yellow spot than in the surrounding retina. But I find the experiment
difficult, and I hope for better results from more accurate observers.

***

On the Theory of Compound Colours with reference to Mixtures of
Blue and Yellow Light.

James Clerk Maxwell


[From the _Report of the British Association_, 1856.]


When we mix together blue and yellow paint, we obtain green paint.
This fact is well known to all who have handled colours; and it is
universally admitted that blue and yellow make green. Red, yellow,
and blue, being the primary colours among painters, green is regarded
as a secondary colour, arising from the mixture of blue and yellow.
Newton, however, found that the green of the spectrum was not the same
thing as the mixture of two colours of the spectrum, for such a
mixture could be separated by the prism, while the green of the
spectrum resisted further decomposition. But still it was believed
that yellow and blue would make a green, though not that of the
spectrum. As far as I am aware, the first experiment on the subject
is that of M. Plateau, who, before 1819, made a disc with alternate
sectors of prussian blue and gamboge, and observed that, when
spinning, the resultant tint was not green, but a neutral gray,
inclining sometimes to yellow or blue, but never to green.
Prof. J. D. Forbes of Edinburgh made similar experiments in 1849, with