CHAPTER III.

SCIENTIFIC RESEARCHES: FIRST PERIOD.

From first to last the original scientific researches of Faraday extend over a period of forty-four years, beginning with an analysis of caustic lime, published in the _Quarterly Journal of Science_ in 1816, and ending with his last unfinished researches of 1860 to 1862, on the possible existence of new relations between magnetism and gravity and between magnetism and light. The mere list of their titles fills several pages in the catalogue of scientific papers published by the Royal Society.

For convenience of description, these forty-four years may be divided into three periods: the first lasting from 1816 to 1830, a period of miscellaneous and in some respects preliminary activity; the second from 1831 to the end of 1839, the period of the classical experimental researches in electricity down to the time when they were temporarily suspended by the serious state of his health; the third from 1844, when he was able to resume work, down to 1860, a period which includes the completion of the experimental researches on electricity, the discovery of the relations between light and magnetism, and that of diamagnetism.

[Sidenote: RESEARCHES BEGINNING.]

Faraday’s first research was an analysis for Sir Humphry Davy of a specimen of caustic lime which had been sent to him by the Duchess of Montrose from Tuscany. The _Quarterly Journal of Science_, in which it appeared, was a precursor of the _Proceedings of the Royal Institution_, and was indeed edited by Professor W. F. Brande. Faraday frequently wrote for it during these years, and took editorial charge of it on more than one occasion during Brande’s holidays. The paper on caustic lime was reprinted by Faraday in the volume of his “Experimental Researches on Chemistry and Physics,” prefaced by the following note:--

I reprint this paper at full length; it was the beginning of my communications to the public, and in its results very important to me. Sir Humphry Davy gave me the analysis to make as a first attempt in chemistry, at a time when my fear was greater than my confidence, and both far greater than my knowledge; at a time also when I had no thought of ever writing an original paper on science. The addition of his own comments, and the publication of the paper, encouraged me to go on making, from time to time, other slight communications, some of which appear in this volume. Their transference from the _Quarterly_ into other journals increased my boldness, and now that forty years have elapsed, and I can look back on what successive communications have led to, I still hope, much as their character has changed, that I have not either now or forty years ago been too bold.

For the next two or three years Faraday was very closely occupied in the duties of assisting Sir Humphry Davy in his researches, and in helping to prepare the lectures for both Davy and Brande. Yet he found time still to work on his own account. In 1817 he had six papers and notes in the _Quarterly Journal of Science_, including one on the escape of gases through capillary tubes, and others on wire-gauze safety lamps and Davy’s experiments on flame. In 1818 he had eleven papers in the _Journal_; the most important being on the production of sound in tubes by flames, while another was on the combustion of the diamond. In 1819 he had nineteen papers in the _Quarterly Journal_, chiefly of a chemical nature. These related to boracic acid, the composition of steels, the separation of manganese from iron, and on the supposed new metal, “Sirium” or “Vestium,” which he showed to be only a mixture of iron and sulphur with nickel, cobalt, and other metals.

[Sidenote: OERSTED’S DISCOVERY.]

