,transcriber's ,note ,italic text displayed as3 italic ,,little ,,blue ,,book ,,no4 #acc ,edited by ,e4 ,haldeman-,julius ,principles of ,electricity ,maynard ,shipley ,,haldeman-,,julius ,,company ,,girard1 ,,kansas ,copyright1 #aibe1 ,haldeman-,julius ,company4 ,,printed ,,in ,,the ,,united ,,states ,,of ,,america ,,principles ,,of ,,electricity ,,contents ,chapter ,page #a4 8,what ,is ,electricity80 #e #b4 ,magnetic ,phenomena #ac #c4 ,pioneers in ,electromagnetic ,theory #ai #d4 ,theories of ,electricity #cj #e4 ,modern ,magnetic ,theory #da #f4 ,proofs that ,electrons ,are ,atoms of ,electricity #dd #g4 ,the ,discovery of ,wireless ,telegraphy #ee ,,principles ,,of ,,electricity ,,chapter #a 8,,what ,,is ,,electricity80 ,many persons who have devoted no time to the study of physics wonder what the force is that drives the street-car along--turning its wheels1 while at the same time furnishing incandescent lamps 7light7 for the passengers4 ,they have been told1 of course1 that the 8power0 used is 8electricity01 generated by dynamos 8at the power-house01 and conveyed to the rapidly moving car by the overhead wire4 8,electricity3 yes1 but what is electricity80 ,this is a natural and perfectly legitimate question for a layman to ask4 ,scientists and philosophers are asking the same question4 ,but they understand quite well that it is like asking3 8,what is matter80 ,very probably the average inquirer does not ask the question1 8,what is electricity80 in the same spirit4 ,we can answer one question no better than the other1 if the ultimate nature of either matter or electricity is what the inquirer has in mind4 ,for matter1 in the last analysis1 is electricity4 ,yet the same person who might ask3 8,what is electricity80 would not think of asking3 8,what is matter80 ,he thinks he knows what matter is--his common sense tells him that matter is what it appears to be4 8,matter's matter1 and there's an end of it40 ,and just so the physicist insists upon his common-sense right to reply3 8,electricity is electricity40 ,it is what it appears to him to be4 ,and it appears to be a form of energy1 or a mode of motion4 ,thales1 the reputed founder of ,greek science and philosophy1 would call electricity 8the soul of the universe01 because it 8endows all things with motion04 ,this 8soul01 interpenetrating all matter--if not constituting it--is by nature always moving--it is self-moving2 motion is part of its very essence4 ,in the lodestone1 said ,thales1 8it moves iron40#a ,as has been said so many times before1 ,thales was the first to call attention to the fact that amber 7fossilized resin71 when rubbed with wool or fur1 possesses the curious property of attracting small particles1 such as straw1 pith1 lint1 dried leaves1 etc42--though there is no reason to suppose that he was the discoverer of this phenomenon4 ,he called the amber elektron2 and today we call the indivisible corpuscles1 or natural unit charges of negative electricity1 electrons--the true atoms of electricity4 ,but hard rubber1 or sealing-wax1 is just as 8mysterious0 as the lodestone 7magnetite--natural magnetic iron74 ,rub the sealing-wax with fur1 and it will exhibit all the peculiar properties of the lodestone4 ,rub glass with silk1 and it1 too1 becomes a lodestone in effect4 ,the ancient ,greek philosophers could not explain these phenomena in precise terms4 ,empedocles 7born between #ejj and #dhj ,b4 ,c47 accounted for the attraction of iron to the magnet on the hypothesis that 8emanations0 or 8effluences0 from the magnet penetrate into the 8symmetrical pores0 of the iron1 drawing the iron itself and holding it fast4 ,the concept 8electricity0 was unknown to the ,greeks4 ,but it is possible that ,empedocles had in mind some such 8effluence0 or 8emanation0 as the 8fluid0 electricity of ,benjamin ,franklin 7#agjf-agij7 and his successors4 ,the soul-force 78moving power07 of ,thales--always moving and causing movement--and the 8effluences0 of ,empedocles have become the 8field of force0 of ,faraday1 ,sir ,j4 ,j4 ,thomson1 and ,sir ,oliver ,lodge4 ,the self-moving 8soul0 of nature1 manifest in the lodestone1 or acting on the lodestone1 or on the particles said to be 8attracted0 by the lodestone1 is but a synonym for the lines of force of the magnetic field of modern physics4 ,thales and ,empedocles spoke in the language 7terminology7 of their day and age4 ,the 8emanations0 of ,empedocles are the 8corpuscles0 of ,thomson--a body becoming positively electrified by 8losing some of its corpuscles01 and hence capable of drawing negatively charged particles to itself4 ,electricity and magnetism are related but not identical4 ,a moving magnet can induce an electric current in a wire1 and an electric current can produce magnetism in iron4 ,the construction of telegraph and telephone instruments depends on the fact that an electric current can produce magnetism and that magnetism can produce an electric current4 ,we know effects which we call 8electricity01 just as we know the phenomena associated with living protoplasm without knowing what 8life0 is4 ,it may be that 8life0 and 8electricity01 as well as 8electricity0 and 8magnetism01 are all different aspects of the same thing4 ,today we say1 in the words of ,dr4 ,charles ,p4 ,steinmetz 78,relativity and ,space01 ,pages #ah-ai73-- 8,the space surrounding a magnet is a magnetic field4 ,if we electrify a piece of sealing-wax by rubbing it1 it surrounds itself by a dielectric or electrostatic field1 and bodies susceptible to electrostatic forces--such as light pieces of paper--are attracted4 ,the earth is surrounded by a gravitational field1 the lines of gravitational force issuing radially from the earth4 ,if a stone falls to the earth1 it is due to the stone's being in the gravitational field of the earth and being acted upon by it40 ,again3--8,suppose we have a permanent bar magnet and bring a piece of iron near it4 ,it is attracted1 or moved2 that is1 a force is exerted on it4 ,we bring a piece of copper near the magnet1 and nothing happens4 ,we say that the space surrounding the magnet is a magnetic field4 ,a field1 or field of force1 we define as #8a condition in space exerting a force on a body susceptible to this field'4 ,thus1 a piece of iron being magnetizable--that is1 susceptible to a magnetic field--will be acted upon2 a piece of copper1 not being magnetizable1 shows no action4444 ,to produce a field of force requires energy1 and this energy is stored in the space we call the field4 ,thus we can go further and define the field as #8a condition of energy storage in space exerting a force on a body susceptible to this energy'40 ,thales said that the 8divine moving power01 the soul of nature1 under certain conditions 8moves iron01 through the mysterious properties of the lodestone4 ,modern science1 borrowing from ,aristotle the term energia1 substitutes for 8soul of nature0 the single word energy4 ,aristotle declared that 8not capacity1 but energy 444 is the first principle anterior to and superior to anything else0 7,metaphysics xii1 #g3 cf4 also ,physics ii1 #i1 #f74 ,modern science describes in more precise phrases what occurs when a body susceptible to the influence of the magnet is brought into proximity to a lodestone 7magnetite74 ,it gives us a picture of 8lines of force0 7energy7 in a defined 8field04 ,but it tells us no more about what energy is than ,thales tells us what his 8moving power0 is4 ,dr4 ,steinmetz tells us that 8energy is the only real existing entity1 the primary conception1 which exists for us because our senses respond to it0 7,op4 cit41 ,page #bc74 ,for ,thales the universal 8moving power0 of nature operates on or in all matter2 for the physicist of today the moving power 7energy7 is matter--man's perception of matter being the response of his senses to the vibrations of energy4 8,all sense perceptions are exclusively energy effects10 and 8energy is the only real existing entity40 ,thales may or may not have considered the cosmos as 8matter0 and 8soul0 or 8moving power04 ,in any event the pre-,socratic ,ionian philosophers recognized no distinction between matter and soul in our modern sense4 ,the moving power of nature 7soul7 was as much a material substance as gross matter itself1 only more rarefied1 more elusive4 ,it was equivalent to the 8energy0--electricity--of modern science4 ,here we have1 then1 the answer to the question3 8,what is electricity80 ,it is energy--8the only real existing entity1 the primary conception1 which exists for us because our senses respond to it40 8,all sense perceptions are exclusively energy effects40 ,this is the answer to the question3 8,what are the ,hertzian waves1 used in #8wireless'80 ,it is the answer also to the question3 8,what is light80 as well as 8,what is electricity80 ,by carrying the explanation of the beam of light and the electromagnetic wave 7like that of the radio communication station or that surrounding a power transmission line7 back to the energy field 7or1 less accurately1 the field of force71 we have carried it back1 as ,dr4 ,steinmetz well declared1 as far as possible1 8to the fundamental or primary conceptions of the human mind1 the perceptions of the senses40 ,all that we know of the world is derived from the perceptions of our senses1 which are for us the only real facts1 all things else being conclusions from them2 and 8all sense perceptions are exclusively energy effects40 ,electricity is an energy effect1 perceived by our senses4 ,no other definition or explanation can or need be given1 since energy is the primary conception4 ,and this explains also what matter is1 since energy and matter are interchangeable--or equivalent--terms4 ,what we call electricity is one of the effects of energy on our senses4 ,in itself1 it is energy1 the stuff that matter is made of2 at once the 8moving power0 and the thing moved4 ,everything has been said that can be said now as to what electricity is3 our concern in the remainder of this volume will be to discover what electricity does and how it acts4 99 99 99 99 99 ,the reader of this little book who may be more or less familiar with larger volumes dealing with electricity1 energy1 electrons1 electromagnetic waves or oscillations1 magnetic and dielectric fields 7usually combined71 light-waves1 etc41 will notice that no mention has been made of the classical ether hypothesis1 the universal plenum in which energy is said to be stored1 and in which transverse waves of light are said to occur1 ether atoms or vibrations moving at right angles 7perpendicularly7 to the light-beam4 ,now1 transverse waves can exist only in rigid 7solid7 bodies4 ,the universal ether of space1 referred to in the text-books1 must--for reasons which ,i need not discuss here--be a solid body of a rigidity much greater than that of steel1 while at the same time possessing a very great elasticity so that bodies 7such as the planets7 moving through it meet with no resistance1 no friction4 ,the electron theory of ,lorentz1 ,larmor1 ,thomson1 ,lodge and others is based upon the assumption that such a plenum1 or medium1 is a real substance4 ,as a matter of fact1 it is not known that any such medium 7or ether7 does exist1 and it is now recognized that while light is a wave1 a periodic phenomenon1 like an alternating current1 it is not necessarily a wave motion of something or in something1 any more than it is necessary to assume the alternating current or voltage wave to be a motion of matter4 ,electrical engineers make no assumption regarding the existence of an ether filling all space and