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flame has thus been rendered visible, the revolution of the eye-piece, to the right or left, more or less, will cause its extinction; and the further motion of the eye-piece to the one side or other of this position will produce the re-appearance of the light, and that with complementary tints, according as this further motion is to the right or left hand. The direction in which the rotation takes place will, of course, be reversed by reversing either the course of the ray, or the poles of the magnet. Hence it follows, that the polarized ray is made to rotate in the same direction as the currents of positive electricity are circulating, both in the helices composing the electro-magnet, and also as the hypothetical currents, which according to Ampere's theory, circulate in the substance of a steel magnet. The laws of this action may perhaps be best enunciated in the language of the author :

property, though in a less degree than the heavy glass first tried. Rock-salt and fluorspar give evidence of the power in a slight degree; Iceland-spar, sulphate of baryta, sulphate of lime, and carbonate of soda, appear to be without action on light. Almost if not all liquids, certainly all liquids tried by Dr. Faraday, showed the effect. When these bodies possess a rotative power of their own, as is the case with oil of turpentine, sugar, tartaric acid, tartrates, &c., the effect of the magnetic force is to add to or subtract from their specific force, according as the natural rotation, and that induced by the magnetism, is right or left-handed. With regard to air and gaseous bodies, Dr. Faraday has as yet been unable to detect the exercise of this power in any one of the substances in this class. A vast number of gases as well as air were submitted to experiment, but they all gave negative results.

From the relation which we have pre"Magnetic lines then, in passing through viously shown exists between the two forces, silicated borate of lead, and a great number of magnetism and electricity, the probability other substances, cause these bodies to act that an electric current would give the upon a polarized ray of light, when the lines are parallel to the ray, or in proportion as they same result of action on light, as a magnet, are parallel to it; if they be perpendicular to must be apparent to the most casual reader. the ray, they have no action upon it. They This was tried by the discoverer with sucgive the diamagnetic the power of rotating the cess; a quantity of covered copper wire, ray; and the law of this action on light is, that wound in the form of a helix, supplied a if a magnetic line of force be going from a form of apparatus, in which great lengths north pole, or coming from a south pole, along of diamagnetics, such, for example, as wathe path of a polarized ray, coming to the obter in a long glass tube, and especially of server, it will rotate that ray to the right hand; or, that if such a line of force be coming from such bodies as appeared to be but little af a north pole, or going from a south pole, it will fected between the poles of the magnet, rotate such a ray to the left hand."

could be submitted to examination, and their effect exalted. The electric current We cannot, within our limits, follow Dr. passed through the helix was in all the exFaraday through all the well-contrived and periments derived from a battery of ten lucidly described experiments by which the pairs of Grove's plates. A tube within the inquiry was pursued. We must content helix being filled with distilled water was ourselves with enunciating the different cir-placed in the line of the polarized ray, so cumstances which affect, limit, and define that by examination through the eye-piece, the extent and nature of this new power of action on light. In the first place, the rotation appears to be in proportion to the extent of the diamagnetic through which the ray and magnetic lines pass. The power of rotating the ray of light increases with the intensity of the magnetic lines of force. Other bodies, besides the heavy glass, possess the same powers of becoming, under the influence of magnetic force, active on light; though, if all transparent bodies possess the power of exhibiting the action, they have it in very different degrees; and up to this time there are some that have not shown it at all; glass made of the borate of lead, flint-glass, crown-glass, all exhibit the

the image of the lamp-flame produced by the ray could be seen through it. The eyepiece being turned so that the image of the flame could no longer be seen through it, and the battery being connected with the helix, the image of the flame instantly reappeared, and continued as long as the electric current was passing through it; on stopping the current, the image disappeared. The light does not rise up gradually, as in the case of electro-magnets, but instantly. In this experiment it cannot be doubted that a ray of light is electrified, and the magnetic resultant of the electric forces illuminated.