The year 1820 was marked in the annals of science by the discovery, by Oersted of Copenhagen, of the prime fact of electromagnetism, the deflexion which is produced upon a magnetic needle by an electric current that passes either under or over the needle. Often had it been suspected that there must be some connection between the phenomena of electricity and those of magnetism. The similarities between the attractions and repulsions caused by electrified bodies, and those due to the magnet when acting on iron, had constantly suggested the possibility that there was some real connection. But, as had been pointed out centuries before by St. Augustine, while the rubbed amber will attract any substance if only small or light enough, being indifferent to its material, the magnet will only attract iron or compounds of iron, and is totally inoperative[16] on all other substances. Again, while it had been noticed that in houses which had been struck by lightning knives, needles, and other steel objects near the path of the electric flash had become magnetised, no one had been able, by using the most powerful electric machines, to repeat with certainty the magnetisation of needles. In vain they had tried to magnetise knives and wires by sending sparks through them. Sometimes they showed a trace of magnetism, sometimes none. And in the cases where some slight magnetisation resulted, the polarity could not be depended upon. Van Swinden had written a whole treatise in two volumes on the analogies between electricity and magnetism, but left the real relation between the two more obscure than ever. After the invention, in 1800, of the voltaic pile, which for the first time provided a means of generating a steady flow or current of electricity, several experimenters, including Oersted himself, had again essayed to discover the long-suspected connection, but without success. Oersted was notoriously a poor experimenter, though a man of great philosophical genius. Having in 1820 a more powerful voltaic battery in operation than previously, he repeated[17] the operation of bringing near to the compass needle the copper wire that conveyed the current; and, laying it parallel to the needle’s direction, and over or under it, found that the needle tended to turn into a direction at right angles to the line of the current, the sense of the deviation depending upon the direction of flow of the current, and also on the position of the wire as to whether it were above or below the needle. A current flowing from south to north over the needle caused the north-pointing end of the needle to be deflected westwards. If the wire were vertical, so that the current flowed downwards, and a compass needle was brought near the wire on the south side, therefore tending under the earth’s directive influence to point northwards toward the wire, it was observed that the effect of the current flowing in the wire was to cause the north-pointing end of the needle to turn westwards. Or, reversing the flow of current, the effect on the needle was reversed; it now tended eastwards. All these things Oersted summed up in the phrase that “the electric conflict acts in a revolving manner” around the wire.[18] In modern phraseology the whole of the actions are explained if one can conceive that the effect of the electric flow in the wire is to tend to make the north pole of a magnet revolve in one sense around the wire, whilst it also tends to make the south pole of the magnet revolve around the wire in the other sense. The nett result in most cases is that the magnetic needle tends to set itself square across the line of the current. Oersted himself was not too clear in his explanations, and seems, in his later papers, to have lost sight of the circular motion amidst repulsions and attractions.

This discovery, which showed what was the geometrical relation between the magnet and the current, also showed why the earlier attempts had failed. It was requisite that the electricity should be in a state of steady flow; neither at rest as in the experiments with electric charges, nor yet in capricious or oscillatory rush as in those with spark-discharges. Faraday, adverting a quarter of a century later to Oersted’s discovery, said: “It burst open the gates of a domain in science, dark till then, and filled it with a flood of light.”

The very day that Oersted’s memoir was published in England, Davy brought a copy down into the laboratory of the Royal Institution, and he and Faraday at once set to work to repeat the experiments and verify the facts.

It is a matter of history how, on the publication of Oersted’s discovery, Ampère leaped forward to generalise on electromagnetic actions, and discovered the mutual actions that may exist between two currents, or rather between two conducting wires that carry currents. They are found to experience mutual mechanical forces urging them into parallel proximity. Biot and Laplace added to these investigations, as also did Arago. Davy discovered that the naked copper wire, while carrying a current, could attract iron filings to itself--not end-ways in adherent tufts, as the pole of a magnet does, but laterally, each filing or chainlet of filings tending to set itself tangentially at right angles to the axis of the wire.

[Sidenote: A PARADOXICAL PHENOMENON.]

This curious right-angled relation between electric flow and magnetic force came as a complete paradox or puzzle to the scientific world. It had taken centuries to throw off the strange unmechanical ideas of force which had dominated the older astronomy. The epicyclic motions of the planets postulated by the Ptolemaic system were in no way to be accounted for upon mechanical principles. Kepler’s laws of planetary motion were merely empirical, embodying the results of observation, until Newton’s discovery of the laws of circular motion and of the principle of universal gravitation placed the planetary theory on a rational basis. Newton’s laws required that forces should act in straight lines, and that to every action there should be an equal and opposite reaction. If A attracted B, then B attracted A with an equal force, and the mutual force must be in the line drawn from A to B. The discovery by Oersted that the magnet pole was urged by the electric wire in a direction _transverse_ to the line joining them, appeared at first sight to contravene the ideas of force so thoroughly established by Newton. How could this transversality be explained? Some sought to explain the effect by considering the conducting wire to operate as if made up of a number of short magnets set transversely across the wire, all their north poles being set towards the right, and all their south poles towards the left. Ampère took the alternative view that the magnet might be regarded as equivalent to a number of electric currents circulating transversely around the core as an axis. In neither case was the explanation complete.

[Sidenote: TWO YEARS WASTED.]

