blog-post blog-post

Uncommon Sense

By Tamara Plakins Thornton · June 03, 2020

Global Knowledge, Eighteenth-Century Style

WMQ 8 min read

In this post, WMQ author Tamara Plakins Thornton recounts how she came to understand eighteenth-century globes and how that changed the way she needed them illustrated for her article in the April 2020 issue. 

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by Tamara Plakins Thornton

Late in the copy-editing process, one of the WMQ staff posted a query to my essay, “Mathematical Geography, the ‘Use of the Globes,’ and Race Theory in Early America.” “We will need to choose a portion of this title to use as the right running head for your article,” it read. “I am tentatively suggesting ‘Race Theory in Early America,’ but please let us know if you’d like to use something else.” I did want something else. “Race theory” addressed the “so what” question, but “the use of the globes” represented the article’s particular contribution to that scholarly conversation. It just had to make it in.

That little phrase presented me with a big problem though.  My readers would assume they knew what early globes looked like and were used for, but they would be wrong. I knew this because I had made the same mistakes. In conducting research for my last book project, I had run across the phrase “geography and the use of the globes” dozens of times in advertisements for mathematical and vocational instruction, but I had skipped right over it. Why, after all, should it have given me any pause? Unlike the “gauging” and “dialing” I had often seen in those same advertisements, I did not need to find out what the “use of the globes” might be. Clearly it referred to the same skill I had been taught in grade school, finding geographical locations on a spherical map of the world.

But when I finally followed that phrase into the sources, from globe-makers’ trade cards to globe-users’ manuals, I saw how wrong I had been. Globes, I quickly learned, came in pairs, celestial and terrestrial. By manipulating these orbs and their functional “appurtenances,” users found the answers to such space-time problems as: “The latitude being given, to tell the rising and setting of the sun, and the length of the day and night, at any time of the year.” This was the skill termed the use of the globes. What is more, to make the solutions come out right from the perspective of a terrestrial viewer, globes were not designed to be faithful representations of physical reality, as modern ones are. The terrestrial globe was not tilted on the Earth’s axis, for example, and it was meant to be spun east to west, that is, counter-factually.

After establishing what globes used to be, pedagogical tools in the now archaic discipline of “mathematical geography,” my article argues that in the early republic, “global” knowledge provided the intellectual scaffolding for a newly influential, credible, and authoritative explanation of skin color. But before I could get to any of that, I first had to introduce my readers to these unfamiliar globes and their long-vanished uses.

One way was to walk them through one of these globes’ problems. You can only teach what you know, and it’s harder than you might think to follow the instructions. Outfitted with Philadelphian Theophilus Grew’s Description and Use of the Globes (1753), I had worked with the curators at the American Philosophical Society to solve a beginner problem on one of their early terrestrials, and between the antique language and the fact that some prior curator had incorrectly locked the globe into a permanent axial tilt, we felt downright triumphant when we finally got it.

A second means was to include images of globes. I located a lovely engraving of a terrestrial globe from Englishman Benjamin Martin’s Description and Use of Both the Globes, an eighteenth-century manual popular on both sides of the Atlantic. It depicts not just the globe’s functional accessories—the brazen meridian, horizon ring, quadrant of altitude, hour circle—but also the geographical and astronomical information printed and engraved on those accessories that enabled problem-solving. So much for the vague mental image of an “antique” globe, set in some elegant but merely ornamental library stand. 

Then in proofreading the typeset manuscript—having received the boilerplate warning “Note that, at this stage in production, we can correct only typographical, grammatical, or factual errors”—I noticed a potential problem with that image. The orb is tilted. If you didn’t know better, you’d swear it was tilted on the earth’s axis, just like a modern globe. The image appeared to undercut the very fact base of my article. 

I was pretty sure I knew what this was all about, but there was only one way to be certain. I turned to my own problem-solving globe—a late-model for this sort of thing, dating from about 1870—and I manually “rectified” it to 51 degrees, the latitude of London. Now it looked just like the image in Martin’s manual. It depicted a globe not tilted on its axis, but instead fixed in the position for solving problems from the point of view of an observer in the English capital. Off went an emergency caption edit. Problem solved.

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