William Bower Taylor

“ If the attempts hitherto made by kinetic theorists to explain the tensile strength of a rope or of a chain by the pressure of a vis a tergo have been exceedingly lame and unsatisfactory, even the more direct examples of actual impact and propulsion are really as little serviceable to the hypothesis of contact action. If we have good reason to believe that the constituent molecules of a steel bar are actually separated by relatively large spaces of intense repulsion, — a fortiori must the physical impact of the most violent percussion be resolved into an action through a vacant space. ”

“ We are not at liberty to assume unknown and undemonstrated actions, entirely different in character from anything which has been actually observed or necessarily inferred. Great as is the credit due to Professor Challis, for instance, for his dexterous, persevering, and laborious efforts to develop his theory by the stern logic of mathematics the whole demonstration is vitiated by the unwarranted preliminary assumption of qualities and modes of action in the aether analogous to those of gases; as for example, that the pressure and the density are proportional. ”

“ The most plausible suggestion yet made by this school is that a single omnipresent fluid aether fills the universe; that by various motions of the nature of eddies, the qualities of cohesion, elasticity, hardness, weight, mass or other universal properties of matter are given to small portions of the fluid which constitute the chemical atoms; that these, by modifications in their combination, form, and motion, produce all the accidental phenomena of gross matter ; that the primary fluid by other motions, transmits light, radiant heat, magnetism, and gravitation ”

“ Every phenomenon of light points strongly to the conception of a solid rather than a fluid constitution of the luminiferous aether, in this sense, — that none of its elementary molecules are to be supposed capable of interchanging places, or of bodily transfer to any measurable distance from their own special and assigned localities in the universe. ”

“ I found that before a spot, whose surface is a square inch can be produced, a force exceeding one thousand pounds must be employed. When the experiment is made with thin glasses, they are often broken before any black spot is produced There is therefore an essential difference between mathematical and physical contact ; between the absolute annihilation of distance, and the actual pressure of adjoining bodies. We must grant that two pieces of glass are not in mathematical contact till they are exerting a mutual pressure not less than one thousand pounds per square inch. ”

“ But if in dynamic action a gaseous undulation of aether, with its existing co-efficient of inertia, is found to be so palpably inadequate to the known effect, on the other hand the elasticity must be assumed to be incomparably more active than the limit expressed by the actual velocity of a luminous undulation. If its rate of propagation be assumed to be very many millions of times more rapid than that of light, the inertia must be correspondingly reduced ”

“ It is impossible to conceive anything to act where it is not," are not merely quite irrelevant to scientific verity, but if gravely accepted as physical postulates, prove only to be positive obstructions to scientific investigation. Professor Challis has well said, " I do not admit that any metaphysical argument can be adduced either in support of or against a physical hypothesis. Meta-physics come after physics." ”

“ Here all kinetic theory fails: and there is then something in the world beside " inertia and motion." Until some rational analysis be discovered, we must accept the fact (in the language of Sir John Herschel) as an "ultimate phenomenon." And as we find that the molecules of all material substance resist compression with a force proportional in some high ratio thereto, we can only conceive that they are separated by an interval through which this repellant resistance is exercised. ”

“ Nor is there any ascertained fact to warrant the supposition that the aether is a reservoir of force, — in any other sense than that without the possession of intrinsic tension it would be incapable of transmitting energy. So far therefore as sober experience is accepted as our guide, we only know that a mechanical impulse of suitable character being committed to the aether, it is a faithful vehicle of energy, never adding to, and never abstracting from its charge. ”

“ In the next place, the hypothesis of undulations similarly fails. First, because the motion assumed is not a vera causa. If it be answered that an all-pervading aether and its system of undulations are otherwise established, by the large array of well-observed phenomena shown to be in exact accordance both in quantity and in quality with the mathematical deductions from such postulated undulations, the rejoinder is, that such undulations as have thus been established are demonstrably incapable of inducing anything in the slightest degree analogous to gravitation ”

“ Whereas the main business of natural philosophy is to argue from phenomena without feigning hypotheses, and to deduce causes from effects, till we come to the very first cause, which certainly is not mechanical." [8]
It has already been noticed that elasticity has proved a stumblingblock to every kinetic hypothesis. A system of molecular physics without this property would represent a chaos ; but a chaos destitute of energy. As Lam6 has well observed in his admirable treatise on the subject, " The role of Elasticity in nature is as important as that of Gravitation!" ”

“ Nor can even an analogue of the invention be found in the corpuscular theory of gases ; for in the latter case, the free path of the particle is assumed to extend only for the short distance between neighboring molecules, and by reason of incessant collision and deflection among the elements the hydro-dynamic pressure of the medium is equal in all directions, quite irrespective of the number or character of intervening obstructions: while the gravific or ultramundane corpuscle must ex hypothesi travel from infinity in a perfectly straight and undisturbed path to fulfill its appointed mission. ”

“ Nor is there any real difference in the conception of an aether having concentric increments of density outward, in which ordinary matter is buoyed, as it were, toward the center: a scheme in which every particle of matter finds itself in the midst of its own little spheres of rarefaction, and in which such center of aetherial rarity is supposed to blindly follow the flying stone in whatever direction hurled at the caprice of an idle boy. ”

“ Failing thus at every point, the hypothesis leaves still more inscrutable the origin of the undulation. The center of disturbance is supposed to be the vibrating material element; but the cause of the vibration is never stated. If innate tendency be the answer, never surely was a more mysterious " occult quality " attributed to matter in the history of human excogitations. Either misapprehending altogether, or quite ignoring the origin of thermal vibrations, the kinetic theorist not unfrequently appeals to the dynamical doctrine of heat as the type and the warrant of his assumptions. ”

“ Omitting then any further consideration of the statical method of explaining gravitation by pressure, we find that kinetic systems are essentially of two classes, the hypotheses of emissions or corpuscles, and the hypotheses of fluid undulations. It is proposed to show that no form of either hypothesis can satisfy the two Newtonian conditions of a scientific theory — verity and sufficiency. ”

“ And as this observed fact, by the multiplicity of instances in which no intermediate agent has yet been detected, or rendered rationally plausible, is generalized into an " induction," the burden of proof lies entirely "on the shoulders of those who with a keener vision through nature's veil, are ready to proffer hypotheses "without assumptions," and endless motions without the aid of " occult qualities." ”

“ Taking the case of a steel ball struck suddenly by a steel bat, the interval of distance between the first impression of the moving mall and its nearest approach to the ball, is sufficient to permit the acceleration of motion in the missile through every gradation, from zero to its full velocity. ”