The apparatus consists of a rectangular wooden box divided into two compartments in which the weights of two metal pendulums of equal length oscillate. By filling one compartment with water or another liquid and leaving the other empty, we observe that the damping of the pendulum oscillations is proportional to the resistance of the liquid used. Jean-Antoine Nollet used an apparatus of this type to explain the operation of a rowboat. Provenance: Lorraine collections.