Harris, section 14

Rudwick (1990) 

“The Principles of Geology” is Lyell’s most influential geological work. It went through many editions as he revised it to incorporate new geological information and to address his critics. It is not often read today due to its length (~1350 pages) but is very readable and available through an inexpensive University of Chicago Press reprint. Rudwick reworked one of his earlier papers to provide this introduction and summary. In reading this summary, you will miss is the amazing amount of detail and examples that Lyell incorporated into his text that illustrate the dramatic expansion of knowledge since Cuvier’s work just 15 years earlier. 

We are largely reading this to understand Lyell’s geological framework. This is usually termed “uniformitarianism” (a term given by one of his critics) but it is actually a combination of actualism (= reliance on processes now in operation), gradualism (= processes act at the same rate as observed today) and steady-state (= pattern of geological changes fluctuate around a mean) assumptions/assertions. (You will be reading more about this analysis in a week or so.) Another feature is that Lyell carefully constructed his work as a sustained argument for his view of earth history across all three volumes. His colleagues recognized his aims from the start (based on contemporary reviews and comments) but modern readers sometimes miss the importance of the last volume in focusing on the process information (volumes I and II) or just volume II (which influenced Darwin). Here are some questions to consider as you read Rudwick’s summary.

• Volume I
  • Climate model
    • How does Lyell’s model work? (I can help with this in class)
    • What was the evidence for this model in the stratigraphic record? Was the application successful? What were the limitations?
    • Why did Lyell make this model so prominent? What was he trying to achieve?
  • Physical processes
    • What is the range of processes described?
    • What kind of evidence/information did he utilize?
    • What does the arrangement of information suggest?
    • What does the reader take away in terms of
      • the potential of modern processes?
      • the argument for steady-state conditions?
• Volume II: Biological processes
  • Appearances of species was a difficulty problem at the time.
    • What is Lyell’s position on the appearances of species?
    • Why did he object to “transmutation”?
  • What did he view as the underlying causes of extinctions?
  • How did appearances and extinctions work together to present a picture of the organic world “subject to perpetual flux”?
  • What was the tempo of this flux?
  • Finally, why were molluscs preferable to terrestrial quadrupeds for reconstructing the past?
• Volume III: Earth history
  • Begins with a summary of some principles of historical geology (superposition and so forth) – you know these fairly well from your geology classes.
  • The section on Tertiary stratigraphy was his major stratigraphic contribution.
    • What was the basis for sorting out Tertiary strata?
    • How did he use his point about the significance of molluscs in Volume II?
    • How did this depend upon his ideas on the tempo of changes in the organic world?
    • Notice the arrangement of examples (really case studies) to illustrate Tertiary strata and the consistency and persistence of different environmental settings. How does this reflect his commitment to actualism, gradualism and steady-state positions?
  • Pre-Tertiary
    • Treated much more briefly.
    • How does his treatment of Secondary strata (and the contrasts with Tertiary strata) link to his climate model?
    • We will look at the competing uplift and tectonic models (Von Buch and Elie de Beaumont) in a couple of classes so don’t worry too much about them.
    • How does his interpretation of Primary strata follow Hutton’s model?

A final point on Lyell. Different commentators have argued over whether his most basic commitment was to actualism, gradualism or steady-state components. There is no easy answer to this one. I tend to look at how he arranged his argument across all three volumes (particularly Volume III) in trying to figure this out.

Lyell (1830, 1833): Introductions to Volumes I and III 

These are two short chapters that are the introductions to Volumes I and III. The first is interesting because of how it clearly illustrates the fourth scientific practice identified by Rudwick (1996) as central to the development of geology. As in Cuvier, Lyell draws analogies with the study of human history. 

The second introduction also uses many analogies but the focus has shifted to Lyell’s response to some of his critics. Notice that this a attack relies upon an appeal to actualism, but does he ever really defend his steady-state position?

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