I begin with one of the simpler instruments, a volvelle marking the horizon. Volvelles are spinning wheels and one of the most popular moving features in books, then and now. Because it doesn’t require a lot of technical stuff, the designer has filled up all the space with art: a man standing upright pointing to the zenith; mountains, waters, and houses on the little Earth; and lovely swirls and an angel below the horizon.
The next volvelle is a lunar clock. You set the phase of the moon in the little window, then use the angle of the moon to determine the location of the sun at night, and thus the time. The little pointers for sun and moon are decorated with their little smiling icons, while a spangling of stars and suns enhance the border.
These first three examples all come from 1533, from a very popular book made by the mathematical instrument-maker Gemma Frisius, which was an enlarged edition of Petrus Apianus’s Cosmographia. Apianus called this instrument “Ptolemy’s Instrument,” and it is used to tell the time, plus the times of sunrise and sunset in any latitude. Note the grinning face decorating the center. I don’t know for sure about the strings, but I’m guessing one was to have a weight attached for use as a plumb. Some sundials also used a string as a gnomen. One advantage of instruments printed in books was that their instructions for use were always right there with them, as long as you read Latin.
I include this next one to show how printed pieces could be cut out, mounted to something stiffer, and assembled to make quite a beautiful and
respectable-looking instrument. This one does have a small weight attached. It also looks like it’s engraved, rather than wood block printed. It, too, was for telling the time based on astronomical observations. It’s by Caspar Vopel in 1552.
And finally, another instrument from Frisius, this one from a 1584 edition. It marks the path of the sun over a projection of the Earth. Note that its prime meridian is off the west coast of Africa, as established by Ptolemy, and it counts all the way around to 360° instead of plus and minus 180°. Note also the charming obligatory sailing ship in the Atlantic Ocean.
The thing is, these paper instruments are simultaneously works of beauty and utility, mass-produced relatively cheaply and yet with sufficient precision to fuel the scientific advances of their time. They’re reminders of the importance of exploration, study, and discovery, and also of the importance of popularizing science and making it more accessible to more people - seeking new horizons, and bringing them back to familiar territory. As such, I think they fit in perfectly with this summer’s hoopla over New Horizons and our new discoveries about Pluto.
[Pictures: Horizon instrument, woodcut designed by Gemma Frisius, from Petrus Apianus’s Cosmographia, 1533;
Lunar clock, woodcut designed by Frisius, from Cosmographia, 1533;
Altitude sun dial, woodcut designed by Frisius, from Cosmographia, 1533 (Images from Museum of the History of Science, Oxford);
Regiomontanus-type dial and nocturnal, engraving designed by Caspar Vopel, 1552;
Speculum cosmographicum, woodcut designed by Gemma Frisius, from Petrus Apianus’s Cosmographia, 1584 (Images from Museum of the History of Science, Oxford).]