6. REULEAUX TRIANGLE WINDOW

A Reuleaux triangle is a figure made up of three circular arcs as illustrated by this window. Each vertex is the centre of the opposite arc. The figure has some mathematical interest in that it has ‘constant width’. This means that it will roll between two fixed parallel lines. There are other figures having this property.

The configuration involving the upper two arcs is characteristic of the Gothic style of architecture. However, even in Gothic buildings the Reuleaux triangle window is surprisingly rare. The illustrated window is in Scots Church, Adelaide, Australia. Another nice example is found in the Bruges Notre Dame Eglise, Belgium.

http://en.wikipedia.org/wiki/Reuleaux_triangle



    

   – Paul Scott