500093 Turned Armilla, Hungary, c.1500 BC (bronze, wrought) by Bronze Age (2000-600 BC); h:12.45 w:10.40 cm; Cleveland Museum of Art, OH, USA; (add.info.: Europe. As the spiral mimics forms found in nature - specifically in nautilus shells - it is the basis for logarithmic measures of progression in measurement and growth, which in turn help establish the Fibonacci sequence. Through this sequence we can analyze the phenomenon of spiral designs, specifically in nautilus shells, where the radius of each new chamber grows at a rate determined by a specific proportion to the previous one. ); Purchase from the J. H. Wade Fund; out of copyright.