Sweet, beautiful vibrations exist for my touch, even though they travel through other substances than air to reach me. So I imagine sweet, delightful sounds, and the artistic arrangement of them which is called music, and I remember that they travel through the air to the ear, conveying impressions somewhat like mine. I also know what tones are, since they are perceptible tactually in a voice. Now, heat varies greatly in the sun, in the fire, in hands, and in the fur of animals; indeed, there is such a thing for me as a cold sun. So I think of the varieties of light that touch the eye, cold and warm, vivid and dim, soft and glaring, but always light, and I imagine their passage through the air to an extensive sense, instead of to a narrow one like touch. From the experience I have had with voices I guess how the eye distinguishes shades in the midst of light.