ABSTRACT

Stewart in his lectures paid special attention to the principle of the Conservation of Energy, and gave a course of lectures entirely on this subject, and naturally I puzzled my head a great deal about it, especially about the transformation of one kind of energy into another - kinetic energy into potential energy, for example. 1 found the idea of kinetic energy being transformed into something of quite a different nature very perplexing, and it seemed to me simpler to suppose that all energy was of the same kind, and that the 'transformation' of energy could be more correctly described as the transference of kinetic energy from one home to another, the effects it produced depending on the nature of its home. This had been recognised in the case of the transformation of the kinetic energy of a moving body striking against a target into heat, the energy of the heated body being the kinetic energy of its molecules, and it seemed to me that the same thing might apply to other kinds of energy. One day I plucked up courage to bring this view before Stewart. I should not have been surprised if he had regarded me as a heretic of the worst kind, and upbraided me for having profited so little from his teaching. He was, however, quite sympathetic. He did not profess to agree with it,

J.J. Thomson, around 1880

but thought it was not altogether irrational, and that it might be worth my while to develop it. [I]

Now, four or five years later, and armed with the methods of analytical dynamics, Thomson investigated the transformation of energy using a modified kagrangian formulated only four years previously by Routh in his Adams Prize Essay of 1877. The essential idea of the thesis was that all types of energy were manifestations of the kinetic energy of invisible systems.