In this horizontal sundial in France, streaks of light are used to read the sundial.
The streaks are produced each hour by the central system of metal sheets.
It is easy to see that the main direction of all those sheets is equal to the direction of an ordinary pole style.
On each hour, the sun is in a specific shadow plane.
The sheets are so arranged that every hour, for a short time, the sun can shine through the openings between the sheets, producing a streak of light.
There are a large number of cut-aways in the construction. They form the word equinoxe around the beginning of spring and autumn, and the word solstice around the beginning of summer and winter.
This streak-of-light sundial is less suited to read intervening time. For this reason, there is an ordinary sundial on the other side, as shown below.
Fer de Vries
Design: Jean Salins de Marseille
Address: Ecole des Mines, Sophia Antipolis, Frankrijk
English translation: RH