The 16th Century Sun Dial At St Mary's
|The mass dial at St Mary's church North Mymms|
Image from Mike Allen, from the Images of North Mymms collection
According to local photographer and historian Mike Allen, who has researched the North Mymms mass dial, they are typically circles, usually about six inches in diameter, with lines radiating from a central hole.
A wooden or metal peg, called a gnomon, was put in the hole, and its shadow marked the time of day. There were marks which gave the times for services, including morning mass, noon, and vespers (evensong).
Mike has illustrated his article (embedded below) with photographs and drawings from his Images of North Mymms collection.