As we have seen, Thomson had the keen, racy wit of his race. Lecturing before the members of the Birmingham and Midland Institute in 1883, he placed himself and his nationality on record in a very humorous way. His subject was "The six gateways of Knowledge." As will be remembered by the readers of The Pilgrim's Progress, old Bunyan likened the soul to a citadel on a hill having no means of communication with the outer world save by live gates, viz., the eye gate, the ear gate, the mouth gate, the nose gate and the feel gate. These are the five senses by which we obtain our knowledge of the material world which surrounds us. But Prof. Thomson took issue with Bunyan, with Reid, and the metaphysicians of all time in maintaining in this lecture that we have six gateways of knowledge instead of five, justifying the position which he took by affirming that the sense of touch is really twofold, one of heat and the other of force. It does not appear, however, that he made any marked impression on the philosophic thought of the day, for psychologists continued to write with undisturbed equanimity of the five senses and not the six.
It was on this occasion that Prof. Thomson said: "The only census of the senses, so far as I am aware, that ever before made them more than five was the Irishman's reckoning of seven senses. I presume the Irishman's seventh sense was common sense; and I believe that the possession of that virtue by my countrymen, I speak as an Irishman, I say the large possession of the seventh sense which I believe Irishmen have, will do more to alleviate the woes of Ireland than the removal of 'the melancholy ocean' which surrounds its shores."
For the successful operation of cables, telegraph lines and scientific investigations of all sorts, a system of practical electrical units, accepted by all companies and countries of the world, was soon found to be indispensable. The pioneer in the movement for establishing an international system of electrical standards was Mr. J. Latimer Clark, who, assisted by his distinguished partner, (Sir) Charles Bright, prepared a paper on "The formation of Standards of Electrical Quantity and Resistance," which was read at the Manchester meeting of the British Association in 1861. Prof. Thomson was present; and, at his instance, a committee was appointed to report on the general question of electrical units. This was the first meeting of a committee that was destined to accomplish much in the electric and electromagnetic field; it was the initial impulse of a movement that brought renown to the entire body of English electricians. Such units as the ohm, the volt and the farad met with immediate acceptance, while later on the ampere, the coulomb, the watt and the joule were introduced. Among the members of this body besides Prof. Thomson, were such able men as Clerk Maxwell, Joule, Lord Rayleigh, Sir William Siemens, Johnstone Stoney, Balfour Stewart, and Carey Foster.
The world is then indebted to the insistence and advocacy of Prof. Thomson for the general acceptance of the "C.G.S." system of measurement, which involves the centimeter (length), the gram (mass), and the second (time) as the fundamental units from which all others are derived.
Prof. Thomson has claims in the "wireless" field also; for as far back as 1855, he studied the nature of the discharge of a condenser and proved mathematically that, under certain conditions easily realized in practice, such discharges are of an oscillatory character, consisting of a forward and a backward rush of electricity between the two coatings of the condenser. As pointed out on page 92, Prof. Henry had reached the same conclusion in 1842, and Helmholtz in 1847; but Thomson's insight into the phenomenon is keen and his mathematical analysis of it very remarkable.
Just as the to-and-fro motions of the prongs of a tuning-fork give rise to sound-waves in the air, so the electric oscillation due to a condenser discharge sets up in the universal ether electric waves which flash the news of the world over continents and oceans with unthinkable velocity.
By special request, Sir William Thomson gave, in 1884, a course of lectures at the Johns Hopkins University, Baltimore, to an audience of "professional fellow-students in physical science," as he called the élite of American men of science, twenty-one in number, assembled to hear him. These accomplished physicists he also affectionately called his "twenty-one coefficients."
The subject was the wave-theory of light, and the object of the lecturer was to show how far the phenomena of light, such as its transmission, refraction and dispersion, could be explained within the limits of the elastic solid theory of the ether, which makes that hypothetical medium rigid, highly elastic and non-gravitational. From the very first lecture, Sir William assumed a cold and diffident attitude toward the rival theory of Clerk Maxwell, which makes light an electromagnetic phenomenon; and though his own presented formidable difficulties, and its rival was universally accepted, the veteran Professor assured his hearers that the elastic solid theory is the "only tenable foundation for the wave-theory of light in the present (1884) state of our knowledge."
Despite the energy which he displayed, his luminous argumentation and close logic, Kelvin made no converts among his "twenty-one coefficients"; and it soon became evident that he was championing a lost cause. Newton did the same when he held tenaciously to the corpuscular theory of light; and in doing so, let it be said, that he retarded the acceptance of the wave-theory and the advance of science by a hundred years.
A few years after the Baltimore lectures, official recognition of his distinguished services and of his eminence in science came to Sir William Thomson when, in 1892, he was raised to the peerage, with the title of Baron Kelvin of Netherhall, Kelvin being the name of a stream which passes near the buildings of the University of Glasgow and flows into the Clyde, while Netherhall is that of his country-seat at Largs, in Ayrshire, 40 miles from Glasgow.