ÆTHER, the name of an imaginary fluid, supposed by several authors, both ancient and modern, to be the cause of gravity, heat, light, muscular motion, sensation, and, in a word, of every phenomenon in nature. Anaxagoras maintained that æther was of a similar nature with fire; Perrault represents it as 7200 times more rare than air; and Hook makes it more dense than gold itself. Whoever has an inclination to know the various hypotheses concerning æther, may consult Shebbere, Perrault, Hook's posthumous works, At. Erud. Lipf. 1716, Bernoulli's Cogitat. de gravitate ætheris, &c. &c.
Before the method of philosophising by induction was known, the hypotheses of philosophers were wild, fanciful, ridiculous. They had recourse to æther, occult qualities, and other imaginary causes, in order to explain the various phenomena of nature: But since the days of the great Lord Verulam, who may be styled the parent of genuine philosophy, a contrary course has happily been followed. He convinced the world, that all knowledge must be derived from experiment and observation; and that every attempt to investigate causes by any other means must be unsuccessful. Since his time, the best philosophers have followed the tract which he pointed out. Boyle, Locke, Newton, Hales, and a few others, in little more than one century, have improved and extended science far beyond what the accumulated force of all the philosophers since the creation had been able to effectuate: A striking proof both of the comprehensive genius of Bacon, and of the solidity of his plan of investigation.
It must indeed be acknowledged, that there is a propensity in the human mind, which, unless it be properly restrained, has a direct tendency both to corrupt science, and to retard our progress in it. Not contented with the examination of objects which readily fall within the sphere of our observation, we feel a strong desire to account for things which, from their very nature, must, and ever will, elude our researches. Even Sir Isaac Newton himself was not proof against this temptation. It was not enough that he had discovered the nature of light and colours, the application of gravity to the motions of the heavenly bodies, &c. he must go further, and attempt to assign the cause of gravity itself. But, how does he proceed in this matter? Not in the
the way of experiment, which had led him to his former discoveries, but in the way of conjecture, which will never lead any man to truth. He had recourse to a subtle elastic æther, not much different from that of the ancients, and by it accounted for every thing he did not know, such as the cause of gravitation, muscular motion, sensation, &c.
Notwithstanding the reputation of Sir Isaac, philosophers have generally looked upon this attempt as the foible of a great man, or, at least, as the most useless part of his works; and accordingly peruse it rather as a dream or a romance, than as having any connection with science. But we are sorry to find, that some late attempts have been made to revive this doctrine of æther, particularly in a dissertation De ortu animalium caloris, published in May last.
As the revival of an old doctrine becomes in some measure a new one, we shall plead no other apology for inserting a specimen of the method of reasoning employed in this dissertation.
The author makes frequent use of a species of argument termed dilemma by logicians. For example, in the first part of the work, after endeavouring to prove that animal heat cannot be owing to fermentation, the motion of the fluids, and other causes that have usually been assigned, he draws this conclusion:—
"If none of these causes are sufficient to produce the effect; therefore, by dilemma," says he, "it must be sought for in the nature and action of the nerves."
—This is a new species of dilemma:—If the author had proved, that the cause of heat in animals could not possibly exist any where, but either in fermentation, the motion of the fluids, &c. or in the nerves, after having disproved its existence in all the rest, his conclusion in favour of the nerves would have been just; but, as he has not so much as attempted this, the conclusion is not only false, but ridiculous.
However, upon the authority of this dilemma, the author first gives what he calls a Compend of a new doctrine concerning the nerves, and then proceeds to inquire in what manner the nerves produce animal heat: He tells us, "That thought (cogitatio) and sensation depend upon impulses either on the extremities of the nerves, or the sensorium commune, and the consequent motions produced by these impulses: That these motions are so quick, as to be almost instantaneous: That as all motion is mechanical; therefore thought, sensation, and muscular motion, must likewise be mechanical: That such quick motions cannot be produced without the intervention of some extremely elastic power; and, as Sir Isaac Newton has shown, that the impulses which occasion the different sensations must be owing to an elastic power; therefore the muscular motions of animals must be occasioned by the oscillations of some elastic power."
