The Cosmologists

The first part of the readings cover the late-17th to mid-18th century “cosmologists” who presented an interesting cluster of theories that attempted to explain the natural world. You will notice the increase of incorporated geological information (fossils, strata, mountains), and the use nature and reason as sources of authority while moving away from Scripture as literal truth. This forcasts one theme of 17th-mid 18th century natural history – the relationship between history as recorded by human records and the natural world.

Harris, section 5

This section will give you an overview of the cosmologists and some notes on a variety of these “Theories of the Earth”. The major points for you to consider what features are shared by the cosmologies, and how they fall into certain general groups.

A few things to keep in mind as you read over the material. First, the cosmologists span over a century. Over that time, the knowledge base expanded – the information available to Descartes was quite different from that used by Buffon. Second, there were some benchmarks that you should keep in mind in this historical sequence: (1) Ussher’s age of the earth estimate (4004 BC) was made in 1650; (2) Steno’s Prodomus was published in 1669; and (3) the three-fold division of mountains (Primary, Secondary and Tertiary) began around 1740 and was well established within two decades (see section 6).

Questions to think about

The “outbreak” of cosmologies is at first a rather puzzling feature, and raises some broader questions.

• General issue of evidence
  • What kind of information is used as “evidence”?
  • What geological information is incorporated into the theories?
• How did the 17th century “mechanical” theories differ from the 18th century “strata-based” theories?
  • What does each group have in common?
  • What makes each group distinctive?
• Why did the cosmologies proliferate over this time interval?

18th Century Mineralogy

The gradual recognition of the organic origin of figured stones (fossils) versus the earths (minerals) led to the seperation of these two groups into organic and inorganic forms. These readings explore the development of the study of minerals, and the increase of knowledge about the earth. One theme that runs through them is the gradual shift from Aristotelian ideas to a chemical-based framework. Along with this was the increasing use of laboratory-based analyses, and field observations of strata. All of this will lead into our examination of the geognosy synthesis that builds upon this foundation (next class).

Harris, section 6

This will give you the “big picture” on 17th to 18th century developments (focusing on minerogy and chemical approaches to stones).

Laudan, chapters 2-4

Rachel Laudan’s book is an important and provocative study of the early history of geology that stresses the German/Scandinavian mineralogy tradition. She challenged traditional notions and helped revise our perspective on this important phase in the development of geological thought. You will be reading all or parts of the chapters that summarize the development of mineralogy and their integration into geognosy in general, and the ideas of Werner in particular.

Pages 20-32 (chapter 2): This section introduces the shared framework for thinking about the earth in the 17th-18th centuries.  This selection deals with the basic “classes” of minerals and how they related to the Aristotelian/Platonic/medieval ideas.  (Note the tension between composition and form, p. 27.)  Pages 30-32 lay out the basic advances through about 1700 with particular attention to the issue of mineral composition, rocks as “mixts”, and consolidation.

Pages 44-46 (chapter 2): Skipping most of the cosmologies, this short section summarizes the work of Becher – who presented a “chemical cosmology”.  (If we have mechanical cosmologies, why not a chemical one?)  Two key items to note for what follows: (1) the “earth” principle/element was subdivided (p. 45) – a significant step away from changing ratios of Aristotelian elements; and (2) he influenced Stahl who taught most of the early 18th century chemistry, and who introduced the idea of “phlogiston” (don’t worry we are not going to dive into that).

Pages 47-68 (chapter 3): This section has three main topics. First is the development of institutional support for activities that contributed to the development of mineralogy and ultimately geology (p. 47-56). Pages 56-65 is a key section that discuss advances in knowledge that contributed to the development of mineralogy in the eighteenth century. The last section (p. 66-68) returns to the “big picture” of chemical cosmologies and how the developing chemical approach was beginning to be integrated with knowledge of strata and mountain structure.

Pages 78-middle of 83: Skipping most of chapter 4 that deals with the “botanical model” (using form to classify minerals and rocks instead of chemical composition), we arrive at the discussion of the acceptance of using a chemical basis for classification and and introduction to Abraham Werner.

Arduino’s 1758 field section

Before turning to the details of geognosy, it is worth taking a quick look at one of the more detailed field sections of the mid-eighteenth century – Giovanni Arduino’s sketch of the Agno Valley. This is an outstanding example of the growing knowledge of strata as it exists in the field. The section illustrates one wall of the valley – see the geological map. I have translated the caption to the figure as presented in Ezio Vaccari’s biography of Arduino (1993): Arduino packet

Questions

• Central Europe had a very different institutional support structure than in Britian and France.
  • Why was government support available in continental Europe?
  • What was the impact of these supports?
• The concept of a few (four) mineral classes was widely adopted (Laudan, ch 2).
  • What were they?  How are they characterized?
  • How did they relate to Aristotelian/medieval ideas?
• Why was consolidation important? (Laudan ch 2 & 3; Harris notes)
  • What were the basic models for consolidation?
  • What was the relationship to lab studies of minerals?
• Laudan divides the discussion on 18th century “Advances in Mineralogy” (chapter 3) into four sections. What is the key development of each?
• The distinction of Primary, Secondary and Tertiary rocks was a fundamental step in the development of geology. Try to make a sketch of the relations between these broad units. How do these rocks differ from each other?
• On classification
  • Why was the use of a form-based classification (the botanical model) rejected in favor of a chemical classification?
  • What is the difference between a mineral classification and a system for identifying minerals?
• Consider if you were a naturalist around 1770.
  • What basic information would you have to use in making a history of the earth?
  • What connections could you make between them?
  • If you used the chemical approach, what would you tend to stress?

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