Gnomonic Blocks, or Multi-faceted Sundials

In the park of the Abbey of Epau, in Yvré-l'Evêque in France, you can admire a curious monument in the shape of an obelisk. Built by the Benedictine monk Bedos de Celles between 1631 and 1640, the sculpture consists of four sides, perfectly symmetrical, and oriented along the cardinal directions, with several curious protrusions and shapes. Each of these shapes has a purpose: they are sundials, a total of thirty in all.

Sundial of the Groirie in Yvré-l'Evêque. Photo: Selbymay/Wikimedia Commons

Distributed over all the four faces, these sundials operate at different times of the day as the sun travels. The south face is the one with the most dials. It has, among other things, a carved block in the form of an open book, the pages of which serve as a style for eight distinct dials. Above this book are aligned six cylindrical dials. The south face also has two other vertical dials.

Each of the east and west faces has three concave dials, in the shape of a sphere or cylinder, engraved in hollow. The north face has five dials. The whole sculpture is surmounted by a concave crescent-shaped dial.

On the north face of the sculpture is inscribed in Latin: “SIMPLEX SUM SINE SOLE, NIHIL SINE LUMINE NULLUS”, meaning “I am simple without sun, nothing without light.”

The sundial at Abbey of Epau is known as a gnomonic block, which is a sculpture comprising of more than one sundial. They became very popular in Europe during the 15th and 16th centuries. Some gnomonic blocks have the advantage of receiving light at different times of the day, so it is possible to build them such that they give the time in several time zones.

Sundial of the Groirie in Yvré-l'Evêque. Photo: Stéphane Mahot/Flickr

Other historical examples of gnomonic blocks

Sundial at Mont Sainte-Odile Abbey, on Mont Sainte-Odile, one of the most famous peaks of the Vosges mountain range in the French region of Alsace. Photo: Jörgens.mi/Wikimedia Commons

Sundial at Mont Sainte-Odile Abbey, on Mont Sainte-Odile, one of the most famous peaks of the Vosges mountain range in the French region of Alsace. Photo: Tristan/Wikimedia Commons

Polyhedral sundial by Ludwig von Hohenfeld, with 17 different sundials for the region between Tubingen and Stuttgart. Made in 1596 of wood, paper, iron, brass. Currently at the Landesmuseum in Württemberg, Stuttgart, Germany. Photo: Daderot/Wikimedia Commons

A multi-faceted sundial from 1793 located at Musée dauphinois (Dauphinois Museum), in Grenoble, France. Photo: Physical data/Wikimedia Commons

This multi-faceted sundial near Roman Baths in Sanssouci Park, Potsdam, Germany, has 55 dial faces. Photo: Greg Schechter/Wikimedia Commons

Multi-faceted sundial in Barrington Court, Somerset dating from the 1920s. The sundial is built around a dodecahedron. Ten of the faces have bronze gnomons, the top face supports an upstanding lion while the tenth face is used as a support. Photo: Martinvl/Wikimedia Commons

Multi-faceted sundial in front of Abbotsford House, home of the historical novelist and poet Sir Walter Scott (1771– 1832). Photo: Ad Meskens/Wikimedia Commons