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made up of the variable combinations of experience. They retain more firmly their distinct character than in the other senses, and are enlarged under a more directly guided effort. Vision contains the largest amount of completely absorbed judgments, judgments that turn on general principles, and are early taken up in an inseparable way with the percept it n. The presence of these inferences are not only disclosed by the mistakes we make under them, when our data are insufficient, as in determining distances and relations under novel circumstances but also by various contrivances by which we alter the conditions of sight, and so the apparent position and magnitude of objects.

When we roll up a piece of paper like a funnel, and view a painting through it with one eye, the perspective is brought out more strongly. The increased effect of this monocular vision is due to the fact, that surrounding objects are cut off, the actual distance of the canvas, so distinctly given by both eyes, is obscured, and the data of the painting alone are present. The eye, relieved from the contradiction of near objects, proceeds at once to construct the landscape under the suggestions of the painter, with its true dimensions. A mask looked at in this way in the rear may, by an instant, unobserved transfer of light and shade from one side of the face to the other, be constructed with its features in relief, as if seen in front.

In the skeleton form of a stereoscope, in which two pictures of the same object are separated by a card, so that one image is seen exclusively by one eye, and the other by the other eye, the two eyes unite to construct the view at a distance, as if they were looking at remote, real objects, in reference to which the card between the eyes would present no embarrassment. The eyes being restricted in vision, being set free from the contradiction of surrounding facts, each takes up its own representation in a sort of double