Faraday’s scientific activities in the year 1820 were very marked. New researches on steel had been going on for some months. It had been hoped that by alloying iron with some other metals, such as silver, platinum, or nickel, a non-rusting alloy might be found. This idea took its rise from the erroneous notion that meteoric iron, which is richly alloyed with nickel, does not rust. Faraday found nickel steel to be more readily oxidised, not less, than ordinary steel. The platinum steel was also a failure. Silver steel was of more interest, though it was found impossible to incorporate in the alloy more than a small percentage of silver. Nevertheless, silver steel was used for some time by a Sheffield firm for manufacture of fenders. The alloys of iron with platinum, iridium, and rhodium were also of no great use. But the research demonstrated the surprising effects which minute quantities of other metals may have upon the quality of steel. Occasionally in later life Faraday would present one of his friends with a razor made from his own special steel. A paper on the use of alloys of steel in surgical instrument making was published in the _Quarterly Journal_ in collaboration with Mr. Stodart. Faraday also read his first paper before the Royal Society on two new compounds of chlorine and carbon, and on a new compound of iodine, carbon, and hydrogen. He also succeeded in making artificial plumbago from charcoal. In writing to his friend Professor G. de la Rive, he gives a long and chatty abstract of his researches on the alloys of steel. They appear to have originated in some analyses of wootz or Indian steel, a material which, when etched with acid, shows a beautifully damascened or reticulated surface. This effect Faraday never found with pure steel, but imitated it successfully with a steel alloyed with “the metal of alumine,” an element which down to that time had not been isolated. He then describes the rhodium, silver, and nickel steels, and mentions incidentally how he has been surprised to discover that he can volatilise silver, and that he cannot reduce the metal titanium. He is doubtful whether this metal “ever has been reduced at all in the pure state.” [It can now be readily reduced either in the electric arc or by the use of metallic aluminium.] He winds up the letter with the words: “Pray pity us that, after two years’ experiments, we have got no further; but I am sure, if you knew the labour of the experiments, you would applaud us for our perseverance at least.”

In 1821, the year of his marriage, came the first of the important scientific discoveries which brought him international fame. This was the discovery of the electromagnetic rotations. It appears that Oersted’s brilliant flash of insight that the “electric conflict acts in a revolving manner” upon the pole of the neighbouring compass needle had been lost sight of in the discussions which followed, and to which allusion has been made above. All the world was thinking about attractions and repulsions. Two men, however, seem to have gone a little further in their ideas. Dr. Wollaston had suggested that there ought to be a tendency, when a magnet pole was presented towards a straight conducting wire carrying a current, for that conducting wire to revolve around its own axis. This effect--though in recent years it has been observed by Mr. George Gore--he unsuccessfully tried to observe by experiments. He came in April, 1821, to the laboratory of the Royal Institution to make an experiment, but without result. Faraday, at the request of his friend Phillips, who was editor of the _Annals of Philosophy_, wrote for that magazine in July, August, and September a historical sketch of electromagnetism down to date. This was one of the very few of Faraday’s writings that was anonymous. It was simply signed “M.” This is in vol. iii. p. 107. On p. 117 the editor says: “To the historical sketch of electromagnetism with which I have been favoured by my anonymous correspondent, I shall add a sketch of the discoveries that have been made by Mr. Faraday of the Royal Institution.” In the course of this work Faraday repeated for his own satisfaction almost all the experiments that he described. This led him to discover that a wire, included in the circuit, but mounted so as to hang with its lower end in a pool of quicksilver, could rotate around the pole of a magnet; and conversely that if the wire were fixed and the pole of the magnet free to move, the latter would rotate around the former. “I did not realise,” he wrote, “Dr. Wollaston’s expectation of the rotation of the electromagnetic wire around its axis.” As was so often his custom, he had no sooner finished the research for publication than he dashed off a brief summary of it in a letter to one of his friends. On this occasion it was Professor G. de la Rive, of Geneva, who was the recipient of his confidences. On September 12 he wrote:--

[Sidenote: LETTER TO DE LA RIVE.]

I am much flattered and encouraged to go on by your good opinion of what little things I have been able to do in science, and especially as regards the chlorides of carbon.

* * * * *

You partly reproach us here with not sufficiently esteeming Ampère’s experiments on electromagnetism. Allow me to extenuate your opinion a little on this point. With regard to the experiments, I hope and trust that due weight is allowed to them; but these you know are few, and theory makes up the great part of what M. Ampère has published, and theory in a great many points unsupported by experiments when they ought to have been adduced. At the same time, M. Ampère’s experiments are excellent, and his theory ingenious; and, for myself, I had thought very little about it before your letter came, simply because, being naturally sceptical on philosophical theories, I thought there was a great want of experimental evidence. Since then, however, I have engaged on the subject, and have a paper in our “Institution Journal,” which will appear in a week or two, and that will, as it contains experiment, be immediately applied by M. Ampère in support of his theory, much more decidedly than it is by myself. I intend to enclose a copy of it to you with the other, and only want the means of sending it.

