Magneto

“ Starting with a nucleus of permanent magnetism, the magneto-electric currents are used, in the first instance, to form a powerful electro-magnet much stronger than the first, and this powerful electro-magnet is again made use of in the same way as the first, in order to give, by means of magneto-electricity, an induced current of very great strength. ”

“ The Magneto and the Dynamo.—Magnetos are used to develop small currents, such as are used for telephone signals, and for operating the sparking devices of gasoline engines. They are therefore found in automobiles containing gasoline motors. The most important device for producing electric currents by electromagnetic induction, however, is the dynamo. It is employed whenever large currents are desired. ”

“ It is probable that amongst arrangements of steam-engines and metal machinery, some curious accidental magneto-electric combinations may be found, producing effects which have never been observed, or, if noticed, have never as yet been understood. ”

“ The softer and more homogeneous is the iron, the more instantaneously will it acquire and lose its magnetism, and the greater strength of magnetism it is able to acquire. An iron bar, round which are wound a large number of turns of insulated or covered wire, constitutes an electro-magnet. Where the magneto and dynamo machines differ. The difference then between a magneto-electric and a dynamo-electric machine is, that in the former permanent magnets are used, and in the latter electro-magnets take their place. ”

“ It is found that if a body be moved before the poles of a magnet in such a direction as to cut the lines of force, electricity is excited in that body, and also around the magnet. The ordinary magneto-electric machines of the shops are illustrations of the application of this property of magnets. They consist essentially in a horse-shoe [Pg 15] magnet, in front of which is caused to rotate, by means of appropriate gearing, or wheel and band, an iron bobbin, or pair of bobbins, coiled with wire. ”

“ Magneto Impulses.—As the magneto gives out impulses of certain intensity at each revolution, which impulses are designed to actuate the sparking mechanism at certain definite periods, it is obvious that the contact breaker must be properly set. ”

“ And whether, conversely, Electricity be or be not directly generated by re-arrangement of the atoms of matter, it is at any rate indirectly so generated through the intermediation of magnetism.
How from Magnetism the other physical forces result, must be next briefly noted—briefly, because in each successive case the illustrations become in great part the obverse forms of those before given. That Magnetism produces motion is the ordinary evidence we have of its existence. In the magneto-electric machine we see a rotating magnet evolving electricity. ”

“ A point highly illustrative of the character of Faraday now comes into view. He gave an account of his discovery of Magneto-electricity in a letter to his friend M. Hachette, of Paris, who communicated the letter to the Academy of Sciences. The letter was translated and published; and immediately afterwards two distinguished Italian philosophers took up the subject, made numerous experiments, and published their results before the complete memoirs of Faraday had met the public eye. This evidently irritated him. ”

“ To make a practical application of the laws governing the production of an induced current, a conductor forming a closed circuit is placed in a magnetic field, and the strength of the field caused to change, alternately becoming strong and weak. In magnetos, the magnetic field is due to two or more powerful steel magnets, and the conductor, a length of insulated copper wire, is wound on a soft iron core and revolved between the poles of the magnets [Pg 256] where the field is strongest. The magnets are known as the field of the magneto, and the wire on its core the armature. ”

“ The secular change is really based on the absolute instruments, the diurnal changes on the magnetographs, and the first idea likely to occur to a critical mind is that the apparent abnormal change on quiet days represents in reality change of zero in the magnetographs. ”

“ Within the co-rotation region, the spinning plasma sets up a powerful electric current girdling the planet.
Charged particles can be accelerated in the magnetosphere to high energies, corresponding to speeds tens of thousands of kilometers per second. Some of these particle streams escape from the inner parts of the magnetosphere and can penetrate the magnetopause and be ejected from the Jovian system. ”

“ Further experiments on this phenomenon have been made by Righi,18 Kundt,19 Du Bois,20 Sissingh,21 Hall,22 Hurion,23 Kaz24 and Zeeman.25 The simplest case is when the incident plane-polarized light falls normally on the pole of an electromagnet. When the magnet is not excited the reflected ray is plane-polarized; when the magnet is excited the plane of polarization is rotated through a small angle, the direction of rotation being opposite to that of the currents exciting the pole. ”

“ It has long been a supposition of mine, that the iron contained in the substance of the globe, has made it capable of becoming, as it is, a great magnet; that the fluid of magnetism perhaps exists in all space; so that there is a magnetical North and South of the universe, as well as of this globe, and that if it were possible for a man to fly from star to star, he might govern his course by the compass; that it was by the power of this general magnetism this globe became a particular magnet. In soft or hot iron the fluid of magnetism is naturally diffused equally ”

“ For both the stone [200] and the magnetick iron arrange themselves by inclination and declination, according to the common position of their nature and the earth. And the force of the earth by the virtue of the whole, by attracting toward the poles, and repelling, arranges all magneticks which are unfixed and loose. For in all cases all magneticks conform themselves to the globe of the earth in the same ways and by the same laws by which another loadstone or any magneticks do to a terrella. ”

“ Some learned men there are who in the course of long voyages have observed the differences of magnetick variation: the most scholarly Thomas Hariot, Robert Hues, Edward Wright, Abraham Kendall, all Englishmen; Others there are who have invented and produced magnetical instruments, and ready methods of observation, indispensable for sailors and to those travelling afar: as William Borough in his little book on the Variation of the Compass or Magneticall Needle, William Barlowe in his Supply, Robert Norman in his Newe Attractive. ”

“ Place the steel bar to be magnetized on a table, or any other convenient place, and, as nearly as possible, north and south, which position is called by philosophers, the magnetic meridian. This being done, draw over it perpendicularly a strong magnet. In this operation, it is necessary to begin at one end of the bar, and draw the magnet over its entire length, and then again in the same direction. It must not be drawn backward and forward, for the power communicated in one direction, would be destroyed by an opposite motion. ”