The law of this action of electricity is as

simple and beautiful as that we have already | stance, rendered visible by the light, and this described in reference to the effect of the was what I meant by illumination." magnet-and for its description we will again quote from the Researches :

But, although the experiments and expressions of Faraday have not established, "When the current was sent round the helix or been intended by the author to establish in one direction, the rotation induced upon the the fact, that the lines of magnetic force ray of light was one way; and when the curare luminous, yet this assertion has been rent was changed to the contrary direction, the rotation was the other way. In order to express the direction, I will assume, as is usually done, that the current passes through the acid to the platinum in the same cell: if such a current pass under the ray towards the right, upwards on its right side, and over the ray towards the left, it will give the left-handed rotation to it; or if the current pass over the ray to the right, down on the right side and under it towards the left, it will induce it to rotate to the right hand. The law, therefore, by which an electric current acts on a ray of light is easily expressed. When an electric current passes round a ray of polarized light in a plane perpendicular to the ray, it causes the ray to revolve on its axis as long as it is under the influence of the current, in the same direction as that in which the current is passing."

All bodies are affected by helices as by magnets, and according to laws which show that the causes of the action are identical as well as the effects. And although hitherto the magnetic and electric forces appear to exert no power on the ordinary or depolarized ray of light, we can hardly doubt but that they have some special influence, which probably will soon be made apparent by experiment; neither can it be supposed

otherwise than that the same kind of action

should take place on the other forms of radiant agents, as heat and chemical force.

magnetic force."

A few words are necessary ere we quit this part of the subject, relative to the title of the paper under consideration, or rather to the latter portion of it-we mean the expression, "Illumination of lines of the Many persons anticipated, and it has even been boldly asserted, that they have been rendered luminous. Such a meaning was never intended by the author; and in an explanatory note, appended to the paper, he says that :

boldly made by Barón Reichenbach, in the
"Researches on Magnetism" before us.
We are aware that we are treading on dan-
gerous ground; we are approaching the
confines of the oft-debated and much ridi-
culed science of animal magnetism. The
facts detailed in his volume are startling,
and will probably be received in England
with incredulity; but it must also be re-
membered, that the name of Reichenbach
is familiar to chemists for many laborious
researches and important discoveries; and
his character as an experimentalist has
always stood particularly high for minute
accuracy and untiring perseverance. These
researches, moreover, were published in a
journal standing in the highest rank among
Chemie und Pharmacie.'
chemical periodicals, the 'Annalen die
We are, of

course, far from vouching for the truth of
the facts; our object is simply to make
the experiments may be repeated and tested
them generally known, under the hope that
by those to whom the opportunity may pre-
the volume, justly remarks, that "in mat-
sent itself. Dr. Gregory, the translator of
the only question is this, 'It it true?' and
ters of observation, especially when new,
We cannot say what is possible, and no
not 'Is it possible?' or 'Is it absurd?'

facts can be absurd."

Reichenbach, then, asserts that from nuat the poles and sides of powerful magnets merous experiments he has discovered, that there is an appearance of light, visible only to the sensitive. The following quotation from the work will explain what he means by the sensitive ::

"Diseased sensitive subjects experience different sensations (when a magnet is drawn down the body), often disagreeable, and occasionally giving rise to fainting, to attacks of "He intended to express that the line of catalepsy, or to spasms so violent that they magnetic force was illuminated, as the earth might possibly endanger life. In such cases, is illuminated by the sun, or the spider's web which generally include somnambulists, there illuminated by the astromomer's lamp. Em- occurs an acuteness of the senses: smell and ploying a ray of light, we can tell, by the eye, taste, for example, become astonishingly delithe direction of the magnetic lines through a cate and acute; many kinds of food become body; and by the alteration of the ray, and its intolerable, and the perfumes, most agreeable optical effect on the eye, can see the course of at other times, become offensive. The patients the lines just as we can see the course of a hear and understand what is spoken three or thread of glass, or any other transparent sub-four rooms off, and their vision is often so irri

table, that, on the one hand, they cannot endure the sun's light or that of a fire; while, on the other, they are able in a dark room to distinguish not only the outlines, but also the colors of objects, where healthy people cannot distinguish any thing at all. Up to this point, however strange the phenomena, there is nothing which cannot easily be conceived, since animals and men differ very much in the acuteness of the senses, as is daily experienced."

a lens, and the inverted image accurately described, and its position pointed out by the sensitive patients.

