In view of the increasing difficulty of trying to cram the entire history of the Earth into the biblical mere few thousand years, some of the more religiously inclined naturalists (but not only them) opted to rely on catastrophes such as floods as agents of rapid changes. If great expanses of time were to be denied, catastrophes appeared to be the only vehicle that could significantly shape the Earth’s surface almost instantaneously. To be sure, the distribution of marine fossils provided clear evidence for the action of flooding and glaciation in the Earth’s geological past, but many of the ardent catastrophists were at least partially motivated by their unwavering loyalty to the biblical text rather than by the scientific attestation. Richard Kirwan—one of the well-known chemists of the day—articulated this position clearly. Kirwan pitted Hutton directly against Moses in describing how dismayed he was to observe “how fatal the suspicion of the high antiquity of the globe has been to the credit of Mosaic history, and consequently to religion and morality.”

The situation started to change dramatically with the publication of Charles Lyell’s three-volume Principles of Geology in the years 1830–33. Lyell, who was also Charles Darwin’s close friend, made it clear that the catastrophist doctrine was far too frail to last as a compromise between science and theology. He decided to put aside the question of the origin of the Earth and to concentrate on its evolution. Lyell argued that the forces that sculpted the Earth—volcanism, sedimentation, erosion, and similar processes—remained essentially unchanged throughout the Earth’s history, both in their strength and in their nature. This was the idea of uniformitarianism that inspired Darwin’s concept of gradualism in the evolution of species. The basic premise was simple: If there was one thing that these slow-acting geological forces needed in order to have an appreciable effect, it was time. Lots of it. Lyell’s followers have almost abandoned the notion of a definite age altogether in favor of the rather vague “inconceivably vast” time. In other words, Lyell’s Earth was one that was almost in a steady state, with snail’s-pace changes operating over a nearly infinite time. This principle starkly contrasted with the theological estimates of some six thousand years.

To a certain extent, the world view of an immeasurably extended geological age permeated Darwin’s The Origin, even though Darwin’s own attempt to estimate the age of the Weald—the eroded valley stretching across the southeastern part of England—turned out to be disastrously flawed, and he eventually retracted it. Darwin envisaged for evolution a long sequence of phases, lasting perhaps ten million years each. There was, however, one important difference between Darwin’s stance and those of the geologists. While he indeed required long periods of time for evolution to run its course, he insisted on a directional “arrow of time”; he could not be satisfied with a steady state or a cyclical progression, since the concept of evolution gave time a clear trend. But a controversy was starting to brew. It was not between Darwin and Lyell personally, nor even between geology and biology in general, but between a champion of physics on one side and some geologists and biologists on the other. Enter one of the most eminent physicists of his time: William Thomson, later known as Lord Kelvin.

In 1897 the Vanity Fair Album, a compendium of highlights from the weekly British society magazine, published a eulogy of Lord Kelvin, part of which read as follows:

His father was Professor of Mathematics at Glasgow. Himself was born in Belfast seventy-two years ago, and educated at Glasgow University and at St Peter’s, Cambridge; of which College, after making himself Second Wrangler and Smith’s Prizeman, he was made a Fellow. Unlike a Scotchman, he presently returned to Glasgow—a Professor of Natural Philosophy; and since then he has invented so much and, despite his mathematical knowledge, has done so much good, that his name—which is William Thomson—is known not only throughout the civilized world but also on every sea. For when he was a mere knight he invented Sir William Thomson’s mariner’s compass as well as a navigational sounding machine, that is, unhappily less well known. He has also done much electrical service at sea: as engineer for various Atlantic cables, as inventor of the mirror-galvanometer and siphon recorder, and much else that is not only scientific but useful. He is so good a man, indeed, that four years ago he was enobled as Baron Kelvin of Largs; yet he is still full of wisdom, for his Peerage has not spoiled him . . . He knows all there is to know about heat, all that is yet known about Magnetism, and all that he can find out about Electricity. He is a very great, honest, and humble Scientist who has written much and done more.