“Who can venture to imitate, by the pencil, the endless varieties of red and orange and yellow which the setting sun discloses, and the magical illusions which all the day diversify the vast and varied space the eye travels over in rising gradually from the horizon to the upper sky? Those who have paid any attention to colours, must be aware of the difficulty of describing the various tints and shades that appear, and which are known to amount to many thousands.” The rapid changes of colour which the clouds undergo, seem to depend on something more than change of position either in the cloud or in the sun. Forster mentions an instance of some detached cirro-cumuli being of a fine golden yellow, but in a single minute becoming deep red. On another occasion he saw the exact counterpart in a cirro-stratus, by its instantly changing from a beautiful red to a bright golden yellow. “What, indeed, can be more interesting, than when by the breaking out of the sun in gleams, a cloud which a moment before seemed only an unshapened mass devoid of all interest and beauty, is suddenly pierced by cataracts of light, and imbued with the most splendid colours, varying every instant in intensity? Numerous examples occur of this beautiful play of colour, which cannot but remind us of the phenomena displayed by the pigeon’s neck and the peacock’s tail, by opal and pearl. “After the sun is set, the mild glow of his rays is still diffused over every part; and it has been remarked, that the clouds assume their brightest and most splendid colours a few minutes after it is below the horizon. It is in the finest weather that the colouring of the sky presents the most perfect examples of harmony, in tempestuous weather it being almost always inharmonious. At the time of a warm sun-setting, the whole hemisphere is influenced by the prevailing colour of the light. The snowy summits of the Alps appear about sunset of a most beautiful violet colour, approaching to light crimson or pink. It is remarkable, also, as an example of that general harmony which prevails in the material world, that the most glowing and magnificent skies occur when terrestrial objects put on their deepest and most splendid hues. It has also been observed, that it is not the change of vegetation only, which gives to the decaying charms of autumn their finest and most golden hues, but also the atmosphere and the peculiar lights and shadows which then prevail; and there can be no doubt, on the other hand, that our perception of beauty in the sky is very much influenced by the surrounding scenery. In autumn all is matured; and the rich hues of the ripened fruits and the changing foliage are rendered still more lovely by the warm haze which a fine day at that season presents. So, also, the earlier hues of spring have a transparency, and a thousand quivering lights, which in their turn harmonize with the light and flitting clouds and uncertain shadows which then prevail.” {155}