Charnizay's Mass Dials

Looking at the Charnizay canonical sundials 

(which no longer function because they predate the big 15th century buttresses).

Sundials on the church at Charnizay.

On the south facing exterior wall of the church in Charnizay are the remnants of four canonical sundials (only one of them still clear). In English they are also known as mass dials or scratch dials, in French they are called cadrans canonials. The purpose of these is not for the general public to tell the time per se, but for the priest to know when to perform the daily cycle of services. They date from the Middle Ages, maybe the 12th century. They are semi-circles, divided into six, eight or twelve sectors and vary according to the season. When they were etched into the wall the church only had small buttresses, but nowadays the sundials are in the shade of more massive buttresses added in the 15th century.

 

The use of mass dials began in the 7th century and continued until the 14th century. The lines don't correspond to the hours of the day as we know them, but to liturgical times, seasonally and geographically adjusted. They are usually a semi-circle, with a hole for a wooden stick where the  radiating hour lines intersect. The sticks are always long gone, but their function was to cast a shadow so you knew what the canonical time was. Many mass dial enthusiasts recount finding a small stick and putting it in the hole, almost like a reflex action.

In the 6th and 7th centuries every congregation had their own rites and the number of divisions on the first canonical dials varied. Around the 8th century the Rule of Saint Benedict established a standard set of seven ceremonies or 'hours'. They were Matins/Lauds (midnight/before dawn), Prime (sunrise), Terce, Sext (noon), None, Vespers (sunset), and Compline (end of the day). These canonical hours do not have a temporal hour number associated with them, as they vary according to the seasons.

The canonical dials are positioned at head height, usually near the entrance. On grander churches they may be carved with care, but more often, and on little rural churches, they are crude and difficult to distinguish from graffiti. 

It was towards the end of the 7th century, under the influence of the Venerable Bede in England, that canonical dials became widespread. Monks from England, Scotland and Ireland disseminated the practice throughout Europe.

Canonical dials continued to be used right into the 16th century, but by the 14th century the bigger churches and cathedrals started using clocks and the mass dials were slowly abandoned except in small rural churches.

There are around 1500 canonical dials still visible in France, mainly in Normandy, the Touraine and Charente, and in monasteries associated with the Camino de Santiago (Fr. chemin de Compostelle).