Lyell's geological interests ranged from volcanoes and geological dynamics through stratigraphy, paleontology, and glaciology to topics that would now be classified as prehistoric archaeology and paleoanthropology. He is best known, however, for his role in popularising the doctrine of uniformitarianism.
Uniformitarianism
From 1830 to 1833 his multi-volume
Principles of Geology was published. The work's subtitle was "An attempt to explain the former changes of the Earth's surface by reference to causes now in operation", and this explains Lyell's impact on science. He drew his explanations from field studies conducted directly before he went to work on the founding geology text. He was, along with the earlier John Playfair, the major advocate of James Hutton's idea of uniformitarianism, that the earth was shaped entirely by slow-moving forces still in operation today, acting over a very long period of time. This was in contrast to catastrophism, a geologic idea of abrupt changes, which had been adapted in England to support belief in Noah's flood. The two terms,
uniformitarianism and
catastrophism, were both coined by William Whewell; in 1866 R. Grove suggested the simpler term
continuity for Lyells's view, but the old terms persisted. In various revised editions (twelve in all, through 1872),
Principles of Geology was the most influential geological work in the middle of the 19th century, and did much to put geology on a modern footing. For his efforts he was knighted in 1848, then made a baronet in 1864.
Geological Surveys
Lyell noted the “economic advantages” that geological surveys could provide, citing their felicity in mineral-rich countries and provinces. Modern surveys, like the U.S. Geological Survey, map and exhibit the natural resources within the country. So, in endorsing surveys, as well as advancing the study of geology, Lyell helped to forward the business of modern extractive industries, such as the coal and oil industry.
Volcanoes and geological dynamics
Before the work of Lyell, phenomena such as earthquakes were understood by the destruction that they wrought. One of the contributions that Lyell made in
Principles was to explain the cause of earthquakes. Lyell, in contrast focused on recent earthquakes (150 yrs), evidenced by surface irregularities such as faults, fissures, stratigraphic displacements and depressions.Lyell's work on volcanoes focused largely on Vesuvius and Etna, both of which he had earlier studied. His conclusions supported gradual building of volcanoes, so-called "backed up-building", as opposed to the upheaval argument supported by other geologists.
Stratigraphy
Lyell's most important specific work was in the field of stratigraphy. From May 1828, until February 1829, he traveled with Roderick Impey Murchison (1792-1871) to the south of France (Auvergne volcanic district) and to Italy. In these areas he concluded that the recent strata (rock layers) could be categorized according to the number and proportion of marine shells encased within. Based on this he proposed dividing the Tertiary period into three parts, which he named the Pliocene, Miocene, and Eocene.
Glaciers
In
Principles of Geology (first edition, vol. 3, Ch. 2, 1833) Lyell proposed that icebergs could be the means of transport for erratics. During periods of global warming, ice breaks off the poles and floats across submerged continents, carrying debris with it, he conjectured. When the iceberg melts, it rains down sediments upon the land. Because this theory could account for the presence of diluvium, the word
drift became the preferred term for the loose, unsorted material, today called
till. Furthermore, Lyell believed that the accumulation of fine angular particles covering much of the world (today called loess) was a deposit settled from mountain flood water. Today some of Lyell's mechanisms for geologic processes have been disproven, though many have stood the test of time. His observational methods and general analytical framework remain in use today as foundational principles in geology.
Evolution
Lyell first received a copy of one of Lamarck's books from Mantell in 1827, when he was on circuit. He thanked Mantell in a letter which includes this enthusiastic passage:
- "I devoured Lamark... his theories delighted me... I am glad that he has been courageous enough and logical enough to admit that his argument, if pushed as far as it must go, if worth anything, would prove that men may have come from the Ourang-Outang. But after all, what changes species may really undergo!... That the Earth is quite as old as he supposes, has long been my creed..."
In the second volume of the first edition of
Principles Lyell explicitly rejected the
mechanism of Lamark on the transmutation of species, and was doubtful whether species were mutable. However, privately, in letters, he was more open to the possibility of evolution:
- "If I had stated... the possibility of the introduction or origination of fresh species being a natural, in contradisctinction to a miraculous process, I should have raised a host of prejudices against me, which are unfortunately opposed at every step to any philosopher who attempts to address the public on these mysterious subjects".
This letter makes it clear that his equivocation on evolution was, at least at first, a deliberate tactic. As a result of his letters and, no doubt, personal conversations, Huxley and Haeckel were convinced that, at the time he wrote
Principles, he believed new species had arisen by natural methods. Both Whewell and Sedgwick wrote worried letters to him about this.
Later, Darwin became a close personal friend, and Lyell was one of the first scientists to support
On the Origin of Species, though he did not subscribe to all its contents. Lyell was also a friend of Darwin's closest colleagues, Hooker and Huxley, but unlike them he struggled to square his religious beliefs with evolution. This inner struggle has been much commented on. He had particular difficulty in believing in natural selection as the main motive force in evolution.
Lyell and Hooker were instrumental in arranging the peaceful co-publication of the theory of natural selection by Darwin and Alfred Russel Wallace in 1858: each had arrived at the theory independently. Lyell's data on stratigraphy were important because Darwin thought that populations of an organism changed slowly, requiring "geologic time".
Although Lyell did not publicly accept evolution (descent with modification) at the time of writing the
Principles, after the Darwin-Wallace papers and the
Origin Lyell wrote in his notebook:
- May 3, 1860: "Mr. Darwin has written a work which will constitute an era in geology & natural history to show that... the descendants of common parents may become in the course of ages so unlike each other as to be entitled to rank as a distinct species, from each other or from some of their progenitors".
Lyell's acceptance of natural selection, Darwin's proposed mechanism for evolution, was equivocal, and came in the tenth edition of
Principles.
The Antiquity of Man (published in early February 1863, just before Huxley's
Man's place in nature) drew these comments from Darwin to Huxley:
- "I am fearfully disappointed at Lyell's excessive caution" and "The book is a mere 'digest' ".
Quite strong remarks: no doubt Darwin resented Lyell's repeated suggestion that he owed a lot to Lamarck, whom he (Darwin) had always specifically rejected. Darwin's daughter Henrietta (Etty) wrote to her father: "Is it fair that Lyell always calls your theory a modification of Lamarck's?"
In other respects
Antiquity was a success. It sold well, and it "shattered the tacit agreement that mankind should be the sole preserve of theologians and historians". But when Lyell wrote that it remained a profound mystery how the huge gulf between man and beast could be bridged, Darwin wrote "Oh!" in the margin of his copy.
