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previously, or the needles placed equally in advance, these nearly received the same degree of magnetism. Still there is in this case a sudden change in the electric movement, at the instant the plates are withdrawn from the liquid.
If we leave the plates of an apparatus a long time immersed, the difference of the magnetism of the two needles, the one without metallic envelope, the other enveloped, becomes greater and greater in proportion as the action is less active ; doubtless because the influence of the small spark, though it does become enfeebled, diminishes relatively less than that of the continuous current. Thus three pairs of needles, with and without metallic envelopes, having been magnetized, the one at the commencement of the immersion of the pile, the second 8' after, the third at the end of 20', the differences of the times employed by the two needles of the same pair to make sixty oscillations were 15", 48”, and 2'; the time employed by the needle without envelope being 2', 52" ; 2', 55"; and 3', 37". In the state of saturation the duration of sixty oscillations is 2', 38".
The redeeming influence of the metallic envelopes increases a little with their thickness. I ought to search out, if in the case where a thick envelope enfeebles the magnetism, a thin envelope would augment it. The envelopes tried were perhaps too thin, their influence being insensible. The small difference of action of the two envelopes of unequal thickness is without doubt, the part of the effect due to the continuous current.
I am far from well recognizing the circumstances in which are produced, under the influence of voltaic currents, the actions I have just been speaking of. I have sometimes found that the thick metallic envelopes augmented the magnetism in a superior quantity to a quarter of these experiments. When that happened the needles were withdrawn from the helices, without at all changing the immersions of the plates or the communications. The conducting wire was soldered to the extreme elements, and each plate of zinc soldered to the plate of copper following. In truth there is here a circumstance which the discoveries M. Arago will not permit me to neglect: the displacement of the needles in relation to the wire conductor and to the copper cylinder.
Two needles enclosed, the one in a copper tube, the other in one of wood, and similarly placed between two magnets sufficiently feeble only to give a degree of magnetism far removed from the state of saturation, have always received degrees of magnetism sensibly equal. We ought in all cases to take care to provide against the effect due to the inclination of their magnetic axis.
I have been obliged to expose new facts independently of any explanation ; I may now, however, be permitted to point out rapidly the consequences.
An electric discharge is a phenomenon of movement. This movement, is it a continuous transport of matter in a determined direction? Then the alternative opposed magnetisms which we observe at different distances from a rectilinear conductor, or in a helix with gradually increasing discharges, would be due uniquely to mutual reactions of magnetic particles in the steel needles. The manner in which the action of a wire changes with its length appears to me to exclude this supposition.
The electric movement during the discharge, is it composed, on the contrary, of a series of oscillations transmitted from the wire* to the surrounding media, and soon recovered by the resistances which rapidly are borne away with the absolute quickness of the agitated particles ?
All the phenomenà conduce to this hypothesis, which makes to depend, not only the intensity but the direction of the magnetism, on laws following which the small movements were weakened in the wire, in the medium which surrounds it, and in the substance which receives the magnetism.
The oscillations in the wire will have quickness absolutely as much less as they spread themselves more and more rapidly as this wire is increased in length, thinner, and as the resistance proper to its nature becomes more considerable. We thus explain how it is that, with a rectilinear conductor and a given discharge, a length of wire which produces the strongest magnetism, if the length is less, the small movements diminish too slowly; if greater, their intensity is too much enfeebled.
Inasmuch as powerful metallic substances, as we have seen, sometimes increase and sometimes enfeeble the magnetism, it is sufficient that they weaken, in the two cases, the small movements propagated by the wire, and that their section be not simply proportional to the absolute quickness of these movements. It suffices then to admit, with these infinitely small displacements, what the discovery of M. Arago puts in evidence with oscillations of a limited amplitude.
Under the influence of the pile, the relative phenomena, whether of direct magnetism or of the action of metallic envelopes, are analogous to those presented by the discharges of ordinary electricity. When we destroy the communication whilst the needles are submitted to the action of a wire conductor, it is natural to think that the equilibrium is re-established in this wire by a series of small movements analogous to those excited by the discharge. But when the needles are taken away from the voltaic action, without there being a sudden interruption of the circuit, the influence which a metallic envelope several times exercised to augment the magnetism, seemed to indicate in the closed circuit the existence of two contrary currents, animated by very different speeds, or rather by small movements, the duration and quickness of which were in the two opposite direc
The wire, which may be entirely insulated from the ground and from the battery, receives and transmits the discharge by two sparks without the mag. netic effects already described taking place.
tions. A pendulum oscillating in the medium, whose density decreases continually from one extremity to the other of the axis it travels over, will be an example of this kind of movement. Does not the contact of the two metals present such a medium ? This hypothesis, which may give birth to some researches, proper either to confirm or destroy it, can only acquire additional weight by new facts.
In applying to the experiments contained in this memoir the considerations which I limit myself only to indicate here, I have not found anything for which they do not easily render a reason. But it would be too long, and perhaps misplaced, to enter on the subject in a first work in this theoretical discussion. New researches, which it has suggested to me, will, I hope, furnish me with an occasion of returning to it and the means of developing it.
On the Chemical Statics of Organized Beings. Extract from the
concluding Lecture, in L'Ecole de Médicine in Paris. By M. DUMAS.
Life, whose painful mysteries you are called upon to fathom, exhibits among its phenomena some which are manifestly connected with the forces that inanimate nature herself brings into action, others which emanate from a more elevated source, less within the reach of our boldest stretch of thought.
I. Plants, animals, man, contain matter. Whence comes it? What does it effect in their tissues and in the fluids which bathe them? What becomes of it when death breaks the bonds by which its different parts were so closely united ?
