Stranica 129 [129]
OCR
COLOURS IN STILL WATER 71 imposed one upon the other, though, by reason of the great difference in distance of the objects forming them, it is not easy to look at both at once. The clouds, being so far off, demand a different adjustment of the eyes to that needed for the objects at his feet, so that, on looking from one picture to the other, he is conscious of an actual movement of the eyes. Now if, instead of looking straight down into the water, the line of vision be gradually inclined, the one picture will be found to gain in strength, and the other to fade rapidly away; in other words, the reflexion of the sky becomes more distinct, whilst the bottom disappears. 1hus the principle illustrated in Figs. 25, pp. 63 and 64, is verified, viz., that the more obliquely one looks at the still surface of a sheet of water, the . more will the eye receive of reflected and the less of refracted rays. As the gaze is turned farther away from the feet, the picture of the sky formed by reflexion, which has the great advantage of being far the more luminous, predominates so rapidly over the other that at a distance of a few yards, say ten, it has entirely supplanted it. It might be objected that the increased depth of water would alone account for this, but the change will be found to be just as remarkable, or very nearly so, on looking in a direction parallel to the shore, where the depth remains practically the same. Exactly the same principle applies in the case of deeper or less clear water, where, looking down at it, we do not see the bottom, but we do see the colour of the water. We have, as before, the picture of the sky formed by rays reflected at the surface superimposed upon the other picture, formed by rays coming