interpenetrating all matter--have no need for an ether as the hypothetical carrier of the electric wave4 ,and just so the physicist of today has no real need for the classical assumption that the light-wave is a wave motion of or in something of great rigidity yet highly elastic and frictionless1 filling all space4 ,light is now known to be a high-frequency electromagnetic wave1 and cannot logically be considered as a wave motion of a hypothetical ether4 8,the ether thus vanishes1 following the phlogistin and other antiquated conceptions40#b ,as ,prof4 ,a4 ,s4 ,eddington remarks in his 8,report on the ,relativity ,theory of ,gravitation0 7#aibj71 8,light does not cause electromagnetic oscillations2 it is the oscillations40 ,we know nothing whatever about the so-called ether of space2 but we can formulate very clearly 8,the ,principles of ,electricity0 without the aid of that hypothesis4#c ,,footnotes3 #a ,if a light piece of iron is placed near a magnet1 it moves to the magnet and clings to it2 but if the magnet is the lighter of the two bodies1 it moves toward the piece of iron4 #b ,steinmetz1 ,dr4 ,charles ,p41 8,four ,lectures on ,relativity and ,space10 ,pages #ba-bb1 ,london and ,new ,york1 #aibc4 ,see ,lecture ,,ii1 8,conclusions from the ,relativity ,theory10 ,pages #ab-de4 ,see also1 ,campbell1 ,dr4 ,norman ,r41 8,modern ,electrical ,theory4 ,supplementary ,chapters3 ,relativity10 ,cambridge ,university ,press1 #aibc4 ,,chapter #b ,,magnetic ,,phenomena ,it was long ago observed that if glass is rubbed by silk1 or a piece of sealing-wax or hard rubber by fur or wool1 an effect occurs similar to that noted by ,thales when amber is rubbed by similar materials--i4 e41 light bodies such as bits of dry paper1 pith1 etc41 will cling to the surface of the substance4 ,after coming in contact with the attracting substance1 the bits of paper1 straw1 etc41 are then repelled4 ,if a ball made of pith be suspended at the end of a silk thread1 and a glass rod which has just been rubbed with silk be brought close to the ball1 the pith-ball immediately flies to the rod1 clinging to it for a time4 ,then it jumps away1 and instead of hanging vertically1 seems to be pushed away from the glass by a mysterious force4 ,a second ball1 treated like the first1 and brought near the first1 is violently repelled4 ,but if one ball is charged from the glass and one from the wax1 they attract instead of repelling each other4 ,two pieces of glass or two pieces of wax repel each other4 ,a similar attraction and repulsion was early observed between the poles of the magnet4 ,this influence seems to be transmitted by some invisible agency or medium across the intervening space between the bodies1 and in this respect the force does not differ from that acting between the moon and the earth1 or the earth and the sun4 ,and just so1 if a light piece of iron is placed near a magnet1 it moves to the magnet and clings to it2 but if the magnet is the lighter of the two bodies1 it moves toward the piece of iron4 ,although ,thales had attempted to explain the cause or nature of magnetic attraction as long ago as the end of the seventh century ,b4 ,c41 or in the first quarter of the sixth century 7about #b1ejj years ago71 it was not until the year #aehb ,a4 ,d4 that ,dr4 ,william ,gilbert 7#aedj-afjc71 of ,colchester1 physician to ,queen ,elizabeth1 made the first experimental study of magnetic phenomena4 ,it is to ,dr4 ,gilbert that we owe the name electricity as applied to this force1 derived from his vis electrica4 ,by #afjj1 ,dr4 ,gilbert had published his epochal work 8,de ,magnete01 which not only contained the first rational treatment of magnetic and electrical phenomena1 but was also virtually the first scientific work published in ,england4 ,it is to this truly great treatise that must be traced the beginnings of the science of electricity4#d ,throwing aside1 as useless1 mere philosophical speculation as to the nature of magnets1 ,gilbert explained in his book how practical experiments should be carried out4 ,he insisted that it is to nature herself that we must apply for the answers to problems in 8natural history04 ,gilbert's particular objective was not1 however1 discovery of the laws of magnetism or electricity2 what he most desired to learn was the composition of the earth3 he wished to know through actual research just what is its innermost constitution4 ,his experiments led him to the conclusion that the earth is a magnet4 ,it may1 indeed1 be considered a huge spheroidal lodestone4 ,gilbert told his readers to take a piece of lodestone 7natural magnetic iron7 of convenient size1 turn it on a lathe to the form of a ball1 then place on the terella 7as he called the spherical lodestone7 a piece of iron wire4 ,it will then be observed that the ends of the wire 8move round its middle point40#e ,lodestones1 fragments of magnetite 7,fe#c,o#d71 are said to have been first discovered at ,magnesia1 in ,asia ,minor1--hence the word magnetism4 ,some of the earliest references to the lodestone relate to its property of lying in a north-and-south direction when an elongate stone is freely suspended1 one particular end always pointing northward1 just as the great magnet the earth1 or the mariner's compass-needle1 has two opposite magnetic poles4 ,the location of the poles of a disk-shaped stone is readily found by turning it round in the presence of a compass-needle4#f ,iron and steel are more strongly magnetic than any other metals4 ,while only one kind of iron ore is naturally magnetic--forming magnets--the property of magnetism may always be given to any kind of iron or steel4 ,one need only strike an iron bar while it is lying in a north-south position1 or rub the iron with a magnet1 and it becomes a magnet4 ,if it is desired to make a permanent magnet1 steel must be employed4 ,a compass-needle is therefore made of magnetized steel4 ,if balanced upon a pivot1 the positive pole of the needle will point 7roughly7 towards the earth's north geographical pole4#g ,a compass-needle is also a 8dipping needle01 unless the suspended magnetized needle lies about half way between the earth's magnetic poles4 ,the north magnetic pole lies below the earth's surface--at an unknown depth--at the extreme northeastern corner of the continent of ,north ,america2 and the corresponding south magnetic pole on the edge of the ,antarctic continent--,king ,george's ,land--about #b1cjj miles south of ,australia4 ,these magnetic poles do not correspond even roughly with the geographic poles1 nor does the magnetic equator by any means correspond with the geographic equator4 ,only a small section of the magnetic equator runs north of the true 7geographic7 equator--e4 g41 from the coast of ,brazil to the coast of ,kamerun 7,africa74 ,according to ,prof4 ,t4 ,j4 ,j4 ,see1 8the whole magnetic system has been pushed southward #bjj miles by bodily displacement of both poles towards the ocean hemisphere40 ,this eminent physicist-astronomer also stated 7in #aibb7 that his researches led him to the discovery that the two magnetic poles are at unequal depths in the earth1 the ,north ,pole being much deeper than the ,south ,pole1 8with the result that the total magnetic forces in the southern hemisphere are considerably stronger than in the northern hemisphere40#h ,it was long ago discovered that if one starts northward from the magnetic equator1 the compass-needle soon begins to dip downward 7and northward74 ,at the southern border of the ,united ,states1 the downward inclination amounts to about #eg degrees4 ,at the borders of ,north ,dakota and ,maine the dip is about #gf degrees4 ,by the time ,hudson ,bay is reached the needle assumes a vertical position4 ,this means that it is here suspended immediately over the north magnetic pole itself4 ,at the magnetic equator in ,peru1 a needle suspended by a thread is exactly balanced4 ,dr4 ,see states that at the ,north and ,south ,poles there is a downward pull--by the magnetic force--of just one millionth of the gravitational force1 while in ,peru the total magnetic force is precisely one ten millionths of gravitation4 ,it has been found that both the ,north and the ,south ,poles are anything but fixed in position4 ,they 8wander about in their subterranean region04 ,in the course of centuries1 the compass-needle swings from west of north1 and then to the east4 ,even the amount of the dip slowly changes1 in a periodic way1 and at every point on the earth4 ,for example1 in #aegf1 the north end of the needle at ,london dipped at an angle of #ga degrees #ej minutes4 ,by #agbj the angle had increased to #gd degrees #db minutes--almost up and down4 ,since then1 the dip at ,london has continually decreased4 ,at the present time we are puzzled by the fact that the inclination of the dip is #ff degrees at ,london and more than #gj degrees at ,washington4 ,it has long been known that variations in magnetic declination of the delicately mounted needles1 in observatories1 are directly correlated with solar disturbances4 ,the late ,dr4 ,a4 ,wolfer 7sometime director of the ,zurich ,observatory7 was the first to show us how closely the curve of the sun-spot activity rises and falls with the fluctuations of magnetic declinations4 ,before attempting to explain the peculiarities of magnetic action in terms of the modern electromagnetic theory1 it will be well to recall certain stages of progress in the development of this theory4 ,this plan will permit elucidation of the theory itself by 8easy steps04 ,,footnotes3 #c ,cf4 ,whittaker1 ,e4 ,t41 8,a ,history of the ,theories of the ,ether and ,electricity from the ,age of ,descartes to the ,close of the ,nineteenth ,century10 ,dublin and ,london1 #aiaj4 ,see also1 ,comstock and ,troland1 8,the ,nature of ,matter and ,electricity10 ,new ,york1 #aiag2 ,steinmetz1 ,dr4 ,charles ,p41 8,elementary ,lectures on ,electric ,discharges1 ,waves and ,impulses and ,other ,transients10 ,new ,york1 #aiad2 and ,starling1 ,dr4 ,sydney ,g41 8,electricity10 ,london and ,new ,york1 #aibb4 #d ,on the ,continent1 experimental work in other fields was already in progress1 thanks to the genius of ,descartes1 ,galileo and other founders of modern science4 ,gilbert1 like ,harvey1 spent some years in ,italy1 coming under the direct influence of the great ,italian physicist-astronomer-physician ,galileo4 ,harvey was in ,padua 7#aeih-afjb7 during ,galileo's professoriate4 ,the introduction of scientific methods in ,england at this time may well be credited to ,italian and ,french influences4 #e ,gilbert's book is usually referred to simply as 8,the ,magnet10 but the full title is3 8,concerning the ,magnet and ,magnetic ,bodies1 and ,concerning the ,great ,magnet the ,earth3 ,a ,new ,natural ,history 7,physiologia7 ,demonstrated by ,many ,arguments and ,experiments40 #f ,magnetite does not always possess polarity4 ,it is called 8lodestone0 only when it does4 ,it occurs not only in the form of more or less massive stones1 but also as loose sand and in earthy forms4 #g ,the fact that a lodestone possesses two 8poles0 was discovered in the thirteenth century by ,petrus ,peregrinus1 of ,picardy1 while he was experimenting with a spherical lodestone and a needle4 #h ,from notes taken at a lecture by ,dr4 ,see before the ,california ,academy of ,sciences in #aibb4 ,dr4 ,see1 in charge of the ,united ,states ,naval ,observatory at ,mare ,island 7,california71 presented in the lecture 8,a ,new ,theory of the ,ether10 in which he outlined the grounds upon which he based his new theory of a direct connection between magnetism