Creationists such as Terry Mortension attempt to strengthen the illusion of a worldview difference between secular geology and flood geology as well as secular and young earth astronomy by stating many of the early uniformitarians were deistic and atheistic.
While this is true, not all early long-agers were atheists or deists;
Emmanuel Swedenborg (1688-1772) A Swedish mystic and scientist who proposed a form of the Nebular Hypothesis on the origin of the Solar System, although he also studied philosophy, physics, and mechanics; he even drew a sketch for a flying machine. Along with being a rationalist he was also a mystic and claimed to have received visions from God telling him to reform the true Christianity. Although he did hold some heterodox and other downright heretical views about the trinity (Newton did as well, not that holding heterodox views pf the trinity is a good thing of course, it is simply that even though Newton did have unorthodox views he is praised by creationists as a Christian in science), he could nonetheless be described as a Christian, and he could also be described as uniformitarian in his thinking towards natural history. He obviously had a very strong belief in the bible and that did not stop him from being a long age astronomer.
Emmanuel Kant (1724-1804) An influential German enlightenment thinker; most of his works are on philosophy although he did develop the Nebular Hypothesis which gave a naturalistic for the origin of the Solar System. Although most of his scientific work was in astronomy he did write on the history of the earth as well.
More recent scientists include who contributed to the more controversial parts of secular science include Roman Catholic Georges Lemaitre who developed the Big Bang theory, (this is interesting being that many creationists call the Big Bang an atheistic idea when in fact it sprang from the mind of a clergymen!) Jesuit scientist Pierre Teilhard de Chardin who contributed to the field of evolutionary biology (although his theology was in the stratosphere), and evolutionary biologist Theodosius Dobzhansky.
These are just two 18th century uniformitarians who were indeed Christian theists, many Christian Geologists and Astronomers who believed in an old earth came later in the 19th century when more evidence for such ideas had come. Interestingly enough creationists who were contemporaries of Darwin were often old earthers, among them being Paleontologist Sir Richard Owen and the Theologian Charles Hodge. It is simply not true that all supporters of an old earth had deistic or atheistic philosophies, There were differing views on both sides in both centuries. Belief in an old earth was not because of compromise with an anti-theistic philosophy it was simply because of the evidence for an old earth.