There was no mistake: there was the down rising up against the sky--a huge dusky mountainous hill, exactly the same in outline as I remembered it, quite familiar, and yet entirely strange. There was the old barn near the foot of the slope; above it the black line of a low hedge and mound; on the summit the same old clump of trees; and lastly, a tall column of black smoke rising upwards, as if from a steam plough at work. It was all just the same, but lifted up into the air--the hill grown into a mountain. A second and longer gaze failed to discover the explanation of the apparition: the eye was completely deceived, and yet the mind was not satisfied. But upon getting up into the gap of the hedge, so as to obtain a better view from the mound, the cause of the illusion was at once visible. Looking through the gap was like looking through a narrow window, only a short section of the hill being within sight; from the elevation of the mound the whole range of hills could be seen at the same time. Then it became immediately apparent that on either side of this great mountain the continuation of the down right and left remained still at its former level. Upon the central hill a cloud was resting, and had for the time taken its exact shape. The ridge itself was dark, and the dark grey vapour harmonised precisely with its hue; so that the real hill and the cloud merged into each other. Either the barn and clump of trees were reproduced or perhaps enlarged and distorted by the refraction: the seeming column of smoke was a fragment of a blacker colour which chanced to be in a nearly perpendicular position. Even when recognised as such, the illusion was still perfect; nor could the eye separate the hill from the unsubstantial vapour. As I watched it, the apparent column of smoke bent, and its upper part floated away, enlarging just as smoke, its upward motion overcome by the wind, slowly yields to the current. Soon afterwards the light breeze stretched out one end of the mass of cloud, began to roll up the other, and presently lifted it, revealing the real ridge beneath, which grew momentarily more distinctly defined. Finally, the misty bank hung suspended over the down, and slowly sailed eastwards with the wind. Some time afterwards I saw a similar mirage-like enlargement of the down by cloudy vapour resting on it and assuming its contour; but the illusion was not so perfect, because seen from a more open spot, allowing an extended view of the range, and because the cloud was lighter in colour than the hill to which it clung.