In the Hunterian Museum at the University of Glasgow are two pitch-based demonstrations by Lord Kelvin from the 19th century. Kelvin placed some bullets on top of a dish of pitch, and corks at the bottom: over time, the bullets sank and the corks floated.
Lord Kelvin also showed that the pitch flows like glaciers, with a mahogany ramp that allowed it to slide slowly downward and form shapes and patterns similar to glaciers in the Alps. This model was considered as an inspiration for the expected properties of luminiferous aether.