Part 11

[21] Since writing the above I have come across a letter written by Faraday in answer to one by Captain Welier as far back as 13th Sept. 1839, in which he pointed out the mal-adjustment of the dioptric apparatus at Orfordness. In July of the following year he made lengthy suggestions to the Trinity House, in which he proposed using a flat white circle or square, half an inch across, on a piece of black paper or card, as a "focal object." This was to be looked at from outside, in order to test the regularity of the glass apparatus. He also suggested observations on the divergence by looking at this white circle at a distance of twenty feet at most. Another plan he proposed was that of lighting the lamp and putting up a white screen outside. These methods of examining he carried out very shortly afterwards at Blackwall, on French and English refractors, but it seems never to have occurred to him to place his eye in the focus, or in any other manner to observe the course of the rays from inside the apparatus.

[22] Dr. Scoffern, _Belgravia_, October 1867.

[23] Mr. Barrett, _Nature_, Sept. 19, 1872.

[24] A good instance of his caution in drawing conclusions is contained in one of his letters to me:--

"ROYAL INSTITUTION OF GREAT BRITAIN,

"_2 July, 1859_.

"MY DEAR GLADSTONE,

"Although I have frequently observed lights from the sea, the only thing I have learnt in relation to their _relative brilliancy_ is that the average of a very great number of observations would be required for the attainment of a moderate approximation to truth. One has to be some miles off at sea, or else the observation is not made in the chief ray, and then one does not know the state of the atmosphere about a given lighthouse. Strong lights like that of Cape Grisnez have been invisible when they should have been strong; feeble lights by comparison have risen up in force when one might have expected them to be relatively weak; and after inquiry has not shown a state of the air at the lighthouse explaining such differences. It is probable that the cause of difference often exists at sea.

"Besides these difficulties there is that other great one of not seeing the two lights to be compared in the field of view at the same time and same distance. If the eye has to turn 90° from one to the other, I have no confidence in the comparison; and if both be in the field of sight at once, still unexpected and unexplained causes of difference occur. The two lights at the South Foreland are beautifully situated for comparison, and yet sometimes the upper did not equal the lower when it ought to have surpassed it. This I referred at the time to an upper stratum of haze; but on shore they knew nothing of the kind, nor had any such or other reason to expect particular effects.

"Ever truly yours,

"M. FARADAY."

As an instance of his unwillingness to commit himself to an opinion unless he was sure about it, may be cited a letter he wrote to Sir G. B. Airy, the Astronomer Royal, who asked for his advice in regard to the material of which the national standard of length should be made:--"I do not see any reason why a pure metal should be particularly free from internal change of its particles, and on the whole should rather incline to the hard alloy than to soft copper, and yet I hardly know why. I suppose the labour would be too great to lay down the standard on different metals and substances; and yet the comparison of them might be very important hereafter, for twenty years seem to _do_ or _tell_ a great deal in relation to standard measures." Bronze was finally chosen.

SECTION V.

THE VALUE OF HIS DISCOVERIES.

Science is pursued by different men from different motives.

"To some she is the goddess great; To some the milch-cow of the field; Their business is to calculate The butter she will yield."

Now, Faraday had been warned by Davy before he entered his service that Science was a mistress who paid badly; and in 1833 we have seen him deliberately make his calculation, give up the butter, and worship the goddess.

For the same reason also he declined most of the positions of honour which he was invited to fill, believing that they would encroach too much on his time, though he willingly accepted the honorary degrees and scientific distinctions that were showered upon him.[25]

And among those who follow Science lovingly, there are two very distinct bands: there are the philosophers, the discoverers, men who persistently ask questions of Nature; and there are the practical men, who apply her answers to the various purposes of human life. Many noble names are inscribed in either bead-roll, but few are able to take rank in both services: indeed, the question of practical utility would terribly cramp the investigator, while the enjoyment of patient research in unexplored regions of knowledge is usually too ethereal for those who seek their pleasures in useful inventions. The mental configuration is different in the two cases; each may claim and receive his due award of honour.

