Here again we may quote from the Bangor address:
"Soon after I entered my present chair in the University of Glasgow in 1846 I had occasion to undertake some investigations of electrodynamic qualities of matter, to answer questions suggested by the results of mathematical theory, questions which could only be answered by direct experiment. The labour of observing proved too heavy, much of it could scarcely be carried on without two or more persons, working together. I therefore invited students to aid in the work. They willingly accepted the invitation, and lent me most cheerful and able help. Soon after, other students, hearing that their class-fellows had got experimental work to do, came to me and volunteered to assist in the investigation. I could not give them all work in the particular investigation with which I had commenced—'the electric convection of heat'—for want of means and time and possibilities of arrangement, but I did all in my power to find work for them on allied subjects (Electrodynamic Properties of Metals, Moduluses of Elasticity of Metals, Elastic Fatigue, Atmospheric Electricity, etc.). I then had an ordinary class of a hundred students, of whom some attended lectures in natural philosophy two hours a day, and had nothing more to do from morning till night. These were the balmy days of natural philosophy in the University of Glasgow—the pre-Commissional days. But the majority of the class really had very hard work, and many of them worked after class-hours for self-support. Some were engaged in teaching, some were city-missionaries, intending to go into the Established Church of Scotland or some other religious denomination of Scotland, or some of the denominations of Wales, for I always had many Welsh students. In those days, as now, in the Scottish Universities all intending theological students took a 'philosophical curriculum'—'zuerst collegium logicum,' then moral philosophy, and (generally last) natural philosophy. Three-fourths of my volunteer experimentalists used to be students who entered the theological classes immediately after the completion of the philosophical curriculum. I well remember the surprise of a great German professor when he heard of this rule and usage: 'What! do the theologians learn physics?' I said, 'Yes, they all do; and many of them have made capital experiments. I believe they do not find that their theology suffers at all from (their) having learned something of mathematics and dynamics and experimental physics before they enter upon it.'"
This statement, besides throwing an interesting light on the conditions of university work sixty years ago, gives an illustration of the wide interpretation in Scotland of the term Arts. Here it has meant, since the Chair of Natural Philosophy was founded in 1577, and held by one of the Regents of the University, Artes Liberales in the widest sense, that is, the study of Litteræ Humaniores (including mental and moral philosophy) and physical and mathematical science. These were all deemed necessary for a liberal education at that time: in the scientific age in which we live it is more imperative than ever that neither should be excluded from the Arts curriculum of our Universities. The common distinction between Arts and Science is a false one, and the product of a narrow idea which is alien to the traditions of our northern Universities.
It is to be noted, however, that the laboratory thus founded was essentially a research laboratory; it was not designed for the systematic instruction of students in methods of experimenting. Laboratories for this purpose came later, and as a natural consequence. But for the best students, ill prepared as, no doubt, some of them were for the work of research, the experience gained in such a laboratory was very valuable. They learned—and, indeed, had to learn—in an incidental manner how to determine physical constants, such as specific gravities, thermal capacities, electric resistances, and so forth. For, apart from the Relations des Expériences of Regnault, and the magnetic and electric work of Gauss and Weber, there was no systematised body of information available for the guidance of students. Good students could branch out from the main line of inquiry, so as to acquire skill in subsidiary determinations of this kind; to the more easily daunted student such difficulties proved formidable, and often absolutely deterrent.
It is not easy for a physicist of the present day to realise the state of knowledge of the time, and so he often fails to recognise the full importance of Thomson's work. The want of precise knowledge of physical constants was to a considerable extent a consequence of the want of exact definitions of quantities to be determined, and in a much greater degree of the lack of any system of units of measurement. The study of phenomena was in the main merely qualitative; where an attempt had been made to obtain quantitative determinations, the units employed were arbitrary and dependent on apparatus in the possession of the experimenter, and therefore unavailable to others. In the department of heat, as has been said, a great beginning had been made by Regnault, in whose hands the exact determination of physical constants had become a fine art.