I find all the usual attractions and repulsions of the magnetic needle by the conjunctive wire are deceptions, the motions being not attractions or repulsions, nor the result of any attractive or repulsive forces, but the result of a force in the wire, which instead of bringing the pole of the needle nearer to, or further from the wire, endeavours to make it move round it in a never ending circle and motion whilst the battery remains in action. I have succeeded not only in showing the existence of this motion theoretically, but experimentally, and have been able to make the wire revolve round a magnetic pole, or a magnetic pole round the wire, at pleasure. The law of revolution, and to which all the other motions of the needle and wire are reducible, is simple and beautiful.

Conceive a portion of connecting wire north and south, the north end being attached to the positive pole of a battery, the south to the negative. A north magnetic pole would then pass round it continually in the apparent direction of the sun, from east to west above, from west to east below.

Reverse the connections with the battery, and the motion of the pole is reversed; or if the south pole be made to revolve, the motions will be in the opposite directions, as with the north pole.

If the wire be made to revolve round the pole, the motions are according to those mentioned. In the apparatus I used there were but two plates, and the directions of the motions were of course[19] the reverse of those with a battery of several pairs of plates, and which are given above. Now I have been able, experimentally, to trace this motion into its various forms as exhibited by Ampère’s, Nelice’s, &c., and in all cases to show that the attractions and repulsions are only appearances due to this circulation of the pole, to show that dissimilar poles repel as well as attract, and that similar poles attract as well as repel, and to make, I think, the analogy between the helix and common bar magnet far stronger than before. But yet I am by no means decided that there are currents of electricity in the common magnet.

I have no doubt that electricity puts the circles of the helix into the same state as those circles are in, that may be conceived in the bar magnet, but I am not certain that this state is directly dependant on the electricity, or that it cannot be produced by other agencies; and therefore, until the presence of electrical currents be proved in the magnet by other than magnetical effects, I shall remain in doubt about Ampère’s theory.

* * * * *

Wishing you all health and happiness, and waiting for news from you,

I am, my dear Sir, your very obliged and grateful

M. FARADAY.

The reference at the beginning of this letter to the chlorides of carbon has to do with his discovery communicated to the Royal Society. Later in the year, a joint paper on another compound of carbon and chlorine, by himself and his friend Richard Phillips, was sent in. Both were printed together in the _Philosophical Transactions_ of 1821.

[Sidenote: LEAVES FROM THE NOTE-BOOK.]

The following is an extract from Faraday’s laboratory book relating to the discovery. The account is incomplete, a leaf having been torn out:--

1821, Sept. 3.

The effort of the wire is always to pass off at a right angle from the pole, indeed to go in a circle round it, so when either pole was brought up to the wire perpendicular to it and to the radius of the circle it described, there was neither attraction nor repulsion, but the moment the pole varied in the slightest manner either in or out, the wire moved one way or the other.

The poles of the magnet act on the bent wire in all positions and not in the direction _only_ of any axis of the magnet, so that the current can hardly be cylindrical or arranged round the axis of a cylinder?

From the motion above a north magnet pole in the centre of one of the circles should make the wire continually turn round. Arranged a magnet needle in a glass tube with mercury about it, and by a cork, water, &c., supported a connecting wire so that the upper end should go into the silver cup and its mercury, and the lower move in a channel of mercury round the pole of the needle. The battery arranged with the wire as before. In this way got the revolution of the wire round the pole of the magnet. The direction was as follow, looking from above down:--

Very satisfactory, but make more sensible apparatus.

Tuesday, Sept. 4.

