_Power of Sound over the Mind._--The power of sound to affect the mind, and especially the feelings, is too well known to require specific statement. The note of an instrument, the tone of a human voice, the wild warbling of a bird, the tinkling of a bell, the variations of speech and of song, from the high and shrill to the low and heavy intonation, from the quick and impetuous to the slow and plaintive movement, these simple varieties of tone affect powerfully the heart, and find their way at once and irresistibly to the feelings. Hence the power of music over even the uncultivated mind; hence too in no small degree the power of the skilful orator over the feelings of his audience. It is not merely, nor so much, the thing said, in many cases, as the way of saying it, that touches and sways the assembled multitude. Tones and sounds have a natural meaning. They are the natural language of the heart. They express emotion, and hence awaken emotions in others. _The Question as to Sight._--Turning now from the sense of _hearing_ to that of _sight_, the question arises, What is it precisely that we perceive by the eye? When we fix the eye upon any object, more or less remote, what is it, strictly speaking, that we see, extension and figure, or only color? Is it by vision that we learn primarily the distance of objects and their locality? These are points requiring investigation. _Does Sight give Extension and Figure._--As to the first of these questions, whether extension and figure are objects of direct visual perception. No doubt they are associated in our minds with the act of vision, so that the moment we see an object we obtain an idea of it as extended, and of such and such dimensions and figure. The question is, whether it is really through the sense of sight that we obtain this idea, or in some other way. Had we no other means of information, would sight alone give us this? When we first open our eyes on external objects, do we receive the idea of extension and figure, or only of color? The fact that as matters are, we cannot in our experience separate the notion of some surface extension from the sensation of color, is not decisive of these questions. We cannot, as Dr. Brown observes, separate the color from the convexity and magnitude of an oak before us, but this does not prove that convexity and magnitude are objects of immediate and original perception. If every surface in nature had been convex, suggests the same writer, we should probably have found the same difficulty in attempting to conceive of color as separate from convexity, that we now find in attempting to conceive of it as separate from length and breadth. As it is, however, our sensation of color has not always been associated with convexity, while it has been always associated with surface extension. Hence it is, he maintains, that we seem to perceive, by the eye, the length, and breadth, and objects along with their color.