Roundel for use in optical experiments Size:XL: 80 x 80cm One putto holds a scroll

One putto holds a scroll bearing the legend: 'Ecce Philosophorum Princeps'

massed tents stretch along the French coast

the purple martin

( Mr Punch)

Campbell (second from the left)

Roundel for use in optical experiments Size:XL: 80 x 80cm One putto holds a scrollPlate 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