and universal gravitation4 ,it is highly interesting1 in this connection1 to learn that ,dr4 ,albert ,einstein1 in collaboration with ,professor ,eddington 7of ,cambridge7--working on the principle of ,relativity--has discovered a connection between the earth's power of attraction 7gravitation7 and electricity4 ,,chapter #c ,,pioneers ,,in ,,electromagnetic ,,theory ,the ,danish physicist1 ,hans ,christian rsted1 professor of natural philosophy at the ,university of ,copenhagen1 showed us1 more than a century ago1 that a magnetic needle can be deflected by an electric current4 ,he had been led by theoretical considerations to assume that there must be a correlation between electric and magnetic forces4 ,while yet a young man1 rsted endeavored by persevering experimentation to prove the correctness of his theory4 ,while he did not expect a parallel action of the two forces1 he was firmly convinced that magnetism and electricity were inseparable twins4 ,he noted that both heat and light radiated from a conductor when heated to incandescence4 ,he also assumed that magnetic forces are radiated from a conductor traversed by electricity4 ,in #ahbj1 while lecturing before his class1 he became convinced that the apparatus he was then using could be made to demonstrate the correctness of his views4 ,he asked his pupils to accompany him to his laboratory1 where1 as he predicted1 a slight deflection of the magnetic needle1 turned at right angles to the electric current1 was shown when placed close to the copper wire4 ,some months afterwards1 with a stronger current 7made up of twenty cells71 he obtained much more intense effects4 ,investigating these in detail1 he found that they met all the requirements of his theory4 ,so1 on ,july #ba1 #ahbj1 he sent out to the scientific world his now famous circular1 8,experimenta circa effectum conflictus electrici in acum magneticum0 7,experiments on the effect of the electrical conflict in the magnetic needle74 rsted showed1 furthermore1 how changes in the position of the magnetic needle occurred with variation of the position of the conductor 7copper wire7 in regard to it4 ,he demonstrated also that the magnetic effect was not weakened by insulators--that it would penetrate various materials1 whether these were conductors of electric currents or not4 ,he showed that the magnetic field created by the electric current does not have any influence on a needle of non-magnetic material--i4 e41 brass1 glass1 etc4 ,it is1 in fact1 chiefly in the fact that it cannot be insulated that magnetism differs from electricity4 ,it will freely pass through air1 stone1 mica1 glass1 clay1 brick1 or any insulating material4 ,it is well worthy of especial mention that rsted employed the term 8conflictus0 to designate the electric current1 many decades before the origin of the electron theory of matter4 ,for1 on modern theories of electricity1 it is the movement to and fro of electric particles 7electrons7 through the conductor1 and their impact 78conflictus07 that produces what we call electrical phenomena4 rsted's fundamental discovery of the mutual effects between electricity and magnetism led to further discoveries which made possible the construction of telegraph and telephone instruments1 since these depend on the fact that an electric current can produce magnetism1 and that magnetism can produce an electric current4 ,if we wind around an iron bar a number of turns of insulated wire1 and an electric current is allowed to pass through the coil1 the bar becomes a strong electromagnet4 ,but it remains a magnet only as long as the current is passing4 ,now1 the magnetic effects obtained with the electromagnet are identical with those obtained from a permanent magnet--such as the familiar horseshoe magnet1 commonly seen on the flywheel of the ,ford automobile1 or in the ordinary telephone generator for calling up 8,central04 ,in the case of a telegraph instrument1 it is important that the iron is a temporary magnet4 ,on the other hand1 a permanent magnet is an essential part of every ,bell telephone receiver4 ,this permanency is secured by employing a bar of steel instead of a piece of iron--a temporary magnet4 ,the power produced from a dynamo--or electric generator--depends upon the fact that when a magnet is put into a coil of wire1 only a momentary current of electricity passes through the wire1 in one direction4 ,if the magnet is withdrawn1 a current starts in the opposite direction4 ,copper wire coiled about an iron core forms the 8armature0 of the dynamo4 ,the rotating coils are said to 8cut the magnetic field40 ,on this principle of electricity1 intense electric currents are produced1 furnishing the 8power0 for the electric motors in electric cars1 elevators1 musical instruments1 etc41 and for electric lights--incandescent and arc4 ,dynamos may contain either permanent magnets or electromagnets4 ,they produce the magnetic field in which the 8armature0 or conductor--the coils of wire wound around the iron core--rotates4 ,a machine with permanent magnets is usually termed a magneto1 and is never made in large sizes4 ,the current for the electromagnets may be derived wholly from an outside source1 or part of the current which it generates may be used for that purpose4 ,the current generated in the armature winding is alternating1 but may be rectified to a direct current by a commuter if desired2 otherwise it is conveyed to the line circuit by collector or slip rings and brushes4 ,we owe much of our knowledge of magnetism and electricity to ,michael ,faraday 7#agia-ahfg71 who brilliantly covered the whole field of these sciences4 ,faraday was distinguished alike as a chemist and as an experimenter in electricity and magnetism4 rsted had shown that magnetism could be produced by a current of electricity1 but it remained for ,faraday to produce current electricity by a magnetic 8field of force01 thus laying the foundation for those modern industries which derived motive force for their machinery from the gigantic dynamos of our 8power houses04 ,but ,i must here introduce a few facts concerning the contributions to electric theory and practice of the great ,french mathematician and physicist1 ,andr ,marie ,ampre 7#agge-ahcf74 ,his discoveries in electrodynamics aided greatly in laying a broad foundation for this science4 ,very notable was the influence exercised by ,ampre on the development of electrodynamics4 ,and it was he who first clearly established the fact that magnetic action is a peculiar form of electromotive action1 and that1 in phenomena of this class1 8action and reaction are equal and opposite40 ,from these considerations it was natural for him to suppose that magnetism might be made to produce electricity1 as it had already been shown that electricity might be made to imitate all the effects of magnetism4 ,numerous attempts were made to effect this predicted result1 but for some years all such efforts proved to be fruitless4 ,meanwhile the ,french physicist and astronomer1 ,franois ,arago 7#aghe-ahec71 was also conducting experiments with the object of producing electricity by magnetism4 ,one of his experiments actually involved the effect sought1 but it was not clearly recognized4 ,arago observed that the rapid revolution of a conducting plate in the neighborhood of a magnet gave rise to a force acting on the magnet4 ,but it was not recognized by either ,arago or other physicists of the day that the forces involved were electric currents--produced by the rapidly revolving conducting plate4 ,faraday1 in #ahca1 after several years of preoccupation with other problems1 returned to his task of discovering electrodynamical induction1 begun in #ahbe4 ,after a number of fruitless efforts1 he was finally rewarded with success1 but not in the form which had been anticipated4 ,it was observed that at the precise time of making or breaking the contact which closed the galvanic circuit1 a momentary effect was induced in a neighboring wire1 which1 however1 disappeared instantly4#i ,faraday then discovered that a similar effect could be induced merely by moving the wire nearer to or farther away from the closed circuit--instead of suddenly making or breaking the contact of the 8inducing circuit04 ,later he found that the effects were increased by the proximity of soft iron1 and that when the soft iron was affected by an ordinary magnet instead of the voltaic wire1 the same effect still recurred4 ,the momentary electric current was produced either by moving the magnet or by moving the wire with reference to the magnet4 ,finally1 it was found that the earth itself might be substituted for a magnet1 not only in this experiment but also in others4 ,mere motion of a wire1 under proper conditions1 produced the effect4 ,here1 then1 was the true explanation of ,arago's experiment3 by the rapid revolution of the plate the momentary effect became continuous4 ,without using the magnet1 a revolving plate became an electrical machine4 ,a revolving globe was found to exhibit electromagnetic action1 the circuit being complete in the globe itself without the addition of any wire4 ,it was later found by ,faraday that mere motion of the wire of a galvanometer produced an electrodynamic effect upon the needle4#aj ,meanwhile1 ,ampre1 8by a combination of mathematical skill and experimental ingenuity1 first proved that two electric currents act on one another1 and then analyzed this action into the resultant of a system of push-and-pull forces between the elementary parts of these currents40#aa rsted having shown that electric currents produced certain effects on magnets without being in actual contact1 and ,ampre having demonstrated that magnets can in their turn be supplemented by electric currents1--a magnetic needle being deflected not only by a current passing through a wire1 but also by another magnet brought into its neighborhood1 and two electric currents acting on one another at a distance--the question now arose as to whether or not electrical attraction and repulsion could be reduced to an action at a distance proportional to the inverse square of the distance4 ,as early as #aggc1 ,henry ,cavendish 7#agca-ahaj7--one of the foremost chemists and experimentalists of his day--answered this question affirmatively by experiment4#ab ,coulomb 7#agcf-ahjf7--;inventor of the torsion balance--showed that ponderable matter charged with electricity followed the same formula for attraction and repulsion as gravitating bodies did4 ,poisson 7#agha-ahdj7 worked out the difficult mathematics of fluids actuated by repelling forces depending on the inverse square of the distance4 ,laplace 7#agdi-ahbg7 had very early become convinced that the actions of ponderable substances in which electric currents were flowing could be reduced to an action at a distance proportional to the inverse square of the elements of the electric current4 ,faraday regarded the electric field as full of lines of electric force1 in a state of tension1 and naturally repelling each other4 ,to him1 as to a number of his contemporaries1 the idea of 8action at a distance0 was repugnant2 though such a possibility seemed to be indicated by the action of gravitation--the relation of the forces between two charged bodies to the distance between them being very similar to that of the gravitational forces between two bodies to the distance between them4 ,but ,faraday1 like the great ,descartes long before him1 rejected the theory of action at a distance in favor of 8action through a medium40 ,ampre had sought for some sort of mechanism for the