The question naturally arises, how is it that the magnetic light and flame are ordinarily invisible. It is thus answered by the author :

"That it is invisible to ordinary eyes is not wonderful, when we reflect that the sun's light, ing to Leslie, even 12,000 times as poweriul as according to Wollaston, is 5,560 times, accordthe light of a candle; that many flames, as those of alcohol or pure hydrogen, are invisi ble not only in the sun's light, but in strong daylight. From these latter to entire invisibility to ordinary eyes, even in the dark, is a

It was with six such sensitive patients that the experiments were made: to one and all of them, there appeared in the dark, a luminosity like a moving flame at the poles and around powerful magnets: the vividness of the luminosity varied in all the cases, according to the degree of sensitive-step easily conceived." ness and the diseased state of the body. It has been a well-known scientific fact, This phenomenon was only apparent when that the magnetic needle suffers a very great the armature of the magnet was removed, disturbance both before and on the appearand ceased when it was replaced. A bar, ance of the aurora borealis; and on some horse-shoe, and electro-magnet all presented occasions even a deviation of 8° has been the same appearances; in the last, however, observed. Arago has noticed that at Paris, it was the most distinct, in the first it was the needle was affected by auroræ that most faint. The phenomenon in all these were seen in Scotland; and so striking is cases presented the appearance of a flame, the connexion between the two classes of with a play of colors shooting out rays as facts, that the existence of the aurora could large as the magnet, and a general weaker be inferred from the derangements of the light over the whole surface, at the junction needle. The real nature of the aurora has of the plates of which the magnet itself was never been clearly determined, although it composed. To test still further the pheno- is generally conceived to be dependent on menon, recourse was had to the following electricity. Reichenbach, however, conexperiment. A very sensitive daguerreo-ceives, from the result of the experiments type plate was placed opposite to a magnet we have narrated, that they are visible in a closed box, surrounded with thick bedmagnetic lights. clothes, so that no ordinary light could enAfter sixty-four hours' exposure, the "The similarity of the light," he observes, plate, when held over mercurial vapor," as seen by Mademoiselle Reichel (one of his was found fully affected, as by light, over the whole surface. To this experiment, however, there are, to our minds, two strong objections. The first of these is, that heat, electricity, galvanism, produce impressions analogous to those of the sun's rays, and, therefore, the effect of magnetism on the prepared plate may be entirely independent of this pretended luminosity. Again, the color of the luminous flame of magnets is described as red. Now it is well known by all who have practised the photographic art, that the red rays of the spectrum are inert on chemical compounds, the rays at the opposite end of the spectrum being the only agents in the production of daguerreotype effects. This fact appears to us most strongly to militate against this experiment as a proof of the luminosity. Another experiment is stated to have been made, in which the magnetic light was condensed by

ter.

sensitive patients), to the aurora is striking, and it must be borne in mind that the aurora, affects the needle very strongly; just as the or the magnetism of the earth producing it, magnet used by the author and giving out light, visible to sensitive persons, did also."

He is far from considering their identity as proved, because between light which is visible to healthy eyes and that which is invisible there is a gap not easily filled up. But at least the analogy is so great, that their identity acquires a high degree of probability.

