Leonardo da Vinci's tensile strength tests: Implications for the discoveryof engineering mechanics

In one of Leonardo Da Vinci's notebooks, an experiment is described where s trengths in tension are measured for various lengths of wire. The notebook indicates that the results of these experiments were that longer wires were weaker than shorter wires. This result defies classical mechanics of mater ials. This conflict has been explained as a note-taking failure by Leonardo . This short note develops an alternative explanation, based on the likely heterogeneity of the mechanical properties of the wire and elementary proba bility theory. This latter explanation has implications for the difficulty and delays experienced by early investigators into the mechanics of materia ls.