These experiments may be repeated with coloured glasses, by causing the sun-light to shine through them on coloured surfaces. In every instance similar results will appear.
The same effect takes place when we look on coloured objects through coloured glasses; the colours being thus according to the same conditions enhanced, subdued, or neutralized.
If the prismatic colours are suffered to pass through coloured glasses, the appearances that take place are perfectly analogous; in these cases more or less force, more or less light and dark, the clearness and cleanness of the glass are all to be allowed for, as they produce many delicate varieties of effect: these will not escape the notice of every accurate observer who takes sufficient interest in the inquiry to go through the experiments.
It is scarcely necessary to mention that several coloured glasses, as well as oiled or transparent papers, placed over each other, may be made to produce and exhibit every kind of intermixture at pleasure.