Apparatus for revolution of wire and magnet. A deep basin with bit of wax at bottom and then filled with mercury. A magnet stuck upright in wax so that pole just above the surface of mercury. Then piece of wire floated by cork at lower end dipping into merc^y and above into silver cup as before:--

The research on the electromagnetic rotations, which was published in the _Quarterly Journal of Science_ for October, 1821 (and reprinted in the second volume of the “Experimental Researches in Electricity”), was the occasion of a very serious misunderstanding with Dr. Wollaston and his friends, which at one time threatened to cause Faraday’s exclusion from the Royal Society. Faraday’s prompt and frank action in appealing to Dr. Wollaston saved him in a very unpleasant crisis; and the latter came three or four times to the laboratory to witness the experiments. On Christmas Day of the same year, Faraday succeeded in making a wire through which an electric current is passing move under the influence of the earth’s magnetism alone. His brother-in-law, George Barnard, who was in the laboratory at the time, wrote:--“All at once he exclaimed, ‘Do you see, do you see, do you see, George?’ as the wire began to revolve. One end I recollect was in the cup of quicksilver, the other attached above to the centre. I shall never forget the enthusiasm expressed in his face and the sparkling in his eyes!”

[Sidenote: SCENES IN THE LABORATORY.]

In 1822 little was added to Faraday’s scientific work. He had a joint paper with Stodart on steel before the Royal Society, and in the _Quarterly Journal_ two short chemical papers and four on electromagnetical motions and magnetism. He had long kept a commonplace book in which he entered notes and queries as well as extracts from books and journals; but this year he began a fresh manuscript volume, into which he transferred many of the queries and suggestions of his own originating. This volume he called “Chemical Notes, Hints, Suggestions, and Objects of Pursuit.” It contains many of the germs of his own future discoveries, as the following examples show:--

Convert magnetism into electricity.

Do pith balls diverge by disturbance of electricities in consequence of induction or not?

General effects of compression, either in condensing gases, or producing solutions, or even giving combinations at low temperatures.

Light through gold leaf on to zine or most oxidable metals, these being poles--or on magnetic bars.

Transparency of metals. Sun’s light through gold leaf. Two gold leaves made poles--light passed through one to the other.

Whenever any query found an answer, he drew his pen through it and added the date. In front of the book--probably at some later time--he wrote these words:--

I already owe much to these notes, and think such a collection worth the making by every scientific man. I am sure none would think the trouble lost after a year’s experience.

A striking example had already occurred of similar suggestive notes in the optical queries of Sir Isaac Newton.

In another manuscript notebook occur the following entries under date of September 10, 1821:--

2 similar poles though they repell at most distances attract at very small distances and adhere. Query why....

Could not magnetise a plate of steel so as to resemble flat spiral. Either the magnetism would be very weak and irregular or there would be none at all.

These are interesting as showing how Faraday was educating himself by continual experiment. The explanation of each of these paradoxes has long passed into the commonplace of physics; but they would still puzzle many who have learned their science bookishly at second-hand.

It will be noted that amongst the entries cited above there are two of absolutely capital importance, one foreshadowing the great discovery of magneto-electric induction, the other indicating how the existence of electro-optical relations was shaping itself as a possibility in Faraday’s mind. An entry in his laboratory book of September 10 is of great interest:--

Polarised a ray of lamp-light by reflection, and endeavoured to ascertain whether any depolarising action [is] exerted on it by water placed between the poles of a voltaic battery in a glass cistern; one Wollaston’s trough used; the fluids decomposed were pure water, weak solution of sulphate of soda, and strong sulphuric acid: none of them had any effect on the polarised light, either when out of or in the voltaic circuit, so that no particular arrangement of particles could be ascertained in this way.

[Sidenote: AN UNSUCCESSFUL EXPERIMENT.]

It may be added that no such optical effect of electrolytic conduction as that here looked for has yet been discovered. The experiment, unsuccessful at that day, remains still an unsuccessful one. A singular interest attaches to it, however, and it was repeated several times by Faraday in subsequent years, in hope of some results.

In 1823 Faraday read two papers to the Royal Society, one on Liquid Chlorine, the other on the Condensation of several Gases into Liquids. No sooner was the work completed than he dashed off a letter to De la Rive to tell him what he had accomplished. Under date March 24, 1823, he writes:--

I have been at work lately, and obtained results which I hope you will approve of. I have been interrupted twice in the course of experiments by explosions, both in the course of eight days--one burnt my eyes, the other cut them; but fortunately escaped with slight injury only in both cases, and am now nearly well. During the winter I took the opportunity of examining the hydrate of chlorine, and analysing it; the results, which are not very important, will appear in the next number of the _Quarterly Journal_, over which I have no influence. Sir H. Davy, on seeing my paper, suggested to me to work with it under pressure, and see what would happen by heat, &c. Accordingly I enclosed it in a glass tube hermetically sealed, heated it, obtained a change in the substance, and a separation into two different fluids; and upon further examination I found that the chlorine and water had separated from each other, and the chlorine gas, not being able to escape, had condensed into the liquid form. To prove that it contained no water, I dried some chlorine gas, introduced it into a long tube, condensed it, and then cooled the tube, and again obtained fluid chlorine. Hence what is called chlorine gas is the vapour of a fluid....