We now turn to the consideration of the second part of the researches of Faraday, contained in the 20th and 21st series of the Experimental Researches in Electricity,' under the title of New Magnetic Actions and the Magnetic Condition of Matter.' The phenomena which we shall now have to describe are altogether different in their

nature from those we have previously [netic force which the body when reduced be

neath it could acquire. In this view, iron and nickel were not considered as exceptions from the metals generally with regard to magnetered as an exception from this class of bodies ism, any more than mercury could be considas to liquefaction."

noticed; they prove not only a magnetic condition of the substances referred to, unknown, and even unsuspected before, but also many others, including a vast number of opaque and metallic bodies, and perhaps all except the magnetic metals and their compounds. And they also present us In consequence of this opinion, he made with the means of undertaking the corre-experiments on the point. The metals tried Jation of magnetic phenomena, and perhaps were arsenic, antimony, bismuth, cadmium, the construction of a theory of general cobalt, chromium, copper, gold, lead, mermagnetic action founded on simple funda-cury, palladium, platinum, silver, tin, zinc, mental principles. as also plumbago; they were all exceed

We have already said that since the ingly reduced in temperature, but in none period of Coulomb's experiments previ- of these cases could he obtain the least inously referred to, a general impression has dication of magnetism. His present reprevailed amongst philosophers that all sub-searches have now revealed to us the cause stances were acted on by magnets, in the of failure.

served that a needle of wood, under certain conditions, pointed across the magnetic curves ; and it is also mentioned by Becquerel, that a needle of wood placed itself parallel to the wires of a galvanometer. These effects, however, were referred by the latter philosopher to a degree of magnetism less than that of the tritoxide of iron, but the same in character, for he makes the following remarks:

same manner as iron, nickel, &c., though But though this opinion was so prevathis influence was very different in degree.lent, facts were not wanting to cast over it Coulomb's experiments were carried on in a shade of doubt; Coulomb himself ob1802, and in that year he announced as an incontrovertible fact, that all substances whatever, when formed into small needles, turned themselves in the direction of the poles of the magnets, and after a few oscillations, finally settled in that position. Gold, silver, brass, wood, and all other substances, whether organic or inorganic, according to him, in this way obeyed the power of magnets. In the present state of our knowledge, we can only explain the experiments, by supposing that all the bodies. which he tried, and which he deemed susceptible of magnetism, were impure, and contained, either minute quantities of iron, or other magnetic metals, which gave them their susceptibility. So universal was the reliance placed upon these experiments of Coulomb, that even the author whose recent discoveries have disproved this long prevailing belief entertained the same opinion.

In the London and Edinburgh Philosophical Magazine, for March, 1836, the following remarkable passage is from a paper by Dr. Faraday :

a

"This difference of effect, which established line of demarcation between these two species of phenomena, is due to this, that the magnetism being very feeble in the tritoxide of iron, wood, &c., we may neglect the reaction of the body on itself, and therefore the direct action of the bar ought to overrule it."

In 1829, M. le Bailiff, of Paris, showed that both bismuth and antimony repelled the magnetic needle, and even long before this, in the year 1778, the repulsion of bismuth by a magnet was observed by Brugmans. It is an astonishing fact that this experiment should have so long remained unnoticed, and without results. It is evident that it must have been considered as a peculiar and isolated fact, and not the consequence of a general property which is now shown to belong to all matter.

"General views have long since led me to an opinion, which is probably also entertained by others, that all the metals are magnetic in the same manner as iron, though not at common temperatures, or under ordinary circumstances. I do not refer to a feeble magnetism, uncertain in its existence and source, but to a distinct and decided power, such as that possessed by iron and nickel; and my impression has been that there was a certain temperature for each body beneath which it was magnetic, but above which it lost that power; and fur-netic force, as universally as it is to the ther, that there was some relation between this gravitating, the electric, the cohesive, and point of temperature and the intensity of mag-the chemical forces; but this influence is

With these preliminary remarks, which, however, were necessary for the appreciation of the novelty and merit of the present discovery, we proceed at once to its enunciation. All matter is subject to the mag

