The polychromatic decoration of the Egyptians is to be explained, like that of the Assyrians, of the Greeks, of the Italians, and of all other southern nations, by the quality and quantity of their daylight and the way in which it affected their visual organs. The more intense the light, the more pleasure does the eye receive from strength and variety of colour. The science of optics gives us an explanation of this fact, but at present we are concerned only with the fact itself, which is a matter of daily experience. It is notorious that the colours of birds and butterflies, and of the petals of flowers, become brighter and gayer in exact proportion as we near the equator and leave the pole;[109] the same rule holds good with the habitations of mankind, with his clothes and furniture, which become more brilliant in colour, and more audaciously abrupt in their transitions from one hue to another. Delicate shades of difference are imperceptible by an eye blinded with the southern sun; it sees nothing but the simplest, strongest, and frankest colour notes to the exclusion of all half-tint.[110] [109] We here speak of the fauna as a whole, disregarding particular genera and species. It may be said that some particular plant which is to be found both in France and Norway, is much brighter in colour when it grows in the neighbourhood of the pole than in our temperate climate, but this apparent exception only confirms the rule which we have laid down. The plant whose whole season of bloom is comprised between a late spring and an early autumn develops itself much more rapidly than with us, and, granting that it has become so hardened that it is able to resist the long and hard frosts of winter, it receives, during the short summer, much more light and sun than its French or German sister. During those fleeting summers of the north, whose strange charm has been so often described, the sun hardly descends below the horizon; the nights are an hour long, and not six or seven. The colour of flowers is therefore in exact proportion to the amount of light which they receive. [110] This was perceived by Goethe. In art, as in natural science, he divined beforehand some of the discoveries of our century by the innate force of his genius. He was not surprised by the discovery that the temples of classic Sicily were painted in brilliant tones, which concealed the surface of their stone and accentuated the leading lines of their architecture. He was one of the first to accept the views of Hittorf and to proclaim that the architects who had found traces of colours upon the mouldings of Greek buildings were not deceiving themselves and others.