Faraday's Diary
THE experimental researches of Faraday have exerted a profound influence Or( the development of the physical and chemical sciences. Their progress was recorded day by day in a diary which was begun in 1828, just a century ago, and was 'continued until • age and failing health brought the experimental work to a close in 1862. Faraday describes his work' in careful detail, recording all the circumstances of each experiment, lest some might be omitted 'which subsequent considera- tion would show to be essential. ` It is not surprising, therefore, that the diary runs to about a million words.
From time to time Faraday published accounts' of his work and of the conclusions he based' upon it. The diary itself has never- been -pUblislied and- remains the Royal Institution; a treasured --possession which is consulted only under special- conditions.
A cursory glance shows that he made many more observations than were required to establish his published propositions : and it is certain that there must be many observations of which the meaning was not dear to him at that time. They may now be illuminating and suggestive. No one has examined the diary thoroughly. But its greatest interest does not lie in the possibility that new deductions may be made from it, in the way that further finds of precious metal are obtained by working over the tailings of an old mine. Fascinating and fruitful as the search must be there are even greater inducements to the study of the book.
Faraday's work has been the origin of some of the most remarkable developments in thought and under- standing that the world has ever known. In his diary we read of the steps which day by day he made- towards his conclusions ; his failures and his successes are all recorded with equal care. We see the gradual dawning of great generalizations, sometimes the sudden .and triumphant leap to a conclusion of the first importance. We find passages containing the very beginnings of ideas which are now guiding principles of science and industry. And, again, we read admissions of failure, and of the need to begin again. All the workings of his mind are written down for us to follow. To the student of science the fascination is extraordinary. And he is far from being the only one to whom the account must appeal, for the matters dealt with are of general interest, and the language is remarkably free from technical terms, or at any rate from such terms unexplained. The most complicated mathematical statement is that of. the Rule of Three ! Moreover, Faraday enjoyed his work so thoroughly ; quaint little expressions of pleasure and more rarely of disappointment are scattered here and there through the story. He goes about his research in a workmanlike fashion, not rushing it, but trying to think out carefully what he is going to do. And every now and then he stops to reflect. He seems to be talking to his diary : probably he found he could most satisfac- torily clear his mind by setting his thoughts down in black and white.
One or two brief extracts will give some idea -of what the diary is like. In order to understand their allusions let us recall his main purpose ; for there certainly is one and it runs through all his work. He carried out many subsidiary researches, but his chief endeavour was to link together the various manifestations of Nature's forces, magnetism, electricity, light, gravity, chemical action, cohesion.
Thus, on August 29th, 1831, he found the famous link between electricity and magnetism on which our modern electrical industries depend. He seems to have plunged into the subject suddenly. During the summer he had been investigating with great perseverance the pretty and in their way important " crispations," or stationary waves, that are formed on the surfaces of liquid. pools lying on vibrating surfaces. The import of these experiments is but trifling compared to that of the work that immediately followed. It is startling to turn the page and realize the difference in the significance of the statements,- though the writing and the mode of telling run on connectedly, as if Faraday drew no distinction, as we should now do, between the two sets of experiments. So, on August 29th, -" when- all was ready, the moment the battery was communicated with both ends of wire at A side, the helix strongly attracted the needle after a few vibrations, it came to a state of rest in its original and natural position, and then- on breaking the battery connexion the needle was -as strongly repelled, and, -after few oscillations came to rest in the same place as before. Hence effect indirect, but transient, but its recurrence on breaking the connexion shows an equilibrium somewhere that must be capable of being rendered more distinct."
