known to mortal man.
"The correlation of forces," said he, "was prominently introduced and considered by a painstaking scientific writer named Joule, in several papers that appeared between 1843 and 1850, and he was followed by others, who engaged themselves in experimenting and theorizing, and I may add that Joule was indeed preceded in such thought by Mayer. This department of scientific study just now appears of unusual interest to scientists, and your questions embrace problems connected with some phases of its phenomena. We believe that light, heat, and electricity are mutually convertible, in fact, the evidences recently opened up to us show—that such must be the case. These agencies or manifestations are now known to be so related that whenever one) disappears others spring into existence. Study the beautiful experiments and remarkable investigations of Sir William Thomson in these directions."
"And what of gravitation?" I asked, observing that Prof. Vaughn neglected to include gravitation among his numerous enumerated forces, and recollecting that the force gravitation was more closely connected with my visitor's story than perhaps were any of the others, excepting the mysterious mid-earth illumination.
"Of that force we are in greater ignorance than of the others," he replied. "It affects bodies terrestrial and celestial, drawing a material substance, or pressing to the earth; also holds, we believe, the earth and all other bodies in position in the heavens, thus maintaining the equilibrium of the planets. Seemingly gravitation is not derived from, or sustained by, an external force, or supply reservoir, but is an intrinsic entity, a characteristic of matter that decreases in intensity at the rate of the square of the increasing distance, as bodies recede from each other, or from the surface of the earth. However, gravitation neither escapes by radiation from bodies nor needs to be replenished, so far as we know, from without. It may be compared to an elastic band, but there is no intermediate tangible substance to influence bodies that are affected by it, and it remains in undying tension, unlike all elastic material substances known, neither losing nor acquiring energy as time passes. Unlike cohesion, or chemical attraction, it exerts its influence upon bodies that are out of contact, and have no material connection, and this necessitates a purely fanciful explanation concerning the medium that conducts such influences, bringing into existence the illogical, hypothetical, fifth ether, made conspicuous by Aristotle."
"What of this ether?" I queried.
"It is a necessity in science, but intangible, undemonstrated, unknown, and wholly theoretical. It is accepted as an existing fluid by scientists, because human theory can not conceive of a substance capable of, or explain how a substance can be capable of affecting a separate body unless there is an intermediate medium to convey force impressions. Hence to material substances Aristotle added (or at least made conspicuous) a speculative ether that, he assumed, pervades all space, and all material bodies as well, in order to account for the passage of heat and light to and from the sun, stars, and planets."
"Explain further," I requested.
"To conceive of such an entity we must imagine a material that is more evanescent than any known gas, even in its most diffused condition. It must combine the solidity of the most perfect conductor of heat (exceeding any known body in this respect to an infinite degree), with the transparency of an absolute vacuum. It must neither create friction by contact with any substance, nor possess attraction for matter; must neither possess weight (and yet carry the force that produces weight), nor respond to the influence of any chemical agent, or exhibit itself to any optical instrument. It must be invisible, and yet carry the force that produces the sensation of sight. It must be of such a nature that it can not, according to our philosophy, affect the corpuscles of earthly substances while permeating them without contact or friction, and yet, as a scientific incongruity, it must act so readily on physical bodies as to convey to the material eye the sensation of sight, and from the sun to creatures on distant planets it must carry the heat force, thus giving rise to the sensation of warmth. Through this medium, yet without sensible contact with it, worlds must move, and planetary systems revolve, cutting and piercing it in every direction, without loss of momentum. And yet, as I have said, this ether must be in such close contact as to convey to them the essence that warms the universe, lights the universe, and must supply the attractive bonds that hold the stellar worlds in position. A nothing in itself, so far as man's senses indicate, the ether of space must be denser than iridium, more mobile than any known liquid, and stronger than the finest steel."
"I can not conceive of such an entity," I replied.
"No; neither can any man, for the theory is irrational, and can not be supported by comparison with laws known to man, but the conception is nevertheless a primary necessity in scientific study. Can man, by any rational theory, combine a vacuum and a substance, and create a result that is neither material nor vacuity, neither something nor nothing, and yet an intensified all; being more attenuated than the most perfect of known vacuums, and a conductor better than the densest metal? This we do when we attempt to describe the scientists’ all-pervading ether of space, and to account for its influence on matter. This hypothetical ether is, for want of a better theory of causes, as supreme in philosophy to-day as the alkahest of the talented old alchemist Van Helmont was in former times, a universal spirit that exists in conception; and yet does not exist in perception, and of which modern science knows as little as its speculative promulgator, Aristotle, did. We who pride ourselves on our exact science, smile at some of Aristotle's statements in other directions, for science has disproved them, and yet necessity forces us to accept this illogical ether speculation, which is, perhaps, the most unreasonable of all theories. Did not this Greek philosopher also gravely assert that the lion has but one vertebra in his neck; that the breath of man enters the heart; that the back of the head is empty, and that man has but eight ribs?"
"Aristotle must have been a careless observer," I said.
"Yes," he answered; "it would seem so, and science, to-day, bases its teachings concerning the passage of all forces from planet to planet, and sun to sun, on dicta such as I have cited, and no more reasonable in applied experiment."
"And I have been referred to you as a conscientious scientific teacher," I said; "why do you speak so facetiously?"
"I am well enough versed in what we call science, to have no fear of injuring the cause by telling the truth, and you asked a direct question. If your questions carry you farther in the direction of force studies, accept at once, that, of the intrinsic constitution of force itself, nothing is known. Heat, light, magnetism, electricity, galvanism (until recently known as imponderable bodies) are now considered as modifications of force; but, in my opinion, the time will come when they will be known as disturbances."
"Disturbances of what?"
"I do not know precisely; but of something that lies behind them all, perhaps creates them all, but yet is in essence unknown to men."
"Give me a clearer idea of your meaning."
"It seems impossible," he replied; "I can not find words in which to express myself; I do not believe that forces, as we know them (imponderable bodies), are as modern physics defines them. I am tempted to say that, in my opinion, forces are disturbance expressions of a something with which we are not acquainted, and yet in which we are submerged and permeated. Aristotle's ether perhaps. It seems to me, that, behind all material substances, including forces, there is an unknown spirit, which, by certain influences, may be ruffled into the exhibition of an expression, which exhibition of temper we call a force. From this spirit these force expressions (wavelets or disturbances) arise, and yet they may become again quiescent, and again rest in its absorbing unity. The water from the outlet of a calm lake flows over a gentle decline in ripples, or quiet undulations, over the rapids in musical laughings, over a precipice in thunder tones,—always water, each a different phase, however, to become quiet in another lake (as ripples in this universe may awaken to our perception, to repose again), and still be water."
"Go on," I said.
"So I sometimes have dared to dream that gravitation may be the reservoir that conserves the energy for all mundane forces, and that what we call modifications of force are intermediate conditions, ripples, rapids, or cascades, in gravitation."
"Continue," I said, eagerly, as he hesitated.
He shook his head.