George Eliot's "Pier-Glass": The Development of a Metaphor

Let us stand on the sea-shore on a cloudless night with a full moon over the sea and a swell on the water. Of course a long line of splendour will be seen on the waves under the moon, reaching from the horizon to our very feet. But are those waves between the moon and us actually more illuminated than any other part of the sea? Not one whit. The whole surface of the sea is under the same full light, but the waves between the moon and us are the only ones which are in a position to reflect that light to our eyes. The sea on both sides of the path of light is in perfect darkness-almost black. But is it so from shadow ? Not so,-for there is nothing to intercept the moonlight from it: it is so from position, because it cannot reflect any of the rays which fall on it to our eyes, but reflects instead the dark vault of the night sky.1