Pendulum, photographed on February 17, 1933

Pendulum, photographed on February 17th, 1933. University of Rennes professor Paul-Marcel Le Rolland’s and Jean-Louis Foune’s pendulum was an instru¬ment designed to analyze frameworks so as to evaluate the constructions’ rigidity. The device was based on theprinciple of associated pendulums.The two inventors’ patent was publi¬shed in March 1927. The device consisted of “perfecting the processes and devices that measure the hard¬ness of a material.” The inventors explained that, for this purpose, they compared the movements of two pendulums. The first was equip¬ped with a knife or elastic blade, oscil¬lating at a fixed rate. The other had a convex surface that oscillated on top of a sample of the studied material. The comparison of these two move¬ments allowed the measurement of the sample’s relative hardness. Office national des recherches scientifiques et industrielles et des inventions.