In 1869, Huxley delivered an address to the Geological Society, in which he postulated the existence of 'three more or less contradictory systems of geological thought,' under the names of 'Catastrophism,' 'Uniformitarianism' and 'Evolution.' In this essay, distinguished by all his wonderful lucidity and forceful logic, Huxley sought to establish the position that evolution is a doctrine, distinct from and _in advance of_ that of uniformitarianism, and that Hutton and Playfair--'and to a less extent Lyell'--had acted unwisely in deprecating the extension of Geology into enquiries concerning 'the beginning of things[15].' But there is no doubt that Huxley at a later period was led to qualify, and indeed to largely modify, the views maintained in that address. In a footnote to an essay written in April 1887, he asserts 'What I mean by "evolutionism" is consistent and thoroughgoing uniformitarianism'; and in the same year he wrote in his _Reception of the Origin of Species_[16]: 'Consistent uniformitarianism postulates evolution, as much in the organic as in the inorganic world[17].' It is not difficult to trace the causes of this change in the attitude of mind with which Huxley regarded the doctrine of 'uniformitarianism.' He assures us 'I owe more than I can tell to the careful study of the _Principles of Geology_[18],' and again 'Lyell was for others as for me the chief agent in smoothing the road for Darwin[19].' From the perusal of the letters of Lyell, published in 1881, Huxley learned that the author of the _Principles of Geology_ had, at a very early date, been convinced that evolution was true of the organic as well as of the inorganic world--though he had been unable to accept Lamarckism, or any other hypothesis on the subject that had, up to that time, been suggested. There can be little doubt, however, that a chief influence in bringing about the change in Huxley's views was his intercourse with Darwin--who was, from first to last, an uncompromising 'uniformitarian.' We are fully justified, then, in regarding the teaching of Hutton and Lyell (to which Whewell gave the name of 'uniformitarianism') as being identical with evolution. The cockpit in which the great battle between catastrophism and evolution was fought out, as we shall see in the sequel, was the Geological Society of London, where doughty champions of each of the rival doctrines met in frequent combat and long maintained the struggle for supremacy.