Roundel for use in optical experiments Finish:Pack of 20 View of the Royal Exchange

View of the Royal Exchange fire

Early versions had a tendency to 'lift' at the front when approaching the top speed of almost 160 mph

'Cardwell's Collapse'

a shrub native to Australia and first collected by Sir Joseph Banks

Roundel for use in optical experiments Finish:Pack of 20 View of the Royal ExchangePlate 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