Leonardo Da Vinci's Tensile Strength Tests: Implications for the Discovery of Engineering Mechanics

In one of Leonardo Da Vinci's notebooks, an experiment is described where strengths 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 de®nes classical mechanics of materials. This con ̄ict 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 probability theory. This latter explanation has implications for the diculty and delays experienced by early investigators into the mechanics of materials.