"Isler’s form-finding method of the reversed hanging cloth was discovered serendipitously in the summer of 1955. On a building site he saw a piece of wet burlap draped over a mesh of steel bars. He noticed that within one square opening, the burlap hung in a domelike shape under its own weight. Isler concluded that the cloth carried itself in pure tension, so that when it was reversed it would become a form in pure compression. ...the three-dimensional version of Hooke’s discovery; a piece of cloth that is hung from several fixed points will create an ideal form that is completely in tension. If the shape is “frozen” and flipped, the resulting shell should be in complete compression, which is convenient for concrete structures since concrete performs well in compression but poorly in tension. The main difference between the work of Gaudí and Isler is that the Spanish architect found his form through a network of two-dimensional catenary shapes while the Swiss engineer only used one hanging element (a piece of fabric) to determine the ideal form of his structure."