* * * * *

I expect to be able to reduce many other gases to the liquid form, and promise myself the pleasure of writing you about them. I hope you will honour me with a letter soon.

I am, dear Sir, very faithfully, your obedient servant,

M. FARADAY.

[Sidenote: CHLORINE LIQUEFIED.]

The work of liquefying the gases had been taken up by Faraday during his hours of liberty from other duties. It was probably his characteristic dislike to “doubtful knowledge” which prompted him to re-examine a substance which had at one time been regarded as chlorine in a solid state, but which Davy in 1810 had demonstrated to be a hydrate of that element. The first work was, as narrated above, to make a new analysis of the supposed substance. This analysis, duly written out, was submitted to Sir Humphry, who, without stating precisely what results he anticipated might follow, suggested heating the hydrate under pressure in a hermetically sealed glass tube. This Faraday did. When so heated, the tube filled with a yellow atmosphere, and on cooling was found to contain two liquids, one limpid and colourless like water, the other of an oily appearance. Concerning this research a curious story is told in the life of Davy. Dr. Paris, Davy’s friend and biographer, happened to visit the laboratory while Faraday was at work on these tubes. Seeing the oily liquid, he ventured to rally the young assistant upon his carelessness in employing greasy tubes. Later in the day, Faraday, on filing off the end of the tube, was startled by finding the contents suddenly to explode; the oily matter completely disappearing. He speedily ascertained the cause. The gas, liberated from combination with water by heat, had under the pressure of its own evolution liquefied itself, only to re-expand with violence when the tube was opened. Early the next day Dr. Paris received the following laconic note:--

DEAR SIR,--

The _oil_ you noticed yesterday turns out to be liquid chlorine.

Yours faithfully, M. FARADAY.

Later he adopted a compressing syringe to condense the gas, and again succeeded in liquefying it. Davy, who added a characteristic note to Faraday’s published paper, immediately applied the same method of liquefaction by its own pressure to hydrochloric acid gas; and Faraday reduced a number of other gases by the same means. These researches were not without danger. In the preliminary experiments an explosion of one of the tubes drove thirteen fragments of glass into Faraday’s eye. At the end of the year he drew up a historical statement on the liquefaction of gases, which was published in the _Quarterly Journal_ for January, 1824. A further statement by him was published in the _Philosophical Magazine_ for 1836; and in 1844 his further researches on the liquefaction of gases were published in the _Philosophical Transactions_.

In 1824 Faraday again brought to the Royal Society a chemical discovery of first importance. The paper was on some new compounds of carbon and hydrogen, and on certain other products obtained during decomposition of oil by heat. From condensed oil-gas, so obtained, Faraday succeeded in separating the liquid known as benzin or benzol, or, as he named it at the time, bicarburet of hydrogen. It has since its discovery formed the basis of several great chemical industries, and is manufactured in vast quantities. Prior to the reading of this paper he had, as we have already related, been elected a Fellow of the Royal Society, an honour to which he had for some years aspired, and which stood alone in his regard above the scientific honours of later years.

In this year he tried, amongst his unsuccessful experiments, two of singular interest. One was an attempt to find whether two crystals (such as nitre) exercised upon one another any polar attractions like those of two lodestones. He suspended them by fibres of cocoon silk, and, finding this material not delicate enough, by spider-lines. The other was an attempt to discover magneto-electricity. For various reasons he concluded that the approximation of the pole of a powerful magnet to a conductor carrying a current would have the effect of diminishing the amount of that current. He placed magnets within a copper wire helix, and observed with a galvanometer whether the current sent through the circuit of the helix by a given battery was less when the magnet was absent. The result was negative.

[Sidenote: RESEARCH ON OPTICAL GLASS.]

In this year also began the laborious researches on optical glass, which though in themselves leading to no immediate success of commercial value, nevertheless furnished Faraday with the material essential at the time for the making of the most momentous of all his discoveries. A committee had been appointed by the President and Council of the Royal Society for the improvement of glass for optical purposes, and Faraday was amongst those chosen to act upon it.