"But," says he, "as this elastic power cannot exist in the solid nervous fibres, nor in any inelastic fluid; therefore, by dilemma, it must exist in an elastic fluid; and hence also, by the former dilemma, this elastic fluid must be seated, either in the nerves, or in their medullary substance."
Here again the author calls Sir Isaac into his assistance.—"What confirms this opinion," says he, "is the Newtonian æther, which pervades all nature, and which, with a few variations in its modification, Sir Isaac has shown to be the cause of cohesion, elasticity, gravity, electricity, magnetism, &c. in the following manner: 1. As the rays of light, when reflected, do not touch the solid parts of bodies, but are reflected a little before they reach them, it is plain that the æther not only fills the pores of bodies, but likewise floats upon their surfaces; and hence it becomes the cause of attraction and repulsion.— 2. All metals, and inelastic fluids, are non-electrics; on the other hand, all solid bodies, metals excepted, are electrics, i. e. proper for accumulating æther. But æther, thus accumulated in such a variety of bodies, may produce various motions in the parts of these bodies, without inducing any change in the bodies themselves. Hence æther, with some variations in its modification, is sufficient to account for all the phenomena of electricity. 3. As iron, by accumulating æther around it, exhibits all the wonders of magnetism; so this magnetical æther is more analogous to the nervous æther of animals than any other kind of it. For, as the magnetical æther passes along iron without changing any part of the iron; so the nervous æther, in like manner, passes along the medullary substance of the nerves, and excites motion in any part that is continuous with them, without inducing any change in the nerves.— 4. The irritability and life of plants, which very much resemble those in animals, cannot be explained by any inelastic cause, and must therefore be attributed to an ætherial one. Lastly, As the common æther is differently modified in each of the substances above taken notice of, and also produces various motions or effects peculiar to each, it likewise varies and has some peculiar qualities when residing in animal bodies; so that the nervous or animal æther is not exactly the same, but differs in some respects from those species of æther which give rise to cohesion, gravity, magnetism, electricity, &c.
Having thus explained the nature and qualities of æther, our author starts a very important question, viz. "Whence is æther derived? and whether does it leave any body after having once got possession of it?" In answer to this, he observes, "That certain bodies have the power of collecting the electrical matter from every circumjacent body, and of accumulating it in their pores and on their surfaces, but do not suffer it again to transmigrate into any other body. There are other substances of an opposite nature, which do not accumulate the electric matter, but instantly allow it to pass into others, unless prohibited by an electric. Hence," says he, "nothing more is necessary for substances of the former kind, but to be in such circumstances as allow them to accumulate the electric matter. In the same manner," proceeds our author, "the nervous æther, which is diffused through every part of nature, flows
“ flows copiously into the medullary part of the nerves, “ when no obstacle stands in its way: but, when once “ it has got there, it keeps firm possession, and never “ afterwards leaves it. Now,” says he, “ a quan- “ tity of æther probably constitutes one of the stami- “ nal parts of animal bodies, and increases in propor- “ tion to their age and growth: For nothing is more “ ridiculous than to suppose that what is commonly “ called the nervous fluid can be daily wasted by la- “ bour and exercise, and daily repaired by a new se- “ cretion from the brain. To refute this vulgar no- “ tion, nothing more is necessary than to say, That “ it is one of Boerhaave's theories, and must be false, “ as all Boerhaave's other theories have been proved “ to be ill-founded! But æther is of a more fixed “ and determinate nature; whenever it gets possession “ of any substance, it never forsakes it, unless the “ texture and constitution of the body itself be chan- “ ged. Hence,” continues our author, “ the æther “ of an acid body remains as long as the body con- “ tinues to be acid; the same observation holds with “ regard to the æther of an alkaline body: But, if “ these two be blended together into a neutral salt, “ the æther must likewise be changed into a neutral; “ and therefore, in the formation of the medullary “ or staminal part of animals, the æther which before “ belonged to, or had the properties of some other sub- “ stance, is instantaneously changed into animal æther, “ and remains so till the dissolution of that animal.”
