physical changes went on in the past at the slow rate at which they take place now; and by a simple application of the rule of three, to the sedimentary rocks, demanded as much time as the above for a small portion of the secondary period. In the Earth they discovered no trace of a beginning, no indication of an end; and some of them, leaving the solid crust of the Earth, and looking out into the Universe could see no signs of age or decay in the solar system. The biologists too were explaining the evolution of forms by unlimited amounts of time. The great Darwin spoke of the proposed limitation of geological time as one of his "sorest troubles." It was indeed inevitable that a clash should come.
Four years later, 1866, Sir William Thomson read another paper to the Edinburgh Society, "The doctrine of uniformity in geology briefly refuted." It contained only a few sentences and was a formal indictment of the fundamental doctrine of the geologists. The geologists put up Prof. Huxley to defend them; which he did in an address to the Geological Society of London in 1869. We have seen in a previous lecture how much Huxley knew of the nature of mathematics; he was scared at a few italic letters, particularly if they were small, not to mention the more formidable . He could not discuss Thomson's arguments scientifically, all he could do was to make fun of them, and encourage his colleagues in their indifference. He said, as an introduction, "I do not suppose that at the present day any geologist would be found to maintain absolute uniformitarianism, to deny that the rapidity of the rotation of the Earth may be diminishing, that the Sun may be waxing dim, or that the Earth itself may be cooling. Most of us, I suspect, are Gallios, 'who care for none of these things,' being of opinion that, true or fictitious they have made no practical difference to the Earth, during the period of which a record is preserved in stratified deposits." If researches which are the outcome of dynamical reasoning, combined with observational and experimental data, applied to determine the constancy of the length of the day, the intensity of sunshine in different