In 1825 the Royal Society Committee delegated the investigation of optical glass to a sub-committee of three, Herschel (afterwards Sir John), Dollond (the optician), and Faraday. The chemical part, including the experimental manufacture, was entrusted to Faraday. Dollond was to work the glass and test its qualities from the instrument maker’s point of view, whilst Herschel was to examine its refraction, dispersion, and other physical properties. This sub-committee worked for nearly five years, though by the removal of Herschel from England its number was reduced to two. In 1827 the work became more arduous. Faraday thus writes:--

The President and Council of the Royal Society applied to the President and Managers of the Royal Institution for leave to erect on their premises an experimental room with a furnace, for the purpose of continuing the investigation on the manufacture of optical glass. They were guided in this by the desire which the Royal Institution has always evinced to assist in the advancement of science; and the readiness with which the application was granted showed that no mistaken notion had been formed in this respect. As a member of both bodies, I felt much anxiety that the investigation should be successful. A room and furnaces were built at the Royal Institution in September, 1827, and an assistant was engaged, Sergeant Anderson, of the Royal Artillery. He came on the 3rd of December.

Anderson, who was thus made assistant to Faraday, remained in that capacity till his death in 1866. He was a most devoted servant. In a footnote to the “Experimental Researches” (vol. iii. p. 3) Faraday in 1845 wrote of him:--

I cannot resist the occasion that is thus offered me of mentioning the name of Mr. Anderson, who came to me as an assistant in the glass experiments, and has remained ever since in the laboratory of the Royal Institution. He assisted me in all the researches into which I have entered since that time; and to his care, steadiness, exactitude, and faithfulness in the performance of all that has been committed to his charge, I am much indebted.--M. F.

Tyndall, who had a great admiration for Anderson, declared that his merits as an assistant might be summed up in one phrase--blind obedience. The story is told of him by Benjamin Abbott:--

[Sidenote: ANDERSON’S OBEDIENCE.]

Sergeant Anderson ... was chosen simply because of the habits of strict obedience his military training had given him. His duty was to keep the furnaces always at the same heat, and the water in the ashpit always at the same level. In the evening he was released, but one night Faraday forgot to tell Anderson he could go home, and early next morning he found his faithful servant still stoking the glowing furnace, as he had been doing all night long.

The research on optical glass was viewed askance by several parties. The expenditure of money which it involved was one of the “charges” hurled against the Council of the Royal Society by Sir James South in 1830. Nevertheless it was deemed sufficiently important to receive powerful support, as the following letter shows:--

Admiralty, 20 Dec., 1827.

SIR,

I hereby request, on behalf of the Board of Longitude, that you will continue, in the furnace built at the Royal Institution, the experiments on glass, directed by the joint Committee of the Royal Society and the Board of Longitude and already sanctioned by the Treasury and the Board of Excise.

I am, Sir, Your obedient servant, THOMAS YOUNG, M.D., Sec. Bd. Long.

Michael Faraday, Esq., Royal Institution.

In February, 1825, Faraday’s duties towards the Royal Institution were somewhat modified. Hitherto he had been nominally a mere assistant to Davy and Brande, though he had occasionally undertaken lectures for the latter. Now, on Davy’s recommendation, he was, as we have seen, appointed by the managers Director of the Laboratory under the superintendence of the Professor of Chemistry. He was relieved, “because of his occupation in research,” from his duty as chemical assistant at the lectures.

The research on optical glass was not concluded till 1829, when its results were communicated to the Royal Society in the Bakerian lecture of that year--a memoir so long that it is said three sittings were occupied in its delivery. It is printed _in extenso_ in the _Philosophical Transactions_ of 1830. It opens as follows:--

When the philosopher desires to apply glass in the construction of perfect instruments, and especially the achromatic telescope, its manufacture is found liable to imperfections so important and so difficult to avoid, that science is frequently stopped in her progress by them--a fact fully proved by the circumstance that Mr. Dollond, one of our first opticians, has not been able to obtain a disc of flint glass 4½ inches in diameter, fit for a telescope, within the last five years; or a similar disc, of 5 inches, within the last ten years.

This led to the appointment by Sir H. Davy of the Royal Society Committee, and the Government removed the excise restrictions, and undertook to bear all the expenses as long as the investigation offered a reasonable hope of success.