Faraday was pre-eminently a discoverer; he liked the name of "philosopher." His favourite paths of study seem to wander far enough from the common abodes of human thought or the requirements of ordinary life. He became familiar, as no other man ever was, with the varied forces of magnetism and electricity, heat and light, gravitation and galvanism, chemical affinity and mechanical motion; but he did not seek to "harness the lightnings," or to chain those giants and to make them grind like Samson in the prison-house. His way of treating them reminds us rather of the old fable of Proteus, who would transform himself into a whirlwind or a dragon, a flame of fire or a rushing stream, in order to elude his pursuer; but if the wary inquirer could catch him asleep in his cave, he might be constrained to utter all his secret knowledge: for the favourite thought of Faraday seems to have been that these various forces were the changing forms of a Proteus, and his great desire seems to have been to learn the secret of their origin and their transformations. Thus he loved to break down the walls of separation between different classes of phenomena, and his eye doubtless sparkled with delight when he saw what had always been looked upon as permanent gases liquefy like common vapours under the constraint of pressure and cold--when the wires that coiled round his magnets gave signs of an electric wave, or coruscated with sparks--when the electricities derived from the friction machine and from the voltaic pile yielded him the same series of phenomena--when he recognized the cumulative proof that the quantity of electricity in a galvanic battery is exactly proportional to the chemical action--when his electro-static theory seemed to break down the barrier between the conductors and insulators, and many other barriers beside--when he sent a ray of polarized light through a piece of heavy glass between the poles of an electro-magnet, and on making contact saw that the plane of polarization was rotated, or, as he said, the light was magnetized--and when he watched pieces of bismuth, or crystals of Iceland spar, or bubbles of oxygen, ranging themselves in a definite position in the magnetic field.

"I delight in hearing of exact numbers, and the determinations of the equivalents of force when different forms of force are compared one with another," he wrote to Joule in 1845; and no wonder, for these quantitative comparisons have proved many of his speculations to be true, and have made them the creed of the scientific world. When he began to investigate the different sciences, they might be compared to so many different countries with impassable frontiers, different languages and laws, and various weights and measures; but when he ceased they resembled rather a brotherhood of states, linked together by a community of interests and of speech, and a federal code; and in bringing about this unification no one had so great a share as himself.

He loved to speculate, too, on Matter and Force, on the nature of atoms and of imponderable agents. "It is these things," says the great German physicist Professor Helmholz, "that Faraday, in his mature works, ever seeks to purify more and more from everything that is theoretical, and is not the direct and simple expression of the fact. For instance, he contended against the action of forces at a distance, and the adoption of two electrical and two magnetic fluids, as well as all hypotheses contrary to the law of the conservation of force, which he early foresaw, though he misunderstood it in its scientific expression. And it is just in this direction that he exercised the most unmistakeable influence first of all on the English physicists."[26]

While, however, Faraday was pre-eminently an experimental philosopher, he was far from being indifferent to the useful applications of science. His own connection with the practical side of the question was threefold: he undertook some laborious investigations of this nature himself; he was frequently called upon, especially by the Trinity House, to give his opinions on the inventions of others; and he was fond of bringing useful inventions before the members of the Royal Institution in his Friday evening discourses. The first of these, on February 3, 1826, was on India-rubber, and was illustrated by an abundance of specimens both in the raw and manufactured states. He traced the history of the substance, from the crude uncoagulated sap to the sheet rubber and waterproof fabrics which Mr. Hancock and Mr. Macintosh had recently succeeded in preparing. In this way also he continued to throw the magic of his genius around Morden's machinery for manufacturing Bramah's locks, Ericsson's caloric engine, Brunel's block machinery at Portsmouth, Petitjean's process for silvering mirrors, the prevention of dry-rot in timber, De la Rue's envelope machinery, artificial rubies, Bonelli's electric silk loom, Barry's mode of ventilating the House of Lords, and many kindred subjects.

It may not be amiss to describe the last of his Friday evenings, in which he brought before the public Mr. C. W. Siemens' Regenerative Gas Furnace. The following letter to the inventor will tell the first steps:--

"ROYAL INSTITUTION, _March 22, 1862_.

"MY DEAR SIR,

"I have just returned from Birmingham--and there saw at Chance's works the application of your furnaces to glass-making. I was very much struck with the whole matter.

"As our managers want me to end the F. evenings here after Easter, I have looked about for a thought, for I have none in myself. I think I should like to speak of the effects I saw at Chance's, if you do not object. If you assent, can you help me with any drawings or models, or illustrations either in the way of thoughts or experiments? Do not say much about it out of doors as yet, for my mind is not settled in what way (if you assent) I shall present the subject.

"Ever truly yours,

"M. FARADAY.

"C. W. SIEMENS, ESQ."

Of course the permission was gladly given, and Mr. Siemens met him at Birmingham, and for two days conducted him about works for flint and crown glass, or for enamel, as well as about ironworks, in which his principle was adopted, wondering at the Professor's simplicity of character as well as at his ready power of grasping the whole idea. Then came the Friday evening, 20th June, 1862, in which he explained the great saving of heat effected, and pictured the world of flame into which he had gazed in some of those furnaces. But his powers of lecturing were enfeebled, and during the course of the hour he burnt his notes by accident, and at the conclusion he very pathetically bade his audience farewell, telling them that he felt he had been before them too long, and that the experience of that evening showed he was now useless as their public servant, but he would still endeavour to do what he could privately for the Institution. The usual abstract of the lecture appeared, but not from his unaided pen.