transmission of electromagnetic currents4 ,his own discoveries and those of rsted led him to formulate the hypothesis that the field in the vicinity of a magnetic body is produced by a number of exceedingly small circular currents which flow undamped in or around the molecules and that magnetization consists merely of the bringing of these molecular currents into a parallel direction4 ,but it was difficult for some physicists1 even in ,ampre's day1 to accept the hypothesis of undiminished currents possessing no resistance4 ,if we transform the idea of the 8molecular currents0 of ,ampre into the language of today1 substituting for these molecular currents electrons revolving in atoms1 it can be shown that the great ,french scientist was substantially correct in his assumptions4 ,in #aiae ,dr4 ,albert ,einstein and ,w4 ,j4 de ,haas astonished the world of physicists by showing experimentally--by means of a most ingenious apparatus--that the 8molecular currents0 or revolving electrons really exist4 ,in #aiai1 ,professor ,kramerlingh-,onnes1 at the ,university of ,leyden1 was able to produce what he called imitations of ampere currents--i4 e41 8undiminished currents producing no resistance40 ,it was demonstrated that the resistance of pure gold and pure platinum differ very little if at all from nil at low temperatures4 ,but wires of these metals1 of absolute purity1 are difficult to obtain1 so mercury was selected for the experiments4 ,the resistance of the metal at the lowest attainable temperature of liquefied helium1-#bga4e ,c41 7at a pressure of #c mm4 of the mercury column71 proved to be immeasurably small4 ,the resistance down to a position shortly below #d4b ,k4 7,kelvin's absolute scale7 suddenly dropped from a measurable amount to a value practically nil4 ,it was found that the induced current remained in a state of circulation1 and that the decrease in the strength of the current amounted to less than #a per cent per hour1 from which it followed that the 8time of relaxation0 must amount to more than four days6#ac ,at the absolute zero of temperature1 it is supposed that the orbits of electrons in atoms are perfect circles1 whatever their paths may be at measurable temperatures4 ,this motion of the electrons remains when all heat has disappeared1 since it is not this motion of the revolution of the electrons in their orbits that is associated with the energy of heat4 ,heat is a mode of motion of the atoms themselves1 not of their contained electrons2 though increase of heat doubtless results in an increase in the average orbital velocity of the electrons4 ,since ,ampre's day we have learned at all events1 that an electric current means the flow of electrons1 either from atom to atom1 or passing between the atoms1 along conductors4 ,in #aibj1 ,lord ,kelvin came to the conclusion that at the absolute zero resistance of metals must be infinitely great1 the degrees of dissociation of the electron being1 he supposed1 nil at the zero hour4 ,if any free electrons remained1 he believed they would lose their power of motion1 condensing like a vapor upon the metal atoms and freezing fast to them 7to borrow a phrase from ,kamerlingh-,onnes74 ,the experiments of the celebrated ,holland physicist show that the resistance of metals decreases with lowering of temperature1 and would probably become nil at the absolute zero with employment of a perfectly pure platinum wire4 ,if this is true1 then would a current of electricity1 once set up in a conductor1 continue forever8 ,,footnotes3 #i ,philosophical ,transactions1 ,page #abg1 #ahcb2 ,first ,series1 ,article #aj4 #aj ,one of the first electrical experimenters to devise the instrument known as a 8galvanometer0 was ,professor ,schweigger1 of ,halle4 ,there are now eight or more varieties of this instrument 7or apparatus7 in use4 ,it enables the investigator to measure extremely minute electrodynamic actions1 or the very weakest intensity of an electric current1 as well as to detect its presence or direction1 usually by the deflection of a magnetic needle4 #aa ,maxwell1 ,clerk1 8,on ,action at a ,distance10 7,scientific ,papers1 ,vol4 ,,ii1 ,page #cag74 #ab ,the scientific papers of ,cavendish were published 7in #ahgi7 under the title1 8,the ,electrical ,researches of the ,hon4 ,henry ,cavendish10 edited by ,clerk ,maxwell4 ,cavendish anticipated many later investigations of ,british and ,continental writers1 including ,ohm's law--i4 e41 the proportionality between the electromotive force and the current in the same conductor2 and anticipated also ,faraday's discovery of the specific inductive capacity of different substances1 even measuring its numerical value in several substances4 ,he had also arrived at the conceptions of electrical capacity and of 8potential40 #ac ,see ,die ,naturwissenschaften 7,berlin71 ,january #bh1 #aiba4 ,,chapter #d ,,theories ,,of ,,electricity ,the science of electricity is based upon observation of those phenomena of attraction and repulsion which are comprehended under the term electrostatics4 ,statical electricity1 so named from a ,greek word 7statikos71 which means 8causing to stand 7or stay710--also called frictional electricity--is the electricity of stationary charges caused by rubbing together unlike bodies1 such as glass and silk 7noted in ,chapter ,,ii74 ,in such cases equal and opposite charges of electricity are always produced4 ,the term statical electricity applies properly1 however1 to the electricity of all stationary charges1 however produced4 ,the electricity upon the surface of glass is called positive electricity2 that upon rubber1 negative electricity4 ,when silk is rubbed upon glass it receives a negative charge from the glass and confers a positive charge upon the silk4 ,wool or fur rubbed on wax or rubber receives a positive charge in exchange for a negative charge2 8equal and opposite charges of electricity are always produced40 ,a piece of glass and a piece of silk attract one another2 two pieces of silk or two pieces of glass or wax repel one another1 because a body which is positively charged is attracted by one negatively charged and repelled by one negatively charged1 and vice versa4 ,a piece of glass rubbed by a piece of silk1 under suitable conditions1 attracts any other body with which it has not been in contact4 ,the piece of silk will do likewise4 ,in all these cases1 the attraction or repulsion becomes weaker with increase of distance between the attracting and repelling bodies4 ,a third body which has been in contact with a piece of glass or a piece of silk acquires to some extent the properties of the glass or silk with which the third body has been in contact4 ,and1 conversely1 the glass or silk with which the third body has been in contact attracts or repels with less force than before4 ,if a hand is drawn over the surface of an object after it has been charged with electricity1 the electricity disappears4 ,it has been conducted through the hand and the body to the earth4 ,this phenomenon shows that the human body is a conductor of electricity4 ,but most metals are much better conductors4 ,moist air and damp wood are rather poor conductors1 while dry air1 dry wood1 porcelain1 glass1 hard rubber and sealing-wax are non-conductors1 or insulators4 ,the term dielectric is used in preference to insulation when reference is made to the property of transmitting induction--a process quite distinct from ordinary transmission of an electric current4 ,in electrostatic induction1 a body electrostatically charged induces in a neighboring conductor a like charge in the parts farthest from the charged body1 and an unlike charge in the nearer parts2 the repelled like charge being removed by connecting any part of the conductor momentarily with the earth1 while the bound unlike charge spreads over the whole surface of the conductor and remains there even when the inducing body is moved away1 or its charge neutralized1 if the conductor is properly insulated4 ,dielectric strength refers to the ability of an insulating material to resist rupture by high voltage1 measured by the voltage necessary to effect a disruptive discharge through it4 ,insulation resistance1 on the other hand1 refers to the ohmic resistance offered by an insulating material to an impressed voltage1 tending to induce a breakage of current through it4 ,the term dielectric is used as a synonym for insulator1 in the sense that a charge on one part of a non-conductor is not communicated to any other part4 ,a charge given to a conductor spreads to all parts of the body4 ,a dielectric possesses the property of transmitting electric force by induction but not by conduction4 ,a charge on one part of a non-conductor or dielectric is not communicated to any other part4 ,jeans suggests that since the presence of magnetic energy is always associated with charges in motion1 whereas electrostatic energy is present when all the charges are at rest relatively to each other1 it may be proper to identify electrostatic energy with potential energy1 and magnetic energy with kinetic energy#ad--;i4 e41 energy due to motion of particles1 rather than to energy of position1 as of a coiled spring4 ,statical energy is distinguished from 8current electricity0 by the fact that it accumulates on various bodies--is stored up--and as soon as proper connections are made1 it discharges instantly4 ,statical electricity is used by physicians in electrical treatment of diseases and in ,x-ray work4 ,machines have been constructed that will produce very strong charges of statical electricity4 ,if a sufficiently large charge of electricity accumulates upon an insulated conductor in an electrical machine1 it finally discharges itself1 passing through the air to the nearest body4 ,a flash of lightning is the result of an overcharge of statical electricity accumulated upon cloud particles1 and may pass from cloud to cloud or descend to the earth4#ae ,careful drivers of gasoline-tank wagons allow an iron or steel chain to drag on the roadway from a metallic connection1 which conducts any surplus 8static0 to the ground4 ,failure to provide for such an emergency sometimes results in a terrific explosion with consequent loss of life4 ,about the beginning of the nineteenth century1 the ,italian scientist1 ,alessandro ,volta 7#agde-ahbg71--;and other physicists--discovered what has been called1 after ,volta1 voltaic electricity1 a current generated by chemical action between metals and different liquids as arranged in a voltaic battery4 ,the term 8volt0--the electromotive force which performs work at the rate of one joule per second 7one watt7 in producing a current of one ampere--was similarly derived4 ,it was learned that if two different metals1 such as copper and zinc amalgam1 are placed in a weak acid solution 7such as one part ,h#b,,so#d to four parts ,h#b,o71 and connected by a wire fastened securely to the metals1 a current of electricity 7about two volts7 will pass through the wire4 ,carbon 7a non-metal7 and a metal upon which the solution acts chemically may be used instead of two metals4 ,there must be chemical action between the liquid and one metal1 or there will be no current4 ,such a combination constitutes a cell1 and two or more cells make a battery4 ,the current starts with the zinc1 is conducted by the solution to the copper1 and thence by wire back to the zinc1 completing a circuit4 ,the zinc constitutes the negative pole 7or electrode71 the copper or carbon the positive pole 7or electrode74 ,a cell frequently employed1 where a weak 7about #a4a volts7 