In electricity and magnetism there were already the rudiments of quantitative measurement. But it was only long after, when the actions of magnets and of electric currents had been much further studied, that the British Association entered on its great work of setting up a system of absolute units for the measurement of such actions. Up till then the resistance, for example, of a piece of wire, to the passage of an electric current along it, was expressed by some such specification as that it was equal to the resistance of a certain piece of copper wire in the experimenter's possession. It was therefore practically impossible for experimenters elsewhere to profit by the information. And so in other cases. An example from Thomson's papers on the "Dynamical Theory of Heat" may be cited here, though it refers to a time (1851) when some progress towards obtaining a system of absolute units had been made. In § 118 (Art. XLVIII) he states that the electromotive force of a thermoelectric couple of copper and bismuth, at temperatures 0° C. and 100° C. of its functions, might be estimated from a comparison made by Pouillet of the strength of the current sent by this electromotive force through a copper wire 20 metres long and 1 millimetre in diameter, with the strength of a current decomposing water at a certain rate, were it not that the specific resistances of different specimens of copper are found to differ considerably from one another. Hence, though an estimate is made, it is stated that, without experiments on the actual wire used by Pouillet, it was impossible to arrive at an accurate result. Now if it had been in Pouillet's power to determine accurately the resistance of his circuit in absolute units, there would have been no difficulty in the matter, and his result would have been immediately available for the estimate required.
When submarine cables came to be manufactured and laid all this had to be changed. For they were expensive; an Atlantic cable, for example, cost half a million sterling. The state of the cable had to be ascertained at short intervals during manufacture; a similar watch had to be kept upon it during the process of laying, and afterwards during its life of telegraphic use. The observations made by one observer had therefore to be made available to all, so that, with other instruments and at another place, equivalent observations could be made and their results quantitatively compared with those of the former. To set up a system of measurement for such purposes as these involved much theoretical discussion and an enormous amount of experimental investigation. This was undertaken by a special committee of the Association, and a principal part in furnishing discussions of theory and in devising experimental methods was taken by Thomson. The committee's investigations took place at a date somewhat later in Thomson's career than that with which we are here dealing, and some account of them will be given in a later chapter; but much work, preparatory for and leading up to the determination of electrical standards, was done by the volunteer laboratory corps in the transformed wine-cellar of the old College.
The selection and realisation of electrical standards was a work of extraordinary importance to the world from every point of view—political, commercial, and social. It not only rendered applications of electricity possible in the arts and industries, but by relieving experimental results from the vagueness of the specifications formerly in use, made the further progress of pure electrical science a matter in which every step forward, taken by an individual worker, facilitated the advance of all. But like other toilsome services, the nature of which is not clear to the general public, it has never received proper acknowledgment from those who have profited by it. If Thomson had done nothing more than the work he did in this connection, first with his students and later with the British Association Committee, he would have deserved well of his fellow-countrymen.
When Professor Thomson was entering on the duties of his chair, and calling his students to his aid, the discoveries of Faraday on the induction of currents by the motion of magnets in the neighbourhood of closed circuits of wire, or, what comes to the same thing, the motion of such circuits in the "fields" of magnets, had not been long given to the world, and were being pondered deeply by natural philosophers. The time was ripe for a quantitative investigation of current induction, like that furnished by the genius of Ampère after the discovery by Oersted of the deflection of a magnet by an electric current. Such an investigation was immensely facilitated by Faraday's conception of lines of magnetic force, the cutting of which by the wire of the circuit gave rise to the induced current. Indeed, the mathematical ideas involved were indicated, and not obscurely, by Faraday himself. But to render the mathematical theory explicit, and to investigate and test its consequences, required the highest genius. This work was accomplished in great measure by Thomson, whose presentation of electrodynamic theory helped Maxwell to the view that light was an affair of the propagation of electric and magnetic vibrations in an insulating medium, the light-carrying ether.
Another investigation on which he had already entered in 1847 was of great importance, not only for pure science but for the development and proper economy of all industrial operations. The foundations on which a dynamical theory of heat was to be raised had been partly laid by Carnot and were being completed on the experimental side by James Prescott Joule, whom Thomson met in 1847 at the meeting of the British Association at Oxford. The meeting at Oxford in 1860 is memorable to the public at large, mainly on account of the discussion which took place on the Darwinian theory, and the famous dialectic encounter between Bishop Wilberforce and Professor Huxley; the Oxford meeting of 1894 will always be associated with the announcement of the discovery of argon by Lord Rayleigh and Sir William Ramsay: the meeting of 1847 might quite as worthily be remembered as that at which Joule laid down, with numerical exactitude, the first law of thermodynamics. Joule brought his experimental results before the Mathematical and Physical Section at that meeting; and it appears probable that they would have received scant attention had not their importance been forcibly pointed out by Thomson. Communications thereafter passed frequently between the two young physicists, and there soon began a collaboration of great value to science, and a friendship which lasted till the death of Joule in 1884. [See p. [88] below.]