Although some young earthers (notably George McCready Price) have slandered William Smith as making up an old earth and inventing evidence in favor of it, the reality is that Smith’s combination of being self-taught outside the academic mainstream of geology and his single-minded focus on recognizing layers rather than wondering how they formed meant that he was actually a young-earther while doing much of his work. Eventually a couple of pastors who were friends of his explained how the evidence pointed to an old earth. William Townsend, one of those two pastors, first published a significant chunk of Smith’s data on the pattern of fossils marking different layers in his book The Character of Moses Established for Veracity as an Historian, Recording Events From the Creating to the Deluge (2 vols., 1813-1815). If you can’t figure out from the title of that book that Smith was not challenging prevailing theological views on the age of the earth, you can make a lot of money writing purported history books like The Map that Changed the World or Common-Sense Geology - Simon Winchester’s claims about the history are not remarkably more reliable than Price’s, just changing who is supposedly a hero or villain.
Lyell did not propose an old earth; the fact that geology points to an old earth was established by the mid-1770’s, over two decades before Lyell was born, and suspected over a century before his birth. Lyell’s theology was not particularly sound; like most young-earth and ID claims, his approach was deistic, claiming that God is not involved in things that happen according to scientific laws.
Steno published on common-sense observations about geological layers in the 1660’s; similar ideas were floating around elsewhere at that time (e.g., Hooke) or even earlier (da Vinci wrote such thoughts in his coded notebooks and no one else read them for a few centuries). As people began to look at geological layers, they noticed a few things:
There are a lot of layers.
The same layer can be recognized widely across Europe (and eventually elsewhere).
Many geologic layers look a lot like the layers that we see forming today as sand and mud slowly piles up here and there.
(Unlike one of Galileo’s key arguments for heliocentrism, Steno’s models were correct. They also were generally accepted, even though, like Galileo, Steno was challenging some Aristotelian assumptions, which Voltaire nearly a century later was reluctant to give up.)
The huge number of layers, many of which looked to require a long time to form and none of which seemed to have any definite trace of humans, led to increasing recognition that geology pointed to a very long pre-human history, which the Bible had apparently skipped over as being theologically irrelevant. Even Ussher had allotted some time for the chaos before the seven days, and his efforts (like those of many others) to incorporate all available historical data led directly into the incorporation of geological data into our understanding of the age of the earth. Old earth views were generally accepted as no theological problem. Michael Tuomey, in his 1848 Geology of South Carolina, has a short section discussing how well geology supports the Bible. In particular, geology points back to a beginning, against the indefinite cycles of much deistic speculation. Tuomey also describes young-earth objections to geology as a thing of the past. The first book to publish a series of pictures illustrating earth history through geologic time has a final picture of the beginning of modern time in the Garden of Eden. Atheistic and young-earth claims about old-earth being an attack on religious beliefs are untrue.