but constant electromotive force 78,e4 ,m4 ,f407 is required1 is one devised by the ,english physicist1 ,john ,d4 ,daniell 7#agij-ahde74 ,in this cell a copper sulphate solution containing a copper electrode is placed in contact 7by means of a porous wall or partition--usually an unglazed porcelain cup7 with a zinc sulphate solution containing a zinc electrode4 ,the zinc electrode is negative to the copper4 ,at each electrode there exists a potential difference between solution and electrode4#af ,the two electrodes being connected externally by a wire1 a current of electricity will flow through the wire from the copper to the zinc1 and zinc will dissolve at the anode 7positive pole7 and copper deposited on the cathode 7negative pole74 ,the current in this case1 as in the preceding1 is said to be produced by voltaic action and the cell is a primary battery4 ,voltaic action and electrolysis--the process of chemical decomposition 7or dissociation of compounds or molecules7--by the action of an electric current produced externally 7as by a dynamo7 and forced through the cell1 are essentially identical phenomena1 and obey the same laws4#ag ,the familiar dry cell contains no liquid which might be spilled1 and is very useful for certain purposes1 as in automobiles1 and in operating door-bells4 ,it is merely a voltaic cell whose chemical contents are made practically solid 7or paste-like7 by the use of some absorbent1 as gelatine1 sawdust1 etc4 ,in cells of the ,leclanch type1 a mixture of plaster of ,paris1 flour1 and sal ammoniac takes the place of the solution which acts chemically upon one of the contained metals4 ,when used up1 a dry cell must be replaced by an entirely new cell4 ,two or more dry cells constitute a dry battery4 ,we have seen that there are two types of charged bodies1 of which charged glass and charged silk are familiar examples4 ,it was ,dufay 7#afii-agci7 who discovered that there were two kinds of electricity1 one of which he called vitreous 7from glass7 and the other resinous 7from resin--amber74 ,the terms 8positive0 and 8negative0 in relation to electricity were first applied by ,benjamin ,franklin1 in #agef4 ,to the electricity of the glass rod ,franklin gave the name 8positive0 and to that of the sealing-wax 7or hard rubber1 amber1 etc47 the name 8negative40 ,these names are now universally in use--though ,french physicists still speak of vitreous and resinous electricity4 ,i have spoken also of a positive pole 7or electrode7 and a negative pole 7or electrode74 ,the electrodes constituting the two poles of a current are also called the anode and the cathode1 the former being the positive electrode and the latter the negative electrode4#ah ,when it was learned that electrical charges could be distinguished by two opposing terms--positive and negative--it was natural to suppose that there were two distinct kinds of electricity1 or 8fluids40 ,this was the view taken by the ,french chemist ,dufay4 ,but the ,german electrician pinus 7#agbd-ahjb71 in his great pioneer work1 8,tentamen ,theoriae ,electriciatis et ,magnetismi0 7,an ,attempt at a ,theory of ,electricity and ,magnetism--#agei71 considered the mathematical consequences of the hypothesis of a single fluid1 attracting all matter but repelling itself4 ,it soon became apparent1 however1 that he must assume either the existence of two electrical fluids or the mutual repulsion of material particles4 ,he chose the latter theory4 ,he explained the phenomena of the opposite poles as results of the excess and deficiency of a 8magnetic fluid10 which was dislodged and accumulated in the ends of the body1 by the repulsion of its own particles1 and by the attraction of iron and steel1 as in the case of induced electricity4#ai pinus1 who was unquestionably one of the greatest physicists of the eighteenth century1 devised a method of examining the nature of the electricity at any part of the surface of a body1 by which means he was enabled to ascertain its distribution4 ,he found that the distribution was in agreement with the attractions and repulsions which objects exert when they are in the neighborhood--8electrical atmosphere0--of electrified bodies4 ,today we say that such bodies are electrified by induction4 ,the pinian theory of electricity and of magnetism was modified and presented in a new form 7in #aghh7 by ,coulomb1 with two fluids instead of one4 ,his first task1 before reducing the theory to calculation1 was to determine the law of the forces involved--not being satisfied1 for example1 with ,newton's assumption that the attractive force of magnetism is inversely to the cube of the distance4 ,mayer in #agfj1 and ,lambert a few years later1 had found the law to be that of the inverse square4 ,coulomb desired experimental confirmation of this law before accepting it as established4 ,this he secured by means of his torsion-balance 7about #aghd74bj ,it was in pursuance of this investigation that ,coulomb brought to light for the first time the fact that the directive magnetic forces which the earth exerts upon a needle is a constant quantity1 parallel to the magnetic meridian1 and passing through the same point of the needle whatever be its position4 ,barlow1 who had adopted the two-fluid hypothesis1 showed that the magnetic 8fluids0 were collected at the surface of spheres 7of iron71 the surface being the only part in which there could be detected any magnetism4 ,he demonstrated that a shell of iron produces the same effect as a solid ball of the same diameter4 ,poisson's later analysis 7#ahbd7 showed that this was a consequent to be expected4 ,merz has well said that what ,laplace did for ,newton was done by ,poisson 7#agha-ahdj7 8for ,coulomb's elementary law of electric and magnetic action1 and on a still larger scale by ,gauss1 who worked out the mathematical theory and applied it to the case of the magnetic distribution on the earth's surface4 ,in ,england1 already before ,coulomb's researches were published1 ,cavendish had1 likewise by a combination of experiment and calculation1 established the elementary formulae and properties of electrical phenomena40#ba ,benjamin ,franklin1 the first ,american to gain international renown as a scientist1 adopted and developed a 8one-fluid theory of electricity40 ,on this supposition the parts of the fluid repel each other1 and the excess in one surface of the glass--for example--repels the fluid from the other surface4 ,the fluid itself was regarded by ,franklin as positive1 the part of the other 7negative electricity7 being taken by ordinary matter1 the particles of which were supposed to repel each other and attract the positive fluid1 just as the particles of the negative fluid did on the two-fluid theory4 ,on both the two-fluid and the one-fluid theories1 as we have seen1 the particles of the positive fluid repelled each other by forces varying inversely as the square of the distance between them--as shown by both pinus and ,coulomb4 ,this is true also of the particles of the negative fluid4 ,the particles of the positive fluid attracted those of the negative fluid4 ,in ,franklin's one-fluid theory it was the ordinary particles of matter which attracted the positive fluid and repelled one another4 ,both theories from their very nature imply1 as ,sir ,j4 ,j4 ,thomson long ago 7#aijf7 pointed out1 the idea of action at a distance4 ,in his very interesting book1 8,matter and ,energy0 7#aiab71 ,professor ,soddy says3 8,all electrical phenomena can be explained as well on the one-fluid as on the two-fluid idea1 but our ignorance at the present time as to whether there are two kinds of electricity or one is fundamental4 ,until the question is settled1 the hopes that have been entertained that1 through the study of electricity1 we shall be able to arrive at a philosophical explanation of matter1 are likely to prove unfounded40 ,our modern view of electrification bears a close resemblance to the one-fluid theory of ,franklin1 whether we suppose there is one kind of electricity1 or two kinds4 ,at all events1 if there be such a separate force1 or such units of energy1 as 8positive0 electricity1 it has never been isolated1 as have been the negative atoms or electrons4 ,negative electrification is but a collection of these negative corpuscles or unit charges4 ,the particles of the 8electric fluid0 of ,franklin correspond to these electrons4 8,instead of taking1 as ,franklin did1 the electric fluid to be positive electricity1 we take it to be negative10 says ,j4 ,j4 ,thomson1 in his 8,corpuscular ,theory of ,matter0 7#aijf74 ,and 8the transference of electrification from one place to another is effected by this motion of corpuscles from the place where there is a gain of positive electrification to the place where there is a gain of negative4 ,a positively electrified body is one that has lost some of its corpuscles40#bb ,,footnotes3 #ad ,jeans1 ,j4 ,h41 8,electricity and ,magnetism10 ,page #dhc1 #aiaa4 #ae ,benjamin ,franklin was first to show 7in a letter to ,peter ,collinson1 written ,october #ai1 #ageb7 that lightning and electricity are one and the same thing4 ,he was also inventor of the lightning-rod4 #af 8,potential0 is analogous to level 7or pressure7 in hydrostatics or mechanics4 #ag ,for further explanation1 see ,shipley1 ,maynard1 8,the ,a4 ,b4 ,c4 of the ,electronic ,theory of ,matter10 ,little ,blue ,book ,series1 ,no4 #fjc4 #ah ,see1 in this connection1 ,shipley1 ,op4 cit4 #ai ,a very similar hypothesis was read before the ,royal ,society by ,henry ,cavendish1 in #agga1 the work of pinus being unknown to him at the time4 #bj ,by means of this instrument very minute forces can be accurately measured1 such as electrostatic or magnetic attraction and repulsion1 by the torsion 7turning or twisting7 of a wire or filament1 the angle of torsion being proportional to the amount of force exerted4 #ba ,merz1 ,henry1 8,history of ,european ,thought in the ,nineteenth ,century10 ,vol4 ,i1 ,page #cfb4 #bb ,for a recent work on modern electrical theory1 see ,starling1 ,sydney ,g41 7head of the department of physics in the ,west ,ham ,municipal ,college1 ,london71 8,electricity10 ,london1 #aibb4 ,for the pioneer work of ,ampre1 see his 8,theorie des ,phenomenes ,electrodynamiques10 #ahbf4 ,,chapter #e ,,modern ,,magnetic ,,theory ,we have already shown how the magnetism of a magnet is converted into electricity1 by means of rotating coils cutting the lines of magnetic force in the 8field40 ,the energy used to drive the machinery may1 of course1 be derived either from water-power or by steam4 ,gravity gives energy to falling water2 chemical energy produced by the oxidation of coal becomes heat energy1 which in turn causes the expansion of steam1 which produces energy of motion in a piston2 and this motion1 transmitted to the parts of an engine to a dynamo1 produces electrical energy4 ,when the electric current from the dynamo has been conducted to any desired point by cables1 another motor1 acting in the opposite sense1 causes the electricity to change back again into the original mechanical energy1 less the loss due to imperfections in the operation4 ,here we have1 then a clear picture of what is meant by the phrase1 transformation of energy4 ,but another question naturally arises at this point4 ,we know that with a finite quantity of magnetism we can produce an unlimited quantity of electricity4 ,yet we add no new material1 no source of supply1 to the dynamo4 ,let the rotating coils continue to cut the lines of magnetic force in the magnetic field1 and the magnetism of the magnet