With this scale of colored lights scientists have made delicate experiments. They have analysed the colors more exactly; discovering, that is to say, the distinct degrees of color, for instance, between the red and the orange, as the one passes into the other; and again between the orange and the yellow, the yellow and the green, and so on. Then, after discovering the succession of monochromatic tints, as they call them, by optical instruments, they have tested the power of the human eye to discriminate, or detect the difference between these various tints. Notwithstanding that the difference between the latter is so slight, they have found that the eye is sensitive to something like two million monochromatic tints. I mention it not to trouble you with figures but to stir your imagination; for such a fact should fill us with admiration not only of the marvellous qualities of light but also of the marvellous capacity of the human eye. It helps us to begin to realise the miracle of light and the immense field of study that lies open to the artist who is a colorist, to whom, that is to say, it is the color of the visible world that most appeals.