branch of study: optics
Whilst being recognised as one of Germany's poets of the Romantic era, Goethe was also a romantic natural philosopher and natural scientist, just as one would expect from a polymath. One of his key areas of interest were chromatics, the teaching on colours. Amongst other instruments he used the water prism to find arguments against the Newtonian theory of colours by means of experiment – but did not succeed.
He used several different liquids with different refractive indices for his experiments to see the differences in the emerging spectra of sun light.