Nor over-marvellous must this be deemed In these affairs that, though the films which strike Upon the eyes cannot be singly seen, The things themselves may be perceived. For thus When the wind beats upon us stroke by stroke And when the sharp cold streams, 'tis not our wont To feel each private particle of wind Or of that cold, but rather all at once; And so we see how blows affect our body, As if one thing were beating on the same And giving us the feel of its own body Outside of us. Again, whene'er we thump With finger-tip upon a stone, we touch But the rock's surface and the outer hue, Nor feel that hue by contact--rather feel The very hardness deep within the rock. Now come, and why beyond a looking-glass An image may be seen, perceive. For seen It soothly is, removed far within. 'Tis the same sort as objects peered upon Outside in their true shape, whene'er a door Yields through itself an open peering-place, And lets us see so many things outside Beyond the house. Also that sight is made By a twofold twin air: for first is seen The air inside the door-posts; next the doors, The twain to left and right; and afterwards A light beyond comes brushing through our eyes, Then other air, then objects peered upon Outside in their true shape. And thus, when first The image of the glass projects itself, As to our gaze it comes, it shoves ahead And drives along the air that's in the space Betwixt it and our eyes, and brings to pass That we perceive the air ere yet the glass. But when we've also seen the glass itself, Forthwith that image which from us is borne Reaches the glass, and there thrown back again Comes back unto our eyes, and driving rolls Ahead of itself another air, that then 'Tis this we see before itself, and thus It looks so far removed behind the glass. Wherefore again, again, there's naught for wonder *****