"Having arrived at this point," observes Mr. Faraday, "I may observe that we can now have no difficulty in admitting that the of a magnetic property in matter, new to our phenomena abundantly establish the existence knowledge. Not the least interesting of the consequences that flow from it is the manner in which it disposes of the assertion that all bodies are magnetic. Those who hold this view mean, that all bodies are magnetic as iron is, and say that they point between the poles. The new facts give not a mere negative to this statement, but something beyond, namely, an affirmative as to the existence of forces in all ordinary bodies directly the opposite of those existing in magnetic bodies, for whereas those practically produce attraction, these produce repulsion; those set a body in an equatorial position: and the facts, with rethe axial direction, but these make it take up gard to bodies generally, are exactly the reverse of those which the view quoted indicates."

not in all cases, as was formerly believed, mutton, beef, blood, leather, apple, bread,of the same character as that exerted upon nay, if a man could be suspended with iron; on the contrary, different bodies are sufficient delicacy and placed in the magacted upon by the magnetic forces in two netic field, he would be repelled and point different and opposite ways; and they may equatorially; for all substances of which he accordingly be conveniently divided into is composed, including the blood, possess two classes. The first class is that of this property. which iron is the type; the bodies belonging to it, which are somewhat limited, are called MAGNETICS; when suspended between the poles of an electro-magnet so as to swing freely, they are attracted by the pole to which they may happen to be nearest, and if allowed to oscillate, they will ultimately take up a position coincident with the direction of the magnetic forces, or in other words, in a straight line between the poles of the magnet; this direction the author calls the axial position. To this class belong all those metals which have hitherto been termed the magnetic metals, as iron, nickel, cobalt, as well as many other bodies hitherto regarded as unmagnetic, as for example, peroxide of iron, paper, sealing-wax, China ink, Berlin porcelain, plumbago, tourmaline, charcoal, &c. In addition to the metals already known to be magnetic, the following have by these experiments been also proved to be so; titanium, manganese, cerium, chromi- There are some other circumstances in um, platinum, palladium. The second reference to these two actions of magnets great class of bodies are found, in direct on all substances which are extremely inopposition to the former, to arrange them-teresting, and consequently must not be. selves in right angles to the magnetic passed over in silence. To whichever class poles, and consequently to the magnetic a substance belongs, its compounds and lines of force, a position in which they re- salts also belong. Thus iron is magnetic; main, as long as the power of the magnet is so are its salts and native compounds. kept up. This position the author calls the Green bottle-glass and crown-glass are both equatorial direction. All these bodies, too, magnetic, from the iron they contain. Flintare repelled from either pole of the mag-glass and the heavy glass already named net, the law in this respect being, that all are diamagnetic, for they contain no iron, such substances are repelled from the Bismuth is diamagnetic; its salts and comstronger to the weaker points of action. pounds are likewise so. But we may adTo this class the title of DIAMAGNETICS is vance a little further: not only are the salts given, and of it bismuth may be considered of substances acted on in the same way as the type. The bodies belonging to it are their base, but the solutions of these salts exceedingly numerous: of the metals the even obey the same mysterious power. A following have been found to be diamag- tube, for example, filled with a clear solunetic: lead, bismuth, arsenic, iridium, urani- tion of proto or persulphate of iron, is um, tungsten, silver, antimony, sodium, attracted by the poles, and points well in an magnesium, calcium, strontium, barium, axial direction. The magnetic properties potassium, gold, copper, cadmium, mer- of compound bodies depend on those of cury, tin, zinc. To this class also belong substances so widely differing in properties as those contained in the following list. Glass, crystalline bodies, whether belong ing to the single or double refracting class, phosphorus, sulphur, water, alcohol, ether, oils, caoutchouc, sugar, starch, wood, ivory, VOL. IX. No. I.

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their elements; and the bodies are rendered either magnetic or diamagnetic according to the predominance of one or other of these conditions among their constituent parts. In one respect, the diamagnetic action presents a remarkable contrast to the magnetic, and the difference is

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