Inventors, and promoters of useful inventions, frequently benefited by the advice of Faraday, or by his generous help. A remarkable instance of this was told me by Cyrus Field. Near the commencement of his great enterprise, when he wished to unite the old and the new worlds by the telegraphic cable, he sought the advice of the great electrician, and Faraday told him that he doubted the possibility of getting a message across the Atlantic. Mr. Field saw that this fatal objection must be settled at once, and begged Faraday to make the necessary experiments, offering to pay him properly for his services. The philosopher, however, declined all remuneration, but worked away at the question, and presently reported to Mr. Field:--"It can be done, but you will not get an instantaneous message." "How long will it take?" was the next inquiry. "Oh, perhaps a second." "Well, that's quick enough for me," was the conclusion of the American; and the enterprise was proceeded with.

As to the electric telegraph itself, Faraday does not appear among those who claim its parentage, but he was constantly associated with those who do; his criticisms led Ritchie to develop more fully his early conception, and he was constantly engaged with batteries and wires and magnets, while the telegraph was being perfected by others, and especially by his friend Wheatstone, whose name will always be associated with what is perhaps the most wonderful invention of modern times.

As to Faraday's own work in applied science, his attempts to improve the manufacture of steel, and afterwards of glass for optical purposes, were among the least satisfactory of his researches. He was more successful in the matter of ventilation of lamp-burners. The windows of lighthouses were frequently found streaming with water that arose from the combustion of the oil, and in winter this was often converted into thick ice. He devised a plan by which this water was effectually carried away, and the room was also made more healthy for the keepers. At the Athenæum Club serious complaints were made that the brilliantly lighted drawing-room became excessively hot, and that headaches were very common, while the bindings of the books were greatly injured by the sulphuric acid that arose from the burnt coal-gas. Faraday cured this by an arrangement of glass cylinders over the ordinary lamp chimneys, and descending tubes which carried off the whole products of combustion without their ever mixing with the air of the room. This principle could of course be applied to brackets or chandeliers elsewhere, but the Professor made over any pecuniary benefit that might accrue from it to his brother, who was a lamp manufacturer, and had aided him in the invention.

The achievements of Faraday are certainly not to be tested by a money standard, nor by their immediate adaptation to the necessities or conveniences of life. "Practical men" might be disposed to think slightly of the grand discoveries of the philosopher. Their ideas of "utility" will probably be different. One man may take his wheat corn and convert it into loaves of bread, while his neighbour appears to lose his labour by throwing the precious grain into the earth: but which is after all most productive? The loaves will at once feed the hungry, but the sower's toil will be crowned in process of time by waving harvests.

Yet some of Faraday's most recondite inquiries did bear practical fruit even during his own lifetime. In proof of this I will take one of his chemical and two of his electrical discoveries.

Long ago there was a Portable Gas Company, which made oil-gas and condensed it into a liquid. This liquid Faraday examined in 1824, and he found the most important constituent of it to be a light volatile oil, which he called bicarburet of hydrogen. The gas company, I presume, came to an end; but what of the volatile liquid? Obtained from coal-tar, and renamed Benzine or Benzol, it is now prepared on a large scale, and used as a solvent in some of our industrial arts. But other chemists have worked upon it, and torturing it with nitric acid, they have produced nitrobenzol--a gift to the confectioner and the perfumer. And by attacking this with reducing agents there was called into existence the wondrous base aniline,--wondrous indeed when we consider the transformations it underwent in the hands of Hofmann, and the light it was made to throw on the internal structure of organic compounds. Faraday used sometimes to pay a visit to the Royal College of Chemistry, and revel in watching these marvellous reactions. But aniline was of use to others besides the theoretical chemist. Tortured by fresh appliances, this base gave highly-coloured bodies which it was found possible to fix on cotton as well as woollen and silken fabrics, and thence sprang up a large and novel branch of industry, while our eyes were delighted with the rich hues of mauve and magenta, the Bleu de Paris, and various other "aniline dyes."