will be transformed into current electricity--furnishing a literally exhaustless supply from the great storehouse of nature4 ,for us the energy of the universe is infinite in quantity4 ,the reservoir of energy is exhaustless1 and the dynamo is man's open sesame4 ,but just here the very interesting question arises3 ,is the inexhaustible supply of electric current with the expenditure of a limited quantity of magnetism fully explained by saying that it is due to the rotational movement of the coil8 ,can the mere rotation of a metal in a magnetic field actually create an endless supply of available energy8 ,not likely6 ,as ,dr4 ,gustave ,le ,bon well says3 8,such a metamorphosis would be as marvelous as transformation of lead into gold by simply shaking it in a bottle4 ,another interpretation must be sought for the phenomenon40 ,now1 a current of electricity is known to be a stream of electrons 7negative charges7 flowing along or in a conductor2 and an electron is an atom of--energy4 ,but where was this energy stored8 8,in the all-pervasive ether10 say many physicists4 8,there is no ether10 say others4 ,the electromagnetic field represents energy storage in space--not in a universal1 incomprehensible1 paradoxical something called 8ether40 ,a field of energy is intelligible4 ,it takes the place of the conception of action at a distance and of the ether4 ,no 8ether0 need be postulated as the carrier of the field energy in space4 ,it is its own carrier4 8,energy is the only real existing entity1 the primary conception1 which exists for us because our senses respond to it0 7,steinmetz74 8,lines of force10 says ,dr4 ,n4 ,r4 ,campbell1 the famous ,english physicist1 8are just lines of force1 independent for their existence of all surrounding bodies1 and there is no more to be said about them4444 ,our ,electrical theory1 so far from providing additional support for the conception of the ether filling all space1 does not require such a conception at all40 ,dr4 ,le ,bon finds the exhaustless source of electricity in the interior of atoms4 ,the atoms in one pound of earth contain enough energy to run all the factories1 mills1 railroads1 etc41 and light all the cities and villages of the ,united ,states1 for a month1 ,steinmetz tells us4 8,it would10 he states further 78,relativity and ,space10 ,page #de71 8supply the fuel for the biggest transatlantic liner for #cjj trips from ,america to ,europe and back4 ,and if this energy of one pound of dirt could be let loose instantaneously1 it would be equal in destructive powers to over a million tons of dynamite40 ,from the above statement1 we may well understand ,dr4 ,le ,bon's interpretation of the work of a dynamo3 8,matter being easily dissociated and constituting an immense reservoir of intra-atomic energy1 it is enough to admit that the lines of force seized upon by the conducting body 7the coils71 which cuts them and causes them to flow in the form of an electric current1 are constantly replaced at the expense of the intra-atomic energy4 ,this latter being relatively almost inexhaustible1 a single magnet can furnish an almost infinite number of lines of force40 ,it can be shown that the kinetic energy of one kilogram 7#b4b pounds7 weight of matter is about #ijjj millions of millions of kilogram-meters1 or #be thousand million kilowatt-hours 7a kilowatt-hour #ajjj watt hours74 ,this means1 in other words1 that the quantity of energy in the atoms of #b4b pounds of ordinary matter is thousands of million times greater than the energy of an equal quantity of coal1 released by chemical combustion4 ,estimating the total energy consumed during the year on earth for heat1 light1 power1 etc41 as about #ae millions of millions 7 #ae1jjj1jjj1jjj1jjj7 of kilowatt-hours1 ,steinmetz tells us that #fjj kilograms1 or less than two-thirds of a ton1 of 8dirt10 if it could be disintegrated into energy1 would supply all the heat1 light and energy demand of the whole earth for a year4 ,several eminent physicists are now specializing on the problem of how to liberate and control intra-atomic energy for man's uses--or abuses4 ,bearing in mind the present intellectual1 moral and economic status of our 8leaders of thought0 and their followers1 and remembering that one pound of common soil contains intra-atomic energy equal in destructive power to more than a million tons of dynamite1 let us hope that the secret of releasing and 8controlling0 intra-atomic energy will not be discovered in our day and age4 ,,chapter #f ,,proof ,,that ,,electrons ,,are ,,atoms ,,of ,,electricity ,,the ,,zeeman ,,effect ,heinrich ,hertz demonstrated in #ahhg that he could produce in the 8ether0--or at least in space--what are now known as 8wireless waves10 by allowing a charge of electricity to oscillate to and fro4 ,larmor and ,lorentz were1 at the same time1 endeavoring to formulate a theory which would account for the production of the far shorter light-waves4 ,lorentz supposed that each atom contained one or more infinitesimal particles1 or electric charges 7electrons71 whose excessively rapid vibrations caused the emission of light-rays4 ,maxwell showed that there must be a close connection between light and electricity1 a theory converted into demonstrable fact by the work of ,hertz4 ,that there is a similar relation between light and magnetism was the firm conviction of ,faraday4 ,in #ahde1 he placed a block of very dense glass between the poles of the most powerful electromagnet produceable at the time4 ,before turning on the switch1 he allowed a beam of light to pass through the glass1 producing 8polarization0--a modification of light-rays resulting from their reflection 7in this case from a crystalline substance71 imparting to the beam a definite direction--the plane of vibration or plane of polarization4 ,when the switch was closed1 permitting the flow of the electric current1 which produced the magnetic field1 the beam of light was 8rotated40 ,that is1 the beam of light was 8plane-polarized0 by the crystal1 and 8rotated0 by the magnetic field2 i4 e41 now changed into two 8circularly polarized0 rays1 one a left-handed motion and the other a right-handed motion 7in the direction of the hands of a watch74 ,this could be accounted for only on the theory that light is affected by magnetism1 since the beam was not rotated by the glass alone--in itself a very important discovery4 ,but the experiment did not yield ,faraday an answer to the question uppermost in his mind3 namely1 can a magnetic field change the rate of vibration of a light-emitting particle8 ,that is to say1 in effect1 can a magnetic field cause a ray of light to shift its normal place in the spectrum8 ,it was not until #ahfb1 seventeen years after the experiment just described1 that ,faraday attempted to solve this important theoretical problem4 ,he now placed a sodium flame in front of the slit of the spectroscope1 which normally yields two characteristic yellow lines 7the ,d lines of the spectrum71 and observed them with the best spectroscope at his command1 under the most powerful electromagnetic field which he could produce4 ,no change from the normal could be detected4 ,other observers tried the same experiment1 but with negative results4 ,we know that his theory was well founded1 and that only the lack of a better spectroscope and a more powerful magnet prevented his discovery of what is now known as the ,zeeman effect--a discovery which has already thrown a flood of light on a number of difficult physical problems4#bc ,working with much more powerful apparatus1 but following the same method of procedure employed by the immortal ,faraday1 ,dr4 ,pieter ,zeeman1 of ,leyden1 succeeded1 in #ahif1 in experimentally demonstrating the close relationship between light and magnetism4 ,dr4 ,h4 ,a4 ,lorentz1 then ,professor of ,physics in the ,university of ,leyden1 now mathematical physicist at the ,norman ,bridge ,laboratory of ,physics1 ,pasadena1 ,california1 had predicted the nature of the change in the spectral lines to be expected1 and this knowledge was used by ,dr4 ,zeeman as a check on his results4 ,using a ,rowland grating1 instead of a less efficient prism spectroscope1 ,dr4 ,zeeman found that when a relatively weak electric current was applied1 the two sodium lines were merely widened4 ,in a still more powerful magnetic field1 each of the lines was decomposed into two or three components1 when the lines of force were parallel to the line of sight4#bd ,moreover1 the rays of the components of each line 8were not those of natural light10 but were 8polarized in a characteristic way10 i4 e41 were circularly polarized in opposite directions--8the direction of the vibration depending in a simple manner on the direction of the magnetic lines of force40#be ,the same effect has more recently been produced in the case of the spectral rays of nearly--if not quite--all the other elements4 ,the process1 as described by ,dr4 ,george ,ellery ,hale1 is very simple3 8,we place our iron ore or spark between the poles of a powerful magnet1 and photograph its spectrum4 ,the lines behave in the most diverse way1 some splitting into triplets1 others into quadruplets1 quintuplets1 sextuplets1 etc4 ,one chromium line is resolved by the magnet into twenty-one components4444 ,the distance between the components of a line is directly proportional to the strength of the magnetic field40#bf ,the meaning of this splitting and polarization of light-rays in the magnetic field is that1 as ,lorentz had predicted1 there are present in the luminous vapor vibrating particles negatively charged1 or 8electrons40 ,measurement of the distances apart of the components of the triple line reveals the relation between the charge and the mass of the particles4#bg ,it is interesting to add that the disturbances in the magnetic field1 as observed by ,zeeman1 were precisely of the amount calculated by ,lorentz purely on theoretical grounds1 and the mass of the electron was found by this method to be #a_/ahdj that of the hydrogen atom4 ,by a different method1 ,sir ,j4 ,j4 ,thomson obtained a value of #a_/ahjj the mass of the hydrogen atom2 while ,dr4 ,robert ,a4 ,millikan1 by means of his famous 8electrical balance10 derived a value of #a_/ahde that of the hydrogen atom4#bh ,in his monograph of #aiac1 ,zeeman remarked that in discoveries of optics 8we may always cherish the hope that they will lead ultimately to applications to astronomy40 ,so far as study of solar phenomena and the ,zeeman effect are concerned1 this hope has been fully realized1 and attempts are being made to extend the applications of this method of investigation to other stellar bodies4 ,of the general value of ,zeeman's discovery1 ,dr4 ,hale writes3 8,the complex phenomena of the ,zeeman effect 7as revealed in a comparative study1 with powerful spectrographs1 and an intense magnetic field1 of the lines of a long list of elements7 furnish material available for wide generalization1 important in their bearing on theories of radiation and atomic structure0 7,op4 cit41 ,page #cf74 ,discovery by ,hale and his co-workers at ,mount ,wilson of the ,zeeman effect in sun-spots led to the very important conclusion that these disturbances represent whirling vortices of electrons1 producing a magnetic field4 8,the strength of the magnetic field produced1 which is measured by the degree of separation of the triple lines1 increases with the diameter of the spot4444 ,it has long been known that sun-spots usually occur in pairs1 and our study of the ,zeeman effect indicates that the two principal spots in such a