Our author next observes, “ That bodies require to “ be in a certain state or condition in order to the for- “ mation of an æther that is proper for them. This “ condition of bodies is called an excited state: Thus, “ as sulphur, when fluid, does not receive the electric “ matter, but, when solid, instantly receives it; in “ the same manner, the nerves, though properly “ formed, do not admit an æther adapted to their “ nature, unless they be in an excited state. Hence,” says he, “ the æther of a dead, and that of a living “ person, are very different, although the texture and “ figure of the nerves be the same. The state neces- “ sary for constituting the æther of a living animal, “ seems to depend on heat and moisture; because these “ things are absolutely necessary in the constitution of “ life: And hence,” concludes our author, “ the ex- “ cited state of the nerves depends on heat and moi- “ sture. There are also certain circumstances,” says he, “ which contribute to render the state of the “ nerves more or less apt for accumulating æther: A “ spasmodic fever, for example, renders the nerves of “ the whole body less pervious to the motion of the “ æther; and hence, in cases of this nature, health, “ and all the vital functions, must be injured.”
“ These,” our author observes, “ are the outlines “ of a new doctrine concerning the nature and func- “ tions of the nerves;” and, upon this foundation, “ proceeds to give his new theory of animal heat.
“ From the foregoing reasoning,” says he, “ the “ heat, as well as all the functions of animals, seem “ to be occasioned by the oscillations of the nervous “ æther betwixt the extremities of the sentient nerves
“ and the brain, or, more properly, betwixt the brain “ and muscles. But electrical æther, as above ob- “ served, varies a little from common æther; all in- “ elastic fluids, as was likewise formerly remarked, “ are non-electrics; and all solid bodies, metals ex- “ cepted, are electrics: These circumstances,” says our author, “ seem to be owing to the oscillations of “ the electric matter in bodies. In the same manner,” says he, “ the nature of animals may be such, and the “ nerves may be so constituted, as to form an æther ad- “ apted to their nature, and to excite those oscillations “ which occasion animal heat. The wonderful effects “ of heat and cold upon the nerves,” continues our author, “ confirms this theory: Every action, and “ even life itself, requires a certain degree of heat; “ for, as the heat of the external air is so variable, it “ was absolutely necessary that animal bodies should “ be endowed with the faculty of producing a degree “ of heat suited to their nature, independent of ex- “ ternal circumstances: Hence we see the reason why “ the degree of heat so seldom varies in the same spe- “ cies of animals. However, although the nervous “ æther is always ready for exciting heat by its oscil- “ lations; yet, in order to bring about this effect suc- “ cessfully, external stimuli are necessary, otherwise “ the æther would be in danger of stagnating, which “ would occasion sleep, a palsy, and, last of all, death. “ The most permanent of these stimuli is the pulsa- “ tion of the arteries; which is the reason why heat “ is so connected with the circulation of the blood, “ and why many authors have mistaken it for the true “ cause of animal heat.”
Our author now concludes with observing, “ That “ by his theory, the varieties of heat in different parts “ of the body, the heat and flushing of the face from “ shame, and all the other phenomena of heat in ani- “ mal bodies, admit of a better explanation, than by “ any other theory hitherto invented.”
Having thus given a pretty full account of an at- “ tempt to explain the most abstruse operations of na- “ ture, as nearly as possible in the very words of the “ author, we cannot deny ourselves the liberty of mak- “ ing a few observations.
To give a formal refutation of this author's reason- “ ing, is no part of our plan. It is, perhaps, wrong “ to say that he has reasoned; for the whole hypothet- “ ical part of his essay is a mere farrago of vague asser- “ tions, non-entities, illogical conclusions, and extra- “ vagant fancies. His æther seems to be an exceedingly “ tractable sort of substance: Whenever the qualities of “ one body differ from those of another, a different modi- “ fication of æther at once solves the phenomenon. The æther of iron must not, to be sure, be exactly “ the same with the nervous æther, otherwise it would “ be in danger of producing sensation in place of mag- “ netism. It would likewise have been very improper “ to give the vegetable æther exactly the same quali- “ ties with those of animal æther; for, in such a case, “ men would run great risk of striking root in the soil, “ and trees and hedges might eradicate and run about “ the fields. Nothing can be more ludicrous than to fe-
a writer treating a mere ens rationis as familiarly as if it were an object of our senses: The notion of compounding the æther of an acid and that of an alkali, in order to make a neutral of it, is completely ridiculous. But if men take the liberty of substituting names in place of facts and experiments, it is an easy matter to account for any thing.
