Some scribbles dismissed in the 1920s by the then-director of the Victoria & Albert Museum as “irrelevant notes and diagrams in red chalk” were recently revealed to represent Leonardo da Vinci’s first record of the laws of friction. The University of Cambridge announced the findings on July 21.

Although Guillaume Amontons published his laws of friction in 1699, Leonardo had investigated friction about 200 years earlier within his notebooks and through experiments. This precedent by Leonardo is well-known by tribologists, yet the new research by Ian Hutchings, professor of manufacturing engineering at the University of Cambridge, gives Leonardo’s friction work more depth and its first chronological study. Hutchings’s full paper on “Leonardo da Vinci’s studies of friction” is in the August issue of Wear journal (and online in a free PDF).

You can see the significant sketches in the above page from the 1493 Codex Forster, now in the collections of the Victoria & Albert Museum. What might immediately catch the eye is an old woman in profile with a quote from Petrarch — “cosa bella mortal passa e non dura” (“mortal beauty passes and does not last”) — beneath her visage. (The words read left-to-right, in keeping with Leonardo’s “mirror writing.”) The sketch is what initially interested 1920s art historians, although speculation rested on her identity, possibly as an ironically withered Helen of Troy. Yet below is something even more important, with geometric shapes and red notes seeming to represent a friction experiment.

Hutchings stated in the release:

The sketches and text show Leonardo understood the fundamentals of friction in 1493. He knew that the force of friction acting between two sliding surfaces is proportional to the load pressing the surfaces together and that friction is independent of the apparent area of contact between the two surfaces. These are the ‘laws of friction’ that we nowadays usually credit to a French scientist, Guillaume Amontons, working two hundred years later. […] Leonardo’s 20-year study of friction, which incorporated his empirical understanding into models for several mechanical systems, confirms his position as a remarkable and inspirational pioneer of tribology.

The mingling of art with science wasn’t unusual for Leonardo, as Hutchings explains in his paper that the polymath had a “frugal use and re-use of paper” for “both writing and sketches to record his thoughts.” It can seem like there’s no end to discoveries from the incredible notebooks he left behind, whether a sketch for an early refrigerator, a curious viola organista instrument, or a strangely erased nude. This most recent find emphasizes that these historic texts are still worthy of investigation, as revelations might remain hidden in the margins.

h/t Phys.org

Read more about Leonardo da Vinci and friction in Ian Hutchings’s article in the August issue of Wear journal (or online in a free PDF).