group are almost invariably of opposite polarity0 7,hale1 ,op4 cit41 ,pages #bh-ca74 ,the sun1 like the earth is now known to be a magnet1 whose general magnetic field is about #hj times as intense as that of the earth4 ,at the distance of the earth the solar magnetic field is not appreciable1 8since the effect of one pole counteracts the equal and opposite effect of the other pole40 ,were it not for our knowledge concerning the ,zeeman effect1 it would not yet be known for a certainty that the sun is a vast magnetic globe1 since this fact could not be assumed to be a source of the sun's gravitational power4 8,indeed10 says ,dr4 ,hale1#bi 8its attraction cannot be felt by the most delicate instruments at the distance of the earth1 and would still be unknown were it not for the influence of magnetism on light4 ,auroras1 magnetic storms1 and such electric currents as those that recently deranged several ,atlantic cables are due1 not to the magnetism of the sun or its spots1 but probably to streams of electrons1 shot out from highly disturbed areas of the solar surface surrounding great sun-spots1 traversing #ic million miles of the ether of space1 and penetrating deep into the earth's atmosphere40 ,by means of the famous #aej-;foot tower telescope at ,mount ,wilson1 which produces at a fixed point in a laboratory an image of the sun about sixteen inches in diameter1 the magnetic phenomena of sun-spots are being studied to great advantage1 the enlarged sun-spots making possible separate observation of their various parts4 8,this analysis is accomplished with a spectroscope #hj feet in length1 mounted in a subterranean chamber beneath the tower40 ,by this means the very important discovery was made by ,director ,hale that the entire sun1 rotating on its axis1 is a great magnet4 8,hence10 says ,dr4 ,hale1 8we may reasonably infer that every star1 and probably every planet1 is also a magnet1 as the earth has been known to be since the days of ,gilbert's #8,de ,magnete4' ,barnett has succeeded in producing magnetism by rapidly whirling masses of metal in the laboratory0 7,hale1 8,the ,new ,heavens10 ,pages #fi-gj74 ,more recently 7,october1 #aibb71 ,hale1 ,ellerman and ,nicholson1 all of the ,mount ,wilson ,observatory1 have detected invisible sun-spots by searching for evidences of the ,zeeman effect in promising regions1 such as areas of flocculi following a large spot4 8,a special polarizing apparatus permits very small magnetic fields to be found by the alternate widening to red and violet of the iron triplet ,lambda #fagc10 say ,hale and ,adams 78,summary of the ,year's ,work at ,mount ,wilson10 ,publications of the ,astronomical ,society of the ,pacific1 ,october1 #aibb1 ,pages #bfi-gj ,vol4 ,,xxxiv1 ,no4 #bja74 8,the results confirm the view that a spot represents a vortex1 which becomes visible only when the cooling due to the expansion 7of gases7 is sufficiently great to produce a perceptible decrease in the brightness of the photosphere40 ,from what has been said1 it is evident that ,dr4 ,zeeman's desire to see the results of his discovery applied to the study of astronomical problems has been fully realized4 ,,the ,,stark ,,effect ,lorentz's prediction regarding the effect of a strong magnetic field on spectral rays1 and the movements of electrons in the field having been confirmed so brilliantly by ,zeeman1 it remained to ascertain what effect1 if any1 would be exerted by electrical force on light-rays4 ,the answer to this problem was given by ,prof4 ,johannes ,stark1 at ,aix-la-,chapelle1 in #aiac1 by his skillful demonstration of the electrical decomposition of the spectral rays of hydrogen1 helium and lithium4#cj ,stark's task was a more difficult one than ,zeeman's1 owing to the fact that he had to deal with luminescent gases1 which1 being conductors1 exhaust the electrical field almost before any observations can be made1 even hurriedly4 ,this condition gives rise to difficulties in connection with the application of the electric field4 ,but these were very ingeniously met by employment of highly evacuated tubes and the light emitted by the 8canal rays0--positively charged particles similar to the alpha rays4#ca ,where the rays issue from the perforated electrode 7or 8canal071 the conduction of electricity is weak1 and ,stark was able to apply intense electric fields in a small space4 ,it was then found that the diffuse rays of the spectrum produced were strongly influenced1 while the 8sharp0 rays were less so4 ,the attentive reader will note that this result was in marked contrast with the magnetic decomposition produced in the ,zeeman experiment1 in which the rays did not differ one from another in respect to the degree of their decomposition4 ,in all the details there is a difference between the electric and magnetic decompositions1 and analogy existing only in this1 namely1 that in both cases polarized rays were obtained4 ,in both cases the results produced were due to disturbance of the motions of electrons1 giving rise to broadening1 displacement or other modifications of spectral laws4 ,both 8effects0 confirm the theoretical view of ,maxwell1 namely1 that light is an electromagnetic phenomenon4 ,faraday's famous question is thus more than answered in the affirmative3 not only is the rate of vibration of 8atoms0 7electrons7 changed by a magnetic field1 but also under the action of an electrostatic field1 producing decomposition of certain spectral lines1 which are usually polarized1 as in the ,zeeman effect4 ,as a result of his intensive investigations of the ,zeeman effect1 ,dr4 ,henri ,a4 ,deslandres1 ,director of the ,astrophysical ,observatory at ,meudon 7a southern suburb of ,paris71 proposed a new general formula which represents the series relationship of the component lines and heads of bands both for emission and absorption spectra4 ,according to his experimentally-derived law1 8the origin of these radiations may be found in the transverse and longitudinal vibrations of the atoms40 ,the lamented ,dr4 ,p4 ,s4 ,epstein1 a gifted pupil of ,sommerfeld1 who--like ,mosely--fell a martyr to the ,world ,war1 succeeded in applying the quantum dynamics to the ,stark effect1 whereby the motions of the electron in producing the ,h-beta 7in the blue-green7 and ,h-gamma 7in the violet7 lines observed1 8are accounted for with great accuracy0 7,loring1 8,atomic ,theories10 ,page #fg74 ,it may be said in conclusion1 that the most promising attempts fully to explain the phenomena of the ,zeeman and ,stark effects seem to be made from the point of view of ,planck's ,quantum ,theory of ,light4 ,on the other hand1 it must be admitted that there has not been1 so far as ,i can ascertain1 any theory proposed which explains all of the phenomena involved4 ,,footnotes3 #bc ,for a good summary of the main results concerning the ,zeeman effect1 see von ,auerbach1 ,felix1 8,moderne ,magnetik10 ,leipsic1 #aiba4 ,an excellent account of the quantum treatment of the ,zeeman effect may be found in ,chapter ,,xv 7,series ,spectra7 of ,dr4 ,n4 ,r4 ,campbell's 8,modern ,electrical ,theory1 ,supplementary ,chapters10 ,cambridge ,university ,press1 #aiba4 #bd ,it seems that this phenomenon had previously been observed by ,m4 ,fievez4 7,cf4 ,michelson1 ,dr4 ,albert ,a41 8,light ,waves and ,their ,uses10 ,page #ajg47 8,he thought that each separate line was doubled or quadrupled40 ,lockyer1 in #ahff1 observed that some of the lines in a sun spot spectrum were widened4 ,prof4 ,charles ,young and ,w4 ,m4 ,mitchell observed that some of the lines were even double1 but it was not suspected that these phenomena were caused by a strong magnetic field in sun-spots1 brought about by free electrons being driven around in a vortex movement4 ,in fact1 ,mitchell referred to the doublets as 8reversals40 #be ,zeeman1 8,les ,lignes ,spectrales et les ,theories ,modernes10 ,scientia1 ,january #a1 #aiba1 ,page #ah 7,vol4 ,,xix1 ,no4 ,,cv--,i74 #bf ,hale1 8,ten ,years ,work of a ,mountain ,observatory10 ,pages #bi-cj1 ,washington1 ,d4 ,c4 7,carnegie ,institution of ,washington71 #aiae4 ,see also1 ,babcock1 ,harold ,d41 8,the ,zeeman ,effect for ,chromium10 ,contributions from ,mount ,wilson ,observatory1 ,vol4 ,,ii1 ,paper ,no4 #eb2 also 8,the ,correspondence between ,zeeman ,effect and ,pressure ,displacement for the ,spectra of ,iron1 ,chromium and ,titanium10 ,arthur ,s4 ,king1 ,loc4 cit41 ,paper ,no4 #df2 and 8,the ,zeeman ,effect on the ,sun10 ,adriaan van ,maanen1 ,publications of the ,astronomical society of the ,pacific1 ,page #bd1 ,vol4 ,,xxxiv1 ,no4 #aig 7,february1 #aibb74 #bg ,zeeman1 ,loc4 cit41 ,page #ah4 ,see also the classical monograph by the same author1 8,researches in ,magneto-,optics10 ,london1 #aiac4 #bh ,millikan1 ,physical ,review1 #b1 #adc 7#aiac72 8,the ,electron10 #aiag 7revised edition1 #aibd74 ,see also1 ,proceedings of the ,national ,academy of ,sciences1 #c1 #cad 7#aiag74 #bi 8,the ,new ,heavens10 ,page #gj1 ,new ,york1 #aibb4 #cj ,cf4 ,stark1 8,die ,atomionen chemischere ,elemente und ihre ,kanastrahlenspektra10 ,berlin1 #aiac4 ,see also1 8,elektrische ,spektralanalyse chemischen ,atome10 ,leipsic1 #aiad4 #ca ,called 8canal rays0 by the ,german physicist1 ,eugen ,goldstein1 who1 in #ahhf1 first obtained them by the use of a perforated cathode2 that is1 he used a metallic tube for a cathode1 through which tube1 called by ,goldstein a 8canal10 the rays issued4 ,,chapter #g ,,the ,,discovery ,,of ,,wireless ,,telegraphy ,the experimental foundation for the discovery of wireless telegraphy was laid by the researches of ,faraday4#cb ,accepting ,faraday's physical views as a point of departure1 ,james ,clerk ,maxwell 7#ahca-ahgi71 ,professor of ,experimental ,physics in the ,university of ,cambridge1 began 7about #ahfj7 the development of his constructive speculations in electrical theory which culminated in the now universally accepted electromagnetic theory of light4#cc ,fourteen years after the publication of ,maxwell's classic treatise1 ,heinrich ,hertz 7#ahei-ahid7--;a brilliant pupil of ,helmholtz 7#ahba-ahid7--succeeded in producing electrical discharges from a ,leyden jar1 which oscillations in turn gave rise to electromagnetic waves of far greater length than any previously known4#cd ,hertz demonstrated also that the velocity of propagation of these waves was the same as that of light-waves--approximately #ahf1jjj miles a second1 equivalent to about seven times the circumference of the earth in one second4 ,it was shown that the only difference between the ,hertzian 78wireless07 waves1 for example1 and the light-waves1 is in their respective length1 or1 reciprocally1 their rates of vibration per second4 ,hertz later demonstrated that these invisible waves produced by a ,leyden jar could be reflected1 refracted1 and polarized1 as in the case with the far shorter light-waves or rays4#ce ,these results had been predicted by ,maxwell4 ,in this great discovery the foundation for wireless telegraphy and wireless telephony was laid--for ,hertz had found what are now known as 8wireless0 or radio waves--destined1 perhaps1 to revolutionize our methods of obtaining power for machinery1 and for transportation1 as they have already revolutionized our methods of communication4 ,hertz had done more than this3 for his investigations made possible a far more satisfactory research into the structure of atoms4 8,if we were asked to pick out one date that stands out more prominently than others in our acquisition of knowledge bearing upon the structure of matter10 says ,dr4 ,albert ,c4 ,crehore1 8it might