By this method of philosophising, obscurity is for ever banished from the works of nature. It is impossible to gravel an ætherial philosopher. Ask him what questions you please, his answer is ready:—"As we cannot find the cause anywhere else; ergo, by this lemma, it must be owing to æther!" For example, ask one of those sages, What is the cause of gravity? he will answer, "Tis æther! Ask him the cause of thought, he will gravely reply, "The solution of this question was once universally allowed to exceed the limits of human genius: But now, by the grand discoveries we have lately made, it is as plain as that three and two make five:—Thought is a mere mechanical thing, an evident effect of certain motions in the brain produced by the oscillations of a subtle elastic fluid called æther!" This is indeed astonishing!
Such jargon, however, affords an excellent lesson to the true philosopher. It shows to what folly and extravagance mankind are led, whenever they deviate from experiment and observation in their inquiries into nature. No sooner do we leave these only faithful guides to science, than we instantly land in a labyrinth of nonsense and obscurity, the natural punishment of folly and presumption.
When endeavouring to account for that propensity in the human mind which prompts us to attempt the solution of things evidently beyond our reach, we recollected a passage in Swift's works, which explains it in the most satisfactory manner.
"Let us next examine (says the Dean) the great introducers of new schemes in philosophy, and search till we can find from what faculty of the soul the disposition arises in mortal man, of taking it into his head to advance new systems, with such an eager zeal, in things agreed on all hands impossible to be known; from what seeds this disposition springs, and to what quality of human nature these grand innovators have been indebted for their number of disciples; because it is plain, that several of the chief among them, both ancient and modern, were usually mistaken by their adversaries, and indeed by all except their own followers, to have been persons crazed, or out of their wits; having generally proceeded, in the common course of their words and actions, by a method very different from the vulgar dictates of unrefined reason; agreeing, for the most part, in their several models, with their present undoubted successors in the Academy of modern Bedlam. Of this kind were Epicurus, Diogenes, Apollonius, Lucretius, Paracelsus, Des Cartes, and others; who, if they were now in the world, tied fast, and separated from their followers, would, in this undistinguishing age,
incur manifest danger of phlebotomy, and whips, and chains, and dark chambers, and straw. For what man, in the natural state or course of thinking, did ever conceive it in his power to reduce the notions of all mankind exactly to the same length, and breadth, and height of his own? Yet this is the first humble and civil design of all innovators in the empire of reason.—Now, I would gladly be informed, how it is possible to account for such imaginations as these in particular men, without recourse to my phenomenon of vapours, (i. e. æther), ascending from the lower faculties to overshadow the brain, and there distilling into conceptions, for which the narrowness of our mother-tongue has not yet assigned any other name besides that of w madness or phrenzy. Let us therefore now conjecture how it comes to pass that none of these great projectors do ever fail providing themselves and their notions with a number of implicit disciples; and I think the reason is easy to be assigned.—For there is a peculiar string in the harmony of human understanding, which, in several individuals, is exactly of the same tuning. This if you can dextrously screw up to its right key, and then strike gently upon it, whenever you have the good fortune to light among those of the same pitch, they will, by a secret necessary sympathy, strike exactly at the same time. And in this one circumstance lies all the skill or luck of the matter: For if you chance to jar the string, among those who are either above or below your own height, instead of subscribing to your doctrine, they will tie you fast, call you mad, and feed you with bread and water. It is therefore a point of the nicest conduct, to distinguish and adapt this noble talent with respect to the difference of persons and of times.—For, to speak a bold truth, it is a fatal miscarriage so ill to order affairs as to pass for a fool in one company, when in another you might be treated as a philosopher: Which I desire some certain gentlemen of my acquaintance to lay up in their hearts as a very seasonable innuendo."
We would not have dwelt so long upon this article, had it not been to guard, as far as our influence extends, the minds of those who may be unacquainted with the genuine principles of philosophy, from being led into a wrong track of investigation.