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View of a guinea pig foetus and placenta
King Henry IV of England
Commercial Road
towards two young ladies
Roundel for use in optical experiments Product:Postcard View of a guinea pigPlate 9 figure 2 from the paper "New experiments on the ocular spectra of light and colours", by Robert Waring Darwin, Philosophical Transactions of the Royal Society, vol. 76 (1786), pp. 313 348. Roundel intended for use in exploring colour perception. In the written experiment circular pieces of silk are overlaid in the sequence blue (outer), yellow, pink, green and indigo (inner) with a central spot. "look steadily for a minute on this central