Everyone who is at all acquainted with the habits of electricity knows that the most impassable of obstacles is the air, while iron bolts and bars only help it in its flight: yet, if an electrified body be brought near another body, with this invisible barrier between them, the electrical state of the second body is disturbed. Faraday thought much over this question of "induction," as it is called, and found himself greatly puzzled to comprehend how a body should act where it is not. At length he satisfied himself by experiment that the interposed obstacle is itself affected by the electricity, and acquires an electro-polar state by which it modifies electric action in its neighbourhood. The amount varies with the nature of the substance, and Faraday estimated it for such dielectrics as sulphur, shellac, or spermaceti, compared with air. He termed this new property of matter "specific inductive capacity," and figured in his own mind the play of the molecules as they propagated and for a while retained the force. Now, these very recondite observations were opposed to the philosophy of the day, and they were not received by some of the leading electricians, especially of the Continent, while those who first tried to extend his experiments blundered over the matter. However, the present Professor Sir William Thomson, then a student at Cambridge, showed that while Faraday's views were rigorously deducible from Coulomb's theory, this discovery was a great advance in the philosophy of the subject. When submarine telegraph wires had to be manufactured, Thomson took "specific inductive capacity" into account in determining the dimensions of the cable: for we have there all the necessary conditions--the copper wire is charged with electricity, the covering of gutta-percha is a "dielectric," and the water outside is ready to have an opposite electric condition induced in it. The result is that, as Faraday himself predicted, the message is somewhat retarded; and of course it becomes a thing of importance so to arrange matters that this retardation may be as small as possible, and the signals may follow one another speedily. Now this must depend not only on the thickness of the covering, but also on the nature of the substance employed, and it was likely enough that gutta-percha was not the best possible substance. In fact, when Professor Fleeming Jenkin came to try the inductive capacity of gutta-percha by means of the Red Sea cable, he found it to be almost double that of shellac, which was the highest that Faraday had determined, and attempts have been made since to obtain some substance which should have less of this objectionable quality and be as well adapted otherwise for coating a wire. There is Hooper's material, the great merit of which is its low specific inductive capacity, so that it permits of the sending of four signals while gutta-percha will only allow three to pass along; and Mr. Willoughby Smith has made an improved kind of gutta-percha with reduced capacity. Of course no opinion is expressed here on the value of these inventions, as many other circumstances must be taken into account, such as their durability and their power of insulation,--that is, preventing the leakage of the galvanic charge; but at least they show that one of the most abstruse discoveries of Faraday has penetrated already into our patent offices and manufactories. Two students in the Physical Laboratory at Glasgow have lately determined with great care the inductive capacity of paraffin, and there can be little doubt that the speculations of the philosopher as to the condition of a dielectric will result in rendering it still more easy than at present to send words of information or of friendly greeting to our cousins across the Atlantic or the Indian Ocean.

The history of the magneto-electric light affords another remarkable instance of the way in which one of Faraday's most recondite discoveries bore fruit in his own lifetime; and it is the more interesting as it fell to his own lot to assist in bringing the fruit to maturity.

"BRIGHTON, _November 29, 1831_.

"DEAR PHILLIPS,

"For once in my life I am able to sit down and write to you without feeling that my time is so little that my letter must of necessity be a short one; and accordingly I have taken an extra large sheet of paper, intending to fill it with news.

"But how are you getting on? Are you comfortable? And how does Mrs. Phillips do; and the girls? Bad correspondent as I am, I think you owe me a letter; and as in the course of half an hour you will be doubly in my debt, pray write us, and let us know all about you. Mrs. Faraday wishes me not to forget to put her kind remembrances to you and Mrs. Phillips in my letter....

"We are here to refresh. I have been working and writing a paper that always knocks me up in health; but now I feel well again, and able to pursue my subject; and now I will tell you what it is about. The title will be, I think, 'Experimental Researches in Electricity:'--I. On the Induction of Electric Currents; II. On the Evolution of Electricity from Magnetism; III. On a new Electrical Condition of Matter; IV. On Arago's Magnetic Phenomena. There is a bill of fare for you; and, what is more, I hope it will not disappoint you. Now, the pith of all this I must give you very briefly; the demonstrations you shall have in the paper when printed...."

So wrote Faraday to his intimate friend Richard Phillips, on November 29th, 1831, and the letter goes on to describe the great harvest of results which he had gathered since the 29th of August, when he first obtained evidence of an electric current from a magnet. A few days afterwards he was at work again on these curious relations of magnetism and electricity in his laboratory, and at the Round Pond in Kensington Gardens, and with Father Thames at Waterloo Bridge. On the 8th of February he entered in his note-book: "This evening, at Woolwich, experimented with magnet, and for the first time got the magnetic spark myself. Connected ends of a helix into two general ends, and then crossed the wires in such a way that a blow at _a b_ would open them a little. Then bringing _a b_ against the poles of a magnet, the ends were disjoined, and bright sparks resulted."

Next day he repeated this experiment at home with Mr. Daniell's magnet, and then invited some of his best friends to come and see the tiny speck of light.[27]

But what was the use of this little spark between the shaken wires? "What is the use of an infant?" asked Franklin once, when some such question was proposed to him. Faraday said that the experimentalist's answer was, "Endeavour to make it useful." But he passed to other researches in the same field.