The phrases cannot be easily understood without the context which is too long to quote, but they amount to this, that while a magnet is being brought near to a coil of wire, there is a tendency for a current to run in that wire, and while the magnet is being taken away there is a tendency to cause a current in a direction opposite to the first. This is the fundamental principle of the dynamo. Moreover, the words " show an equili- brium somewhere," seem to be the first glimmer of the idea, afterwards of the greatest fruitfulness, that the seat of these actions is not in the wires but in the space about them : as it became usual to say, it was in the ether. From time to time, as we go on turning over the pages of the diary, we find this idea growing clearer and stronger. Years afterwards, when Faraday was suddenly called on to give one of the Friday Evening Discourses, because the courage of the appointed lecturer had deserted him, he poured out the thoughts on this subject which had been gathering in his mind. They came to Clark Maxwell, who developed from them the electromagnetic theory of light and those famous mathe- matical laws by which the relations between magnetism and electricity are governed.
He had many disappointments in his wide search. One of these is recorded in October, 1845. A month previously he had made another of his great discoveries ; he had found as he said, " the first true relation between magnetism and light." The theoretical importance is very high. He found that a magnet was capable of rotating the plane of polarization of light. Truly, an extraordinary and out of the way place in which to find the relation that he looked for. He was delighted with his achievement. " I have at last succeeded in illumina- ting a magnetic curve or line of force and in magnetising a ray of light." On October 11 " came forth a new and striking result." Certain optical effects appeared in a new piece of apparatus which he had made for the further study of his magnetism-light connexion. He spent two days in eager examination and writes on October 12th, " Singular and beautiful Phenomena there—No guessing what they will extend or lead to—An open door." Next day he finds his new discovery has nothing to do with Magnetism or electricity, but is merely a consequence of the casual heating of his apparatus. " Worked again on these phenomena and after much experiment and consideration made out the cause of the second effect, that of the diffuse phosphorescent light, and so though I have lost an imagined discovery have removed a stumbling- block." - The -researches on the - connexion between chemical action and electricity. were the basis of the subject of electrolysis, of such huge importance both to pure science and to -industry. - The diary contains the full story of the long series of experiments which led finally to the discovery that in- the electrolytic cell the electricity is, so to speak; done up into parcels of definite and constant size. Here-arises the conception of the atom of electricity. And as to the general relation' between the two " forces of Nature " he -writes, on February 12th, 1834, " Hence chemical action- merely electrical - action, and Electric action merely chemical." On May 18th, 1834, he .writes, " With reference to Mag(netic) -attraction can a magnet take- iron or nickel out of a very fluid amalgam." The magnetic separator is now well known to the metallurgist. " Gravity is still far weaker, .• Must consider the relation of these -three forces Chem. attraction- Cohesion and Gravity." His attempts to connect gravity with other " forces " were quite unsuccessful, though conducted with as much energy and care as any of the more successful researches. For a long time he worked at the shot tower on the south bank of the Thames, looking for possible differences in the electrical state of a body when raised or lowered through the height of the tower. He also raised and lowered a wire helix from the ceiling to the floor of the Royal Institution theatre, looking for a possible development of a current of electricity in a galvanometer connected with the helix. For some days the experiment seemed to be successful, but he found at last that the effect was false : it was due to the magnetic action of the earth upon the connecting wires as they moved. Yet at the end of his experimental researches he restates the conviction that there must be a relation between gravity and " the other forms of natural power," though, as he says on April 16th, 1860, " it might, indeed, have been anticipated from the very views I entertain, that we could hardly hope to lay hold by experiment of such an amount of gravitating force as would yield appreciable evidence of electric or heat force :—but if we were to stop the first institution of experiment in any new direction for such a reason, what progress or more, what discovery, could we hope to make by its means in any of the, as yet, undiscovered paths of science."
The connexion between gravitation and light is indeed difficult to make plain. It is to be found in the bending of a ray of light in a gravitational field, as Einstein predicted and the astronomers have verified.
Faraday's last entry is dated March 12th, 1862, and describes an attempt to find some action between a mag- net and the light emitted from a neighbouring flame. In this also he failed. Its existence was afterwards proved by the Dutch physicist Zeeman, who used apparatus of greater power and delicacy than Faraday could command.
The diary is far more than a mere record of work done. It is a most human story of the reasonings and researches of one of the greatest of experimental philosophers written by the man himself as he would have written to a
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