The experiments were begun at the Falcon Glass Works, three miles from the Royal Institution, and continued there in 1825, 1826, and to Sept., 1827, when a room was built at the Institution. At first the inquiry was pursued principally as related to flint and crown glass; but in September, 1828, it was directed exclusively to the preparation and perfection of peculiar heavy and fusible glasses, from which time continued progress has been made.

In 1830 the experiments on glass-making were stopped.

In 1831 the Committee for the Improvement of Glass for Optical Purposes reported to the Royal Society Council that the telescope made with Mr. Faraday’s glass had been examined by Captain Kater and Mr. Pond. “It bears as great a power as can reasonably be expected, and is very achromatic. The Committee therefore recommend that Mr. Faraday be requested to make a perfect piece of glass of the largest size that his present apparatus will admit, and also to teach some person to manufacture the glass for general sale.”

[Sidenote: GLASS-MAKING LAID ASIDE.]

In answer to this Faraday sent the following letter to Dr. Roget, Sec. R.S.:--

[_M. Faraday to P. M. Roget._]

Royal Institution, July 4, 1831.

DEAR SIR,--I send you herewith four large and two small manuscript volumes relating to optical glass, and comprising the journal book and sub-committee book, since the period that experimental investigations commenced at the Royal Institution.

With reference to the request which the Council of the Royal Society have done me the honour of making--namely, that I should continue the investigation--I should, under circumstances of perfect freedom, assent to it at once; but obliged as I have been to devote the whole of my spare time to the experiments already described, and consequently to resign the pursuit of such philosophical inquiries as suggested themselves to my own mind, I would wish, under the present circumstances, to lay the glass aside for a while, that I may enjoy the pleasure of working out my own thoughts on other subjects.

If at a future time the investigation should be renewed, I must beg it to be clearly understood I cannot promise full success should I resume it: all that industry and my abilities can effect shall be done; but to perfect a manufacture, not being a manufacturer, is what I am not bold enough to promise.

I am, &c., M. FARADAY.

The optical glass was a failure, so far as concerned the original hope that it would lead to great improvements in telescopes. Nevertheless it furnished scientific men with a new material, the “heavy glass” consisting essentially of boro-silicate of lead, for which sundry uses in spectroscopy and other optical instruments have since been found.

In 1845 Faraday added this note:--

I consider our results as negative, except as regards any good that may have resulted from my heavy glass in the hands of Amici (who applied it to microscopes) and in my late experiments on light.

These were the famous experiments on magneto-optics and diamagnetism. Incidentally the research had led also to the permanent engagement of Sergeant Anderson as assistant to Faraday.

[Sidenote: RESEARCHES AND LECTURES.]

During these years, from 1825 to 1829, which had been thus occupied in an apparently fruitless quest, he had been far from idle. He had gone on contributing chemical papers to the _Philosophical Transactions_ and to the _Quarterly Journal_. These dealt with sulpho-naphthalic acid, with the limits of vaporisation, with caoutchouc, bisulphide of copper, the fluidity of sulphur and phosphorus, the diffusion of gases, and the relation of water to hot polished surfaces. He had also originated at the Royal Institution the Friday evening discourses (see p. 33), the first of which he held in 1826. For some years he himself delivered no inconsiderable portion of these discourses every session. In 1826 he gave six, in 1827 three, in 1828 five, in 1829 six, and these in addition to his regular afternoon courses of six or eight lectures on some connected subject. He had also, in 1826, begun the Christmas lectures adapted to a juvenile audience, and had in 1827 given a course of twelve lectures at the London Institution in Finsbury Circus. In addition to these labours he had, in 1827, brought out the first edition of his book on “Chemical Manipulation.” In 1829 he began his lectures at the Royal Military Academy at Woolwich, which continued till 1849.

The year 1830 may be regarded as the close of the first period of Faraday’s researches, during which time, though much of his labour had been of a preparatory and even desultory kind, it had been a training for the higher work to come. He had made three notable discoveries in chemistry, the new substances benzol and butylene, and the solubility of naphthalene in sulphuric acid forming the first of a new class of bodies, the sulpho-acids. He had also made an important discovery in physics, that of the electromagnetic rotations. He had already published sixty original papers, besides many notes of lesser importance, nine of these papers being memoirs in the _Philosophical Transactions_. He had already begun to receive from learned societies, academies, and universities the recognition of his scientific attainments, and he had established firmly both his own reputation as a lecturer, and the reputation of the Royal Institution, which was the scene of his lectures.