be this epoch-making work of ,hertz40#cf ,while it is true that the waves that ,hertz discovered and measured 8differ from light-waves merely in wave-length or period of vibration and quality10 on the other hand the difference in wave-length is so great that no instrument had as yet been devised to measure or detect waves that were meters long1 as compared with light-waves but a minute fraction of a centimeter in length4 ,it was ,hertz's task--following up ,maxwell's prediction--to devise an instrument which would detect waves not cognizable by our senses alone4 ,for this purpose he used a simple loop of wire with the ends brought near together1 each terminating in a metal ball4 ,when these balls were brought almost into contact1 a small electrical spark was seen to pass between the balls when the 8oscillator0--the apparatus used to generate the oscillating currents1 or electric waves1 of high frequency--was set in operation4#cg ,hertz not only proved that the speed of electric waves is the same as that of light1 and that they are subject1 under certain conditions1 to 8interference0 as are light-waves1 but he also succeeded in actually measuring the length of the waves produced by his crude apparatus4 ,this was accomplished by producing what are known as 8standing waves10 analogous to the sound-waves produced by an organ-pipe4 ,moving his detector slowly along the wire1 ,hertz observed that the spark would appear when a certain interval of space was reached1 and as he continued to move the detector the sparks would disappear and reappear at regular distances4 ,he rightly concluded that these points of disappearance and reappearance of the spark corresponded to the nodes and loops of the 8standing waves10 representing the wave-length of the electrical undulations4 ,it has since been established that the difference in wave-length between the electric undulations produced by ,hertz and those of light-waves may be enormous or quite moderate4 ,professor ,michelson tells us that 8a telegraphic wave01 which is practically an electromagnetic disturbance1 may be as long as #ajjj miles4 ,the waves produced by the oscillations of a condenser1 like a ,lyden jar1 may be as short as #ajj feet2 the waves produced by a ,hertz oscillator may be as short as one-tenth of an inch4 ,between this and the longest light-wave there is not an enormous gap1 for the latter has a length of about #a_/ajjj inch4 ,thus the difference between the ,hertz vibrations and the longest light-wave is less than the difference between the longest and shortest light-waves1 for some of the shortest oscillations are only a few millionths of an inch long4 ,doubtless even this gap will soon be bridged over4#ch ,the ,hertz apparatus was greatly improved by ,auguste ,righi1 in the ,university of ,bologna4 ,in the same class in physics was ,marconi1 who began his fruitful experiments in #ahie1 one year after ,sir ,oliver ,lodge had perfected the coherer4 ,lodge's coherer1 used by ,marconi in his early work1 consisted of a glass tube containing a pinch of nickel and silver filings in equal parts4 ,crude as this detector was1 judged by present-day standards1 it materially improved the conductivity of contact metals in the case of ,hertzian waves4 ,in #ahii wireless communication was established across the ,english ,channel1 and in #aijb ,marconi sent the first wireless message from ,england to ,america4 ,today1 wireless waves measuring miles from crest to crest are being employed in the transmission of messages from points separated by thousands of miles1 and the human voice has already been carried across the ,atlantic by radiophone1 but only in one direction4 ,the wireless sending and receiving station of the ,dutch government1 at ,kootmyck1 in the ,province of ,gelderland1 is equipped to employ a #ab1jjj-meter wave-length in sending and receiving simultaneously messages between ,holland and ,java1 #g1ejj miles distant4 ,it has the same capacity as our ,long ,island 7,rocky ,point7 station1 and is therefore one of the biggest in the world4 ,on ,december #ai1 #aibb1 a long distance phonograph which records sounds made hundreds of miles away was demonstrated to the ,society of ,western ,engineers1 by ,e4 ,h4 ,colpitts1 of the ,western ,electric ,company4 ,the transmission of electric power by radio is as yet but a dream2 but it is a dream which may come true within the next five years4#ci ,signals are now being received from stations situated at distances as great as #ab1jjj miles1 made possible1 it is believed by the existence of an electrical conducting layer--electrified dust expelled by the sun--some #aej miles in depth1 the bending of the radio-waves around the earth being caused by diffraction4 ,some unknown factor is operating to give the signals a strength millions of times greater than can be accounted for at present by any plausible theory1 according to ,prof4 ,j4 ,a4 ,fleming 7,fifth ,henry ,truman ,wood ,lecture before the ,royal ,society of ,arts1 ,london1 #aibb74 ,it is not reasonable to assume that no other electromagnetic waves remain to be discovered4 ,we may yet hear 8the roar of the sun-spots10 though ,edison's experiments along this line were unsuccessful4 ,what1 indeed1 were the mysterious 8signals0 occasionally reported as having been received at ,marconi wireless stations--registered1 it was reported in the press1 8only when a minimum of sixty-five-mile wave-lengths had been established10 but waves issuing from the mighty sun1 #ic1jjj1jjj miles distant8 ,however1 ,marconi tells us that one of the 8signals0 comes as three short raps--8,s0 in the ,morse code4 ,he believes that these 8signals0 may have been sent out from ,mars or ,venus4 ,similar mysterious 8signals0 were reported by wireless stations in different parts of the world during the apposition of ,mars in ,august1 #aibd4 8,outside of the radio-waves that are floating about there may be hundreds of others which we have not as yet been able to register4444 ,there may be many other waves coming to us from the sun1 of which we have no knowledge today4444 ,the human ear cannot hear below eight vibrations per second and not higher than about #cj1jjj vibrations per second4 ,certain animals can hear below and above that scale4 ,by means of our vacuum tubes certain researches indicate that a tremendous amount of noise goes on below the eight vibrations per second1 and still more noise above the #cj1jjj vibrations4 ,entirely new worlds lie in these two directions1 of which nothing is known today4 ,the vacuum tube is likely to solve these mysteries and take us into the uncharted worlds1 far into the unknown1 within the next few years40#dj ,in ,march1 #aibb1 the late ,dr4 ,charles ,p4 ,steinmetz said that he considered well founded the supposition that performances of low-power radio sending apparatus in transmitting messages to surprising distances gave an indication that the radiations peculiar to wireless transmission pass with equal ease through the earth or through the 8ether40 ,such radiations would be in accordance with accepted electrical laws1 as the ground1 to which both the sending antennae and the receiving set are connected1 would act as a return circuit for the current4 ,similarly1 water might serve as a medium for radio conversations between ships1 or between ships and the land4 ,moreover1 it was announced during the same month that wireless telephony had been revolutionized by the successful performances of the duplex transmitters which the ,general ,electric ,company had just completed4 ,conversations were held between ,new ,york and passengers aboard the steamer 8,america10 which1 at the time1 was at a distance of #cfj miles from shore4 ,the three-electrode audion or vacuum tube was perfected in #aiab1 making radio-telephony possible4 ,in #aiba1 ,reginald ,a4 ,heising1 a young physicist working for a degree of ,master of ,science at the ,university of ,wisconsin1 conceived the brilliant idea of putting into the vacuum tube the amount of energy produced by the voice1 and then getting it out many times amplified in the form of high-frequency power in the antenna4 ,this problem he soon solved1 so far as the principle of the modulation system was concerned1 and in #aibb the practical problem was worked out and the method all but perfected4 ,all these great utilitarian advances have been made possible by the researches of men interested in the advancement of knowledge for its own sake4 ,as has been pointed out recently by ,dr4 ,hale 78,the ,new ,heavens10 ,pages #hg-hh71 8,faraday1 studying the laws of electricity1 discovered the principles which rendered the dynamo possible4 ,maxwell1 ,henry and ,hertz1 equally unconcerned with material advantage1 made wireless telegraphy possible4444 ,wireless telephony and transcontinental telephony without wires were both rendered possible by studies of the nature of the electric discharge in vacuum tubes40 ,in an interview in ,december1 #aibb1 ,dr4 ,nikola ,tesla gave it as his opinion1 based upon experiments already carried out in his own laboratory in ,new ,york ,city1 that power flashed through space by radio will soon be employed in all the world's activities4 8,besides bridging enormous distances in flight and wireless conversation10 he said1 8modern science will span the earth with power flashed through the air by radio4 ,airplanes and ships and trains will carry no fuel1 but will run by transmitted energy4 ,with wireless power no one--explorers1 travelers1 campers--need be cut off from civilization and its comforts40 8,not only that1 but we shall see at great distances by aid of wireless energy4 ,and seeing our neighbors across the oceans will make for a united social and political world40 ,,footnotes3 #cb ,see his 8,experimental ,researches in ,electricity10 ,everyman's ,library ,series4 #cc ,maxwell1 ,james ,clerk1 8,treatise on ,electricity and ,magnetism10 #ahgc4 #cd ,the theoretical investigation of the mode of discharge of a condenser had been given by ,sir ,william ,thomson 7later ,lord ,kelvin7 in #ahec1 in the ,philosophical ,magazine for ,june of that year4 #ce ,when all the atoms and molecules of a substance vibrate in one plane1 e4 g41 as the plane of a train of waves would be if drawn on this page1 the wave is said to be polarized4 ,ordinarily1 light-rays are sent out from particles vibrating in different planes2 they may be vertical or horizontal1 or diagonal1 or they may move in a curved path--circles or ellipses4 ,ordinary light-vibrations are mixed up together1 vibrating in all planes1 and special devices--8polarizers0--are required in order to separate any one particular vibration from the rest4 #cf ,crehore1 ,dr4 ,albert ,c41 8,the ,mystery of ,matter and ,energy10 ,page #bh1 ,new ,york1 #aiag4 #cg ,by means of an induction coil coupled to a circuit containing capacity terminals1 thus forming an 8oscillatory circuit40 #ch ,michelson1 ,dr4 ,a4 ,a41 8,light ,waves and ,their ,uses10 ,pages #afj-fa4 ,the gap was closed during the year #aibd1 heat-waves being measured which were of such great length as to merge into the shortest ,hertzian or 8wireless0 waves4 #ci ,see an interesting article on this question in ,science and ,invention1 ,december1 #aibb1 ,page #gdd 7,vol4 ,x1 ,whole ,no4 #aaf74 #dj ,gernback1 ,h41 ,editorial in ,science and ,invention1 ,december1 #aibb4 ,transcriber's ,notes pg #bd ,changed3 conducting plate in the neighborhod of a magnet to3 conducting plate in the neighborhood of a magnet pg #be ,changed3 was affected by on ordinary magnet to3 was affected by an ordinary magnet