As three of you immediately identified in your comments, last week’s crocodile mystery was the fastening in the center of a volvelle, holding the various layers in place and allowing them to turn:
Volvelles are paper wheels that are fastened to a leaf so that the discs spin independently. Some of the earliest volvelles were used for prognostication; Ramon Llull is credited with bringing the volvelle to the West in the late thirteenth century for use in his Ars Magna. Suzanne Karr describes the system of two discs of letters on top of a third layer as one that did not simply aid memory but produced new knowledge:
The volvelle is probably most familiar to us as a scientific instrument and, specifically, as a device used in astronomical calculations. The source of the volvelle I featured falls into that category: Martín Cortés’s Breve compendio de la sphera y de la aite de navegar, printed in Seville in 1551, was one of the foundational texts for oceanic exploration. This volvelle is intended to help the user determine the position of the sun and the moon—turn the roundels so that their indexes (one for the sun and one for the moon) point to the appropriate days and the resulting information will provide their locations.
Breve compendio features six volvelles of varying complexity (and beauty). The other five, in the order in which they appear in the book, are below:
Breve compendio, leaf 52v
You might notice that some of them look a bit odd. The third one (leaf 73r) seems to be incomplete and the index doesn’t spin, and some of them (especially the last one, leaf 113v) look as if the roundel might be a facsimile. I haven’t closely investigated them to see if that’s the case (one might seem some clues in a close examination of the paper). One of the things you might notice, too, is that the fastening is different—only the crocodile has the button fastener, while the fourth image above (leaf 83v) stands out for not being sewn in the same manner as the others.
It wouldn’t be surprising if some of those featured replacement parts. Volvelles, like any other moving part of a book, are susceptible to wear and tear; in some cases, they are removed and repurposed. The following two images show examples from 1584 and the 1596 editions of the English translation of this work, one with the volvelle and one without (click on the images to enlarge in a new window).
Personally, I find it amazing when any volvelles survive—they can be fragile and they’re designed to be spun, both conditions that make them likely to be used up. If you’d like to find out some more about volvelles, a good place to start is with their entry in Architectures of the Book; there’s also a partial bibliography of extant volvelles; you can also browse some more images of volvelles in Jim Kuhn’s media group on Luna. Finally, if you’d like to think more about how to connect volvelles with other forms of cut-ups and digital texts, Whitney Trettien’s “Computures, Cut-ups, and Combinatory Volvelles: An Archaeology of Text-Generating Mechanisms” explores the subject in an appropriately combinatory way. 3
- Suzanne Karr, “Constructions Both Sacred and Profane: Serpents, Angels, and Pointing Fingers in Renaissance Books with Moving Parts” Yale University Library Gazette 78:3/4 (April 2004), p. 103. http://www.jstor.org/stable/40859568
- For a quick introduction to Llull and his volvelles, see Brooke Palmieri’s post, “An Introduction to Paper Computing.”
- And many thanks to Whitney and to Chad Black for help in researching volvelles and in translating Cortés’s Spanish!
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As a footnote, it’s probably worth mentioning that Anthony S. Drennan has proposed a standard for the bibliographic description of volvelles and other moveable diagrams in the most recent issue of The Library:
Drennan, Anthony S. “The Bibliographical Description of Astronomical Volvelles and Other Moveable Diagrams.” The Library 13.3 (2012): 316-339.
Aaron Pratt — December 11, 2012
The most spectacular volvelles are those in Peter Apian’s Astronomicum Caesareum
Thony C — December 11, 2012
Yes, that Drennan article is an eye-opener.
For work on volvelles, see also Richard Cunningham, “Acidental Technologies,” Digital Studies / Le champ numérique: http://www.digitalstudies.org/ojs/index.php/digital_studies/article/view/192/203
Kathleen Lynch — December 12, 2012
If anyone is interested in more contemporary volvelles, there’s a great book titled Reinventing the Wheel by Jessica Helfand. Makes a lovely coffee table book, and you can learn about What Your Corn Can Do to Help Win the War (one of the more amusingly-named examples).
Michelle Sellars — December 13, 2012
Peter Apian’s Cosmographicus Liber (over 30 printed editions before 1610) provides the best introduction to the capabilities of simple astronomical volvelles. But beware, although his Astronomicum Caesareum has quite rightly been described in recent years as ‘the most beautiful scientific book ever published’, anyone trying to decipher its huge, spectacular and complex volvelle diagrams should heed King Lear when he said ‘that way madness lies’.
Tony Drennan — December 14, 2012
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