These are the questions which we touched upon together, at first with hesitation, for the problem might be far above the powers of modern chemistry; we afterwards considered them with somewhat more confidence, as we felt from the silent and inward assent of our understandings that the path was sure, and that we could descry the goal gradually standing out, clear of all that obstructed our vision. If from these labours which you have witnessed, or, I should rather say, in which you have taken part; if from this scientific effort there have arisen some general views, some simple formulæ, it is my duty to become their historian ; but allow me the pleasure of adding, that they belong to you, that they belong to our school, the intelligence of which has been exercised on this new ground. It is the ardour with which you have followed me in this career that has given me strength to pursue it ; it is your interest which has sustained me; your curiosity which has awakened mine : your confidence which has made me see, and which proves to me at this moment that we are still in the path of truth.
These remarks will remind you of the wonder with which we found that, of the numerous elements of modern chemistry, organic nature borrows but a very small number ; that from these vegetable or animal matters, now multiplied to infinity, general physiology borrows not more than from ten or twelve species ; and that all the phenomena of life so complicated in appearance, belong, essentially, to a general formulæ so simple, that, so to speak, in a few words the whole is stated, the whole summed up, the whole foreseen.
Have we not proved in fact, by a multitude of results, that animals constitute, in a chemical point of view, a real apparatus for combustion, by means of which, burnt carbon incessantly returns to the atmosphere under the form of carbonic acid ; in which hydrogen burnt without ceasing, on its part continually engenders water; whence in fine, free azote is incessantly exhaled by respiration, and azote in the state of oxide of ammonium, by the urine?
Thus from the animal kingdom, considered collectively, constantly escape carbonic acid, water in the state of vapour, azote, and oxide of ammonium : simple substances, and few in number; the formation of which is strictly connected with the history of the air itself. Have we not, on the other hand, proved that plants, in their normal life, decompose carbonic acid for the purpose of fixing its carbon and disengaging its oxygen ; that they decompose water to combine with its hydrogen, and to disengage, also, its oxygen; that in fine, they sometimes borrow azote directly from the air, and sometimes indirectly from the oxide of ammonium, or from nitric acid ; thus working in every case, in a manner the inverse of that which is peculiar to animals? If the animal kingdom constitutes an immense apparatus for combustion, the vegetable kingdom, in its turn constitutes an immense apparatus for reduction, in which re. duced carbonic acid yields its carbon, reduced water its hydrogen, and in which, also, reduced oxide of ammonium and nitric acid yield their ammonium, or their azote.
If animals, then, continually produce carbonic acid, water, azote, oxide of ammonium ; plants incessantly consume oxide of ammonium, azote, water, carbonic acid. What the one class of beings gives to the air, the other takes back from it ; so that to take these facts at the loftiest point of view of terrestrial physics, we must say that, as to their truly organic elements, plants and animals spring from air, are nothing but condensed air; and that in order to form a just and true idea of the constitution of the atmosphere at the epochs which preceeded the birth of the first organized beings on the surface of the globe, there must be placed to the account of the air, by calculation, that carbonic acid and azote whose elements have been appropriated by plants and animals. Thus plants and animals come from the air, and thus to it they return; they are real dependencies of the atmosphere.
Plants, then, incessantly take from the air what is given to it by animals ; that is to say, carbon, hydrogen, and azote, or rather, carbonic acid, water, and ammonia.
It now remains to be stated, how in their turn, animals acquire those elements which they restore to the atmosphere ; and we can
not see without admiring the sublime simplicity of all these laws of nature, that animals always borrow these elements from plants themselves.
We have, indeed, ascertained, from the most satisfactory results, that animals do not create true organic matters, but that they destroy them; that plants on the contrary, habitually create these same matters, and that they destroy but few of them; and that in order to effectuate particular and determinate conditions.
Thus it is in the vegetable kingdom that the great laboratory of organic life resides; there it is that the vegetable and animal matters are formed, and they are there produced at the cost of the air.
From vegetables these matters pass ready-formed into the herbivorous animals, which destroy a portion of them, and accumulate the remainder in their tissues.
From herbiverous animals, they pass ready formed into the carniverous animals, who destroy or retain some of them, according to their wants.
Lastly, during the life of these animals, or after their death, these organic matters, as they are destroyed, return to the atmosphere whence they proceeded.
Thus closes this mysterious circle of organic life at the surface of the globe. The air contains, or engenders, oxidized products, as carbonic acid, water, nitric acid, oxide of ammonium. Plants, constituting true reducing apparatus, possess themselves of their radicals, carbon, hydrogen, azote, ammonium. With these radicals they form all the organic, or organizable matters, which they yield to animals. These, forming in their turn, true apparatus for combustion, re-produce carbonic acid, water, oxide of ammonium, and nitric acid, which return to the air, to produce anew, and through endless ages the same phenomena.
And if we add to this picture, already, from its simplicity and its grandeur so striking, the indisputable function of the solar light, which alone has the power of putting in motion this immense apparatus, this apparatus never yet imitated, constituted of the vegetable kingdom, and in which is accomplished the reduction of the oxidized products of air, we shall be struck with the import of these words of Lavoiser :
• Organization, sensation, spontaneous movement, life, exist only at the surface of the earth, and in places exposed to the light. It would seem that the fable of the torch of Prometheus was the expression of a philosophic truth which had not escaped the ancients. Without light, nature was without life, was dead and inanimate : by the gift of light, a beneficient God spread upon the surface of the earth organization, feeling, and thought."
These words are as true as they are beautiful. If feeling and thought, if the noblest faculties of the soul and of the intellect, have need for their manifestation of a material covering, to plants is assigned the framing of its web with the elements which they borrow