“ The magnet in its dimensions is perfectly round—a tower of bluish mist shining bright like silver—where it stands in its zone of perpetual darkness; where he made not a light to shine superior to the darkness. And the magnet revolves around perpetually in its protraction, carrying the sun and moon and stars in their circuits over the face of the earth in their roads—in their courses according to their metallic natures—around in a circuit over the parts of the earth, where he designed for his things of life to live. ”

“ The magnetic huts and all that appertained to them were Bernacchi's special business, and many times daily he was to be seen journeying to and fro in attendance upon his precious charge. The general reader may well ask why so much trouble should be taken to ascertain small differences in the earth's magnetism, and he can scarcely be answered in a few words. Broadly speaking, however, the earth is a magnet, and its magnetism is constantly changing. ”

“ To endeavour to reduce our knowledge of these facts to some practical explanation, we must bear in mind that particular spaces around the north and south geographical poles of the earth, are regarded as circles to which all the magnetic lines of force converge. Under circumstances which should prevent any interference with what is called ferro-magnetic action, all bodies coming under that class would arrange themselves according to the laws which would regulate the disposition of an infinite number of magnets, free to move within the sphere of each other’s influence. ”

“ The Austral pole of the Magnet presented within about 4-inches of the forehead of the subject, repulses him and puts him to sleep; while the left hand attracts and awakens him. It is evident, then, that the positive pole of the Magnet and the right hand are poles of the same name; and, if the Austral pole of the Magnet is positive, then the Boreal or Northern pole of the Earth must be negative. The physical laws of the Human Magnetism are consequently identical with those governing the actions of the Magnets. ”

“ A.D. 1683.—Halley (Edmund) , LL.D., who became English astronomer royal, makes known his theory of four magnetic poles and of the periodical movement of the magnetic line without declination. He states that the earth’s magnetism is caused by four poles of attraction, two of them being in each hemisphere near each pole of the earth. By the word pole he means a point where the total magnetic force is a maximum, or, as he himself styles it, “a point of greatest attraction” (Walker, “Magnetism,” p. 317, etc.) ”

“ Bessard, the Frenchman, opines that a magnetick turns toward the pole of the zodiack. Marsilius Ficinus will have it that the loadstone follows its own Arctick pole; but that iron follows the loadstone, straws amber; whilst this perhaps follows the Antarctick pole—a most foolish dream. Others have recourse to I know not what magnetick rocks and mountains. Thus it is always customary with mortals, that they despise things near home, whilst foreign and distant things are dear and prized. But we study the earth itself and observe in it the cause of so great an effect. ”

“ I have said that the cause of direction was twofold, one implanted in the stone and iron, but the other in the earth, implanted by the disponent virtue; and for that reason (the distinction of poles and the verticity in the iron having now been destroyed) a slow and weak directive power is acquired anew from the verticity of the earth. We may see, therefore, with what difficulty and only by the application of hot fires and by long ignition of the iron heated to softness, the imparted magnetick virtue is eradicated. ”

“ Therein he shows, as the result of his customary careful experimental explorations that the magnetism of every known substance (even tissues of the human frame) is manifested in one of two ways. Either the body is, like iron, attracted by the magnet, taking a position coincident with the magnetic forces which he calls paramagnetic (para beside or near, magnetes, magnes, magnet) or bodies—like bismuth, for instance—are repelled by the poles and should therefore be called diamagnetic (dia, across) for they set themselves across, equatorially, or at right angles to the magnetic lines. ”

“ According to the variety and artistick skill in the rubbing of the magnetick iron upon the terrella, so do the magnetick things perform their function more efficiently or more feebly. In motions toward the earth's body, as toward the terrella a variation is displayed due to the unlikeness, inequality, and imperfection of its eminences: So every variation of the versorium or mariners' compass, everywhere by land or by sea, which thing has so sorely disturbed men's minds, is discerned and recognized as due to the same causes. ”

“ I did not see all the events of my life, but only a few of the main ones, which, successively unfolding, passed in review before me on the same visual ray. A magnetism drew me imperiously as with a chain to the Earth; or, if you prefer it, a force similar to that mysterious attraction of the stars, by reason of which, stars of a lesser degree would inevitably fall upon those of the first magnitude, unless retained in their orbits by centrifugal force. ”

“ Happily this does not hinder us from finding out by what law these forces act, and how they enable us to navigate the ocean. I therefore hope the reader will be interested in a short exposition of the very curious and interesting laws on which the science of magnetism is based, and which are applied in the use of the compass.
The force known as magnetic, on which the compass depends, is different from all other natural forces with which we are familiar. It is very remarkable that iron is the only substance which can become magnetic in any considerable degree. ”

“ Therefore, iron or steel objects, such as posts, columns, etc., are permeated by the earth's lines of force, which in the United States enter at the top of these objects and leave at the bottom. The lines of force passing through these bodies arrange their molecules in line or magnetize the bodies. The inductive effect of the earth's magnetism indicates how lodestones or natural magnets acquire their magnetized condition. So far as is known, magnetism produces no effect upon the human body. ”

“ But it very often happens at sea and on land that the magnetick iron does not point to the true pole, and that not only a versorium and magnetick pieces of iron, and the needle of a compass, or a mariners' compass, but also a terrella in its boat, as well as * iron ore, iron stones, and magnetick earths, properly prepared, are drawn aside and deviate towards some point of the Horizon very near to the meridian. For they with their